From b46558797598215cb1926a160d3485ab67ad06c6 Mon Sep 17 00:00:00 2001
From: John Jannotti <jj@cs.brown.edu>
Date: Tue, 7 Sep 2021 19:13:21 -0400
Subject: [PATCH 1/4] loads and stores opcodes that take scratch slot from
 stack

---
 cmd/goal/clerk.go                         |   4 +-
 cmd/tealdbg/local.go                      |  10 +-
 cmd/tealdbg/local_test.go                 |  26 ++---
 daemon/algod/api/server/v2/dryrun.go      |   2 +-
 data/transactions/logic/README.md         |  10 +-
 data/transactions/logic/TEAL_opcodes.md   |  18 ++-
 data/transactions/logic/assembler.go      |  52 ++++-----
 data/transactions/logic/assembler_test.go |   6 +-
 data/transactions/logic/debugger.go       |   2 +-
 data/transactions/logic/doc.go            |   6 +-
 data/transactions/logic/eval.go           | 127 +++++++++++++---------
 data/transactions/logic/eval_test.go      |  35 +++++-
 data/transactions/logic/opcodes.go        |   4 +
 data/transactions/verify/txn.go           |  10 +-
 ledger/eval.go                            |   2 +-
 ledger/eval_test.go                       |   2 +-
 16 files changed, 200 insertions(+), 116 deletions(-)

diff --git a/cmd/goal/clerk.go b/cmd/goal/clerk.go
index 0581703c0a..571c4d1a48 100644
--- a/cmd/goal/clerk.go
+++ b/cmd/goal/clerk.go
@@ -1087,7 +1087,7 @@ var dryrunCmd = &cobra.Command{
 			if uint64(txn.Lsig.Len()) > params.LogicSigMaxSize {
 				reportErrorf("program size too large: %d > %d", len(txn.Lsig.Logic), params.LogicSigMaxSize)
 			}
-			ep := logic.EvalParams{Txn: &txn, Proto: &params, GroupIndex: i, TxnGroup: txgroup}
+			ep := logic.EvalParams{Txn: &txn, Proto: &params, GroupIndex: uint64(i), TxnGroup: txgroup}
 			err := logic.Check(txn.Lsig.Logic, ep)
 			if err != nil {
 				reportErrorf("program failed Check: %s", err)
@@ -1095,7 +1095,7 @@ var dryrunCmd = &cobra.Command{
 			sb := strings.Builder{}
 			ep = logic.EvalParams{
 				Txn:        &txn,
-				GroupIndex: i,
+				GroupIndex: uint64(i),
 				Proto:      &params,
 				Trace:      &sb,
 				TxnGroup:   txgroup,
diff --git a/cmd/tealdbg/local.go b/cmd/tealdbg/local.go
index baebcea046..814afae3e4 100644
--- a/cmd/tealdbg/local.go
+++ b/cmd/tealdbg/local.go
@@ -209,7 +209,7 @@ type evaluation struct {
 	source          string
 	offsetToLine    map[int]int
 	name            string
-	groupIndex      int
+	groupIndex      uint64
 	pastSideEffects []logic.EvalSideEffects
 	mode            modeType
 	aidx            basics.AppIndex
@@ -387,7 +387,7 @@ func (r *LocalRunner) Setup(dp *DebugParams) (err error) {
 					r.runs[i].source = source
 				}
 			}
-			r.runs[i].groupIndex = dp.GroupIndex
+			r.runs[i].groupIndex = uint64(dp.GroupIndex)
 			r.runs[i].pastSideEffects = dp.PastSideEffects
 			r.runs[i].name = dp.ProgramNames[i]
 
@@ -431,7 +431,7 @@ func (r *LocalRunner) Setup(dp *DebugParams) (err error) {
 		if len(stxn.Lsig.Logic) > 0 {
 			run := evaluation{
 				program:    stxn.Lsig.Logic,
-				groupIndex: gi,
+				groupIndex: uint64(gi),
 				mode:       modeLogicsig,
 			}
 			r.runs = append(r.runs, run)
@@ -452,7 +452,7 @@ func (r *LocalRunner) Setup(dp *DebugParams) (err error) {
 					}
 					run := evaluation{
 						program:         stxn.Txn.ApprovalProgram,
-						groupIndex:      gi,
+						groupIndex:      uint64(gi),
 						pastSideEffects: dp.PastSideEffects,
 						mode:            modeStateful,
 						aidx:            appIdx,
@@ -488,7 +488,7 @@ func (r *LocalRunner) Setup(dp *DebugParams) (err error) {
 							}
 							run := evaluation{
 								program:         program,
-								groupIndex:      gi,
+								groupIndex:      uint64(gi),
 								pastSideEffects: dp.PastSideEffects,
 								mode:            modeStateful,
 								aidx:            appIdx,
diff --git a/cmd/tealdbg/local_test.go b/cmd/tealdbg/local_test.go
index 6a844963e5..f199d93da3 100644
--- a/cmd/tealdbg/local_test.go
+++ b/cmd/tealdbg/local_test.go
@@ -571,7 +571,7 @@ func TestDebugFromPrograms(t *testing.T) {
 	err = l.Setup(&dp)
 	a.NoError(err)
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.Nil(l.runs[0].ba)
 	a.Equal(modeLogicsig, l.runs[0].mode)
 	a.Empty(l.runs[0].aidx)
@@ -587,8 +587,8 @@ func TestDebugFromPrograms(t *testing.T) {
 	err = l.Setup(&dp)
 	a.NoError(err)
 	a.Equal(2, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
-	a.Equal(0, l.runs[1].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[1].groupIndex)
 	a.Nil(l.runs[0].ba)
 	a.Equal(modeLogicsig, l.runs[0].mode)
 	a.Empty(l.runs[0].aidx)
@@ -617,7 +617,7 @@ func TestRunMode(t *testing.T) {
 	err := l.Setup(&dp)
 	a.NoError(err)
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.NotNil(l.runs[0].ba)
 	a.Equal(modeStateful, l.runs[0].mode)
@@ -640,7 +640,7 @@ func TestRunMode(t *testing.T) {
 	err = l.Setup(&dp)
 	a.NoError(err)
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.Nil(l.runs[0].ba)
 	a.Equal(modeLogicsig, l.runs[0].mode)
@@ -659,7 +659,7 @@ func TestRunMode(t *testing.T) {
 	err = l.Setup(&dp)
 	a.NoError(err)
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.NotNil(l.runs[0].ba)
 	a.Equal(modeStateful, l.runs[0].mode)
@@ -677,7 +677,7 @@ func TestRunMode(t *testing.T) {
 	err = l.Setup(&dp)
 	a.NoError(err)
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.Nil(l.runs[0].ba)
 	a.Equal(modeLogicsig, l.runs[0].mode)
@@ -738,7 +738,7 @@ func TestDebugFromTxn(t *testing.T) {
 	err = l.Setup(&dp)
 	a.NoError(err)
 	a.Equal(1, len(l.runs))
-	a.Equal(1, l.runs[0].groupIndex)
+	a.Equal(uint64(1), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.Equal([]byte{3}, l.runs[0].program)
 	a.Nil(l.runs[0].ba)
@@ -764,7 +764,7 @@ func TestDebugFromTxn(t *testing.T) {
 	a.NoError(err)
 	a.Equal(2, len(l.txnGroup))
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.Equal([]byte{1}, l.runs[0].program)
 	a.NotNil(l.runs[0].ba)
@@ -787,7 +787,7 @@ func TestDebugFromTxn(t *testing.T) {
 	a.NoError(err)
 	a.Equal(2, len(l.txnGroup))
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.Equal([]byte{1, 1}, l.runs[0].program)
 	a.NotNil(l.runs[0].ba)
@@ -812,7 +812,7 @@ func TestDebugFromTxn(t *testing.T) {
 	a.NoError(err)
 	a.Equal(1, len(l.txnGroup))
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.Equal([]byte{4}, l.runs[0].program)
 	a.NotNil(l.runs[0].ba)
@@ -949,7 +949,7 @@ func TestLocalBalanceAdapter(t *testing.T) {
 	a.NoError(err)
 	a.Equal(2, len(l.txnGroup))
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.Equal([]byte{1}, l.runs[0].program)
 	a.NotNil(l.runs[0].ba)
@@ -1039,7 +1039,7 @@ func TestLocalBalanceAdapterIndexer(t *testing.T) {
 	a.NoError(err)
 	a.Equal(2, len(l.txnGroup))
 	a.Equal(1, len(l.runs))
-	a.Equal(0, l.runs[0].groupIndex)
+	a.Equal(uint64(0), l.runs[0].groupIndex)
 	a.NotNil(l.runs[0].eval)
 	a.Equal([]byte{1}, l.runs[0].program)
 	a.NotNil(l.runs[0].ba)
diff --git a/daemon/algod/api/server/v2/dryrun.go b/daemon/algod/api/server/v2/dryrun.go
index c2dce30961..fed86ce627 100644
--- a/daemon/algod/api/server/v2/dryrun.go
+++ b/daemon/algod/api/server/v2/dryrun.go
@@ -420,7 +420,7 @@ func doDryrunRequest(dr *DryrunRequest, response *generated.DryrunResponse) {
 			Txn:                     &stxn,
 			Proto:                   &proto,
 			TxnGroup:                dr.Txns,
-			GroupIndex:              ti,
+			GroupIndex:              uint64(ti),
 			PastSideEffects:         pse,
 			PooledApplicationBudget: &pooledAppBudget,
 		}
diff --git a/data/transactions/logic/README.md b/data/transactions/logic/README.md
index d7802ca479..098641b385 100644
--- a/data/transactions/logic/README.md
+++ b/data/transactions/logic/README.md
@@ -233,19 +233,21 @@ Some of these have immediate data in the byte or bytes after the opcode.
 | `txn f` | push field F of current transaction to stack |
 | `gtxn t f` | push field F of the Tth transaction in the current group |
 | `txna f i` | push Ith value of the array field F of the current transaction |
+| `txnas f` | push Xth value of the array field F of the current transaction |
 | `gtxna t f i` | push Ith value of the array field F from the Tth transaction in the current group |
+| `gtxnas t f` | push Xth value of the array field F from the Tth transaction in the current group |
 | `gtxns f` | push field F of the Xth transaction in the current group |
 | `gtxnsa f i` | push Ith value of the array field F from the Xth transaction in the current group |
+| `gtxnsas f` | pop an index A and an index B. push Bth value of the array field F from the Ath transaction in the current group |
 | `global f` | push value from globals to stack |
 | `load i` | copy a value from scratch space to the stack |
-| `store i` | pop a value from the stack and store to scratch space |
+| `loads` | copy a value from the Xth scratch space to the stack |
+| `store i` | pop value X. store X to the Ith scratch space |
+| `stores` | pop indexes A and B. store A to the Bth scratch space |
 | `gload t i` | push Ith scratch space index of the Tth transaction in the current group |
 | `gloads i` | push Ith scratch space index of the Xth transaction in the current group |
 | `gaid t` | push the ID of the asset or application created in the Tth transaction of the current group |
 | `gaids` | push the ID of the asset or application created in the Xth transaction of the current group |
-| `txnas f` | push Xth value of the array field F of the current transaction |
-| `gtxnas t f` | push Xth value of the array field F from the Tth transaction in the current group |
-| `gtxnsas f` | pop an index A and an index B. push Bth value of the array field F from the Ath transaction in the current group |
 | `args` | push Xth LogicSig argument to stack |
 
 **Transaction Fields**
diff --git a/data/transactions/logic/TEAL_opcodes.md b/data/transactions/logic/TEAL_opcodes.md
index 32747e61ef..8bc1dbc0a3 100644
--- a/data/transactions/logic/TEAL_opcodes.md
+++ b/data/transactions/logic/TEAL_opcodes.md
@@ -489,7 +489,7 @@ for notes on transaction fields available, see `txn`. If this transaction is _i_
 - Opcode: 0x35 {uint8 position in scratch space to store to}
 - Pops: *... stack*, any
 - Pushes: _None_
-- pop a value from the stack and store to scratch space
+- pop value X. store X to the Ith scratch space
 
 ## txna f i
 
@@ -569,6 +569,22 @@ for notes on transaction fields available, see `txn`. If top of stack is _i_, `g
 
 `gaids` fails unless the requested transaction created an asset or application and X < GroupIndex.
 
+## loads
+
+- Opcode: 0x3e
+- Pops: *... stack*, uint64
+- Pushes: any
+- copy a value from the Xth scratch space to the stack
+- LogicSigVersion >= 5
+
+## stores
+
+- Opcode: 0x3f
+- Pops: *... stack*, {any A}, {uint64 B}
+- Pushes: _None_
+- pop indexes A and B. store A to the Bth scratch space
+- LogicSigVersion >= 5
+
 ## bnz target
 
 - Opcode: 0x40 {int16 branch offset, big endian}
diff --git a/data/transactions/logic/assembler.go b/data/transactions/logic/assembler.go
index ca953ee36c..0f3dbc15ef 100644
--- a/data/transactions/logic/assembler.go
+++ b/data/transactions/logic/assembler.go
@@ -875,16 +875,16 @@ func assembleGtxn(ops *OpStream, spec *OpSpec, args []string) error {
 		return ops.error(err)
 	}
 	if slot > 255 {
-		return ops.errorf("gtxn transaction index beyond 255: %d", slot)
+		return ops.errorf("%s transaction index beyond 255: %d", spec.Name, slot)
 	}
 
 	fs, ok := txnFieldSpecByName[args[1]]
 	if !ok {
-		return ops.errorf("gtxn unknown field: %#v", args[1])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[1])
 	}
 	_, ok = txnaFieldSpecByField[fs.field]
 	if ok {
-		return ops.errorf("found array field %#v in gtxn op", args[1])
+		return ops.errorf("found array field %#v in %s op", args[1], spec.Name)
 	}
 	if fs.version > ops.Version {
 		return ops.errorf("field %#v available in version %d. Missed #pragma version?", args[1], fs.version)
@@ -905,38 +905,38 @@ func assembleGtxn2(ops *OpStream, spec *OpSpec, args []string) error {
 		gtxna := OpsByName[ops.Version]["gtxna"]
 		return assembleGtxna(ops, &gtxna, args)
 	}
-	return ops.error("gtxn expects two or three arguments")
+	return ops.errorf("%s expects two or three arguments", spec.Name)
 }
 
 func assembleGtxna(ops *OpStream, spec *OpSpec, args []string) error {
 	if len(args) != 3 {
-		return ops.error("gtxna expects three arguments")
+		return ops.errorf("%s expects three arguments", spec.Name)
 	}
 	slot, err := strconv.ParseUint(args[0], 0, 64)
 	if err != nil {
 		return ops.error(err)
 	}
 	if slot > 255 {
-		return ops.errorf("gtxna group index beyond 255: %d", slot)
+		return ops.errorf("%s group index beyond 255: %d", spec.Name, slot)
 	}
 
 	fs, ok := txnFieldSpecByName[args[1]]
 	if !ok {
-		return ops.errorf("gtxna unknown field: %#v", args[1])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[1])
 	}
 	_, ok = txnaFieldSpecByField[fs.field]
 	if !ok {
-		return ops.errorf("gtxna unknown field: %#v", args[1])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[1])
 	}
 	if fs.version > ops.Version {
-		return ops.errorf("gtxna %#v available in version %d. Missed #pragma version?", args[1], fs.version)
+		return ops.errorf("%s %#v available in version %d. Missed #pragma version?", spec.Name, args[1], fs.version)
 	}
 	arrayFieldIdx, err := strconv.ParseUint(args[2], 0, 64)
 	if err != nil {
 		return ops.error(err)
 	}
 	if arrayFieldIdx > 255 {
-		return ops.errorf("gtxna array index beyond 255: %d", arrayFieldIdx)
+		return ops.errorf("%s array index beyond 255: %d", spec.Name, arrayFieldIdx)
 	}
 
 	ops.pending.WriteByte(spec.Opcode)
@@ -949,7 +949,7 @@ func assembleGtxna(ops *OpStream, spec *OpSpec, args []string) error {
 
 func assembleGtxnas(ops *OpStream, spec *OpSpec, args []string) error {
 	if len(args) != 2 {
-		return ops.error("gtxnas expects two immediate arguments")
+		return ops.errorf("%s expects two immediate arguments", spec.Name)
 	}
 
 	slot, err := strconv.ParseUint(args[0], 0, 64)
@@ -957,19 +957,19 @@ func assembleGtxnas(ops *OpStream, spec *OpSpec, args []string) error {
 		return ops.error(err)
 	}
 	if slot > 255 {
-		return ops.errorf("gtxnas group index beyond 255: %d", slot)
+		return ops.errorf("%s group index beyond 255: %d", spec.Name, slot)
 	}
 
 	fs, ok := txnFieldSpecByName[args[1]]
 	if !ok {
-		return ops.errorf("gtxnas unknown field: %#v", args[1])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[1])
 	}
 	_, ok = txnaFieldSpecByField[fs.field]
 	if !ok {
-		return ops.errorf("gtxnas unknown field: %#v", args[1])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[1])
 	}
 	if fs.version > ops.Version {
-		return ops.errorf("gtxnas %#v available in version %d. Missed #pragma version?", args[1], fs.version)
+		return ops.errorf("%s %#v available in version %d. Missed #pragma version?", spec.Name, args[1], fs.version)
 	}
 
 	ops.pending.WriteByte(spec.Opcode)
@@ -985,11 +985,11 @@ func assembleGtxns(ops *OpStream, spec *OpSpec, args []string) error {
 		return assembleGtxnsa(ops, &gtxnsa, args)
 	}
 	if len(args) != 1 {
-		return ops.error("gtxns expects one or two immediate arguments")
+		return ops.errorf("%s expects one or two immediate arguments", spec.Name)
 	}
 	fs, ok := txnFieldSpecByName[args[0]]
 	if !ok {
-		return ops.errorf("gtxns unknown field: %#v", args[0])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[0])
 	}
 	_, ok = txnaFieldSpecByField[fs.field]
 	if ok {
@@ -1007,25 +1007,25 @@ func assembleGtxns(ops *OpStream, spec *OpSpec, args []string) error {
 
 func assembleGtxnsa(ops *OpStream, spec *OpSpec, args []string) error {
 	if len(args) != 2 {
-		return ops.error("gtxnsa expects two immediate arguments")
+		return ops.errorf("%s expects two immediate arguments", spec.Name)
 	}
 	fs, ok := txnFieldSpecByName[args[0]]
 	if !ok {
-		return ops.errorf("gtxnsa unknown field: %#v", args[0])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[0])
 	}
 	_, ok = txnaFieldSpecByField[fs.field]
 	if !ok {
-		return ops.errorf("gtxnsa unknown field: %#v", args[0])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[0])
 	}
 	if fs.version > ops.Version {
-		return ops.errorf("gtxnsa %#v available in version %d. Missed #pragma version?", args[0], fs.version)
+		return ops.errorf("%s %#v available in version %d. Missed #pragma version?", spec.Name, args[0], fs.version)
 	}
 	arrayFieldIdx, err := strconv.ParseUint(args[1], 0, 64)
 	if err != nil {
 		return ops.error(err)
 	}
 	if arrayFieldIdx > 255 {
-		return ops.errorf("gtxnsa array index beyond 255: %d", arrayFieldIdx)
+		return ops.errorf("%s array index beyond 255: %d", spec.Name, arrayFieldIdx)
 	}
 	ops.pending.WriteByte(spec.Opcode)
 	ops.pending.WriteByte(uint8(fs.field))
@@ -1036,18 +1036,18 @@ func assembleGtxnsa(ops *OpStream, spec *OpSpec, args []string) error {
 
 func assembleGtxnsas(ops *OpStream, spec *OpSpec, args []string) error {
 	if len(args) != 1 {
-		return ops.error("gtxnsas expects one immediate argument")
+		return ops.errorf("%s expects one immediate argument", spec.Name)
 	}
 	fs, ok := txnFieldSpecByName[args[0]]
 	if !ok {
-		return ops.errorf("gtxnsas unknown field: %#v", args[0])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[0])
 	}
 	_, ok = txnaFieldSpecByField[fs.field]
 	if !ok {
-		return ops.errorf("gtxnsas unknown field: %#v", args[0])
+		return ops.errorf("%s unknown field: %#v", spec.Name, args[0])
 	}
 	if fs.version > ops.Version {
-		return ops.errorf("gtxnsas %#v available in version %d. Missed #pragma version?", args[0], fs.version)
+		return ops.errorf("%s %#v available in version %d. Missed #pragma version?", spec.Name, args[0], fs.version)
 	}
 	ops.pending.WriteByte(spec.Opcode)
 	ops.pending.WriteByte(uint8(fs.field))
diff --git a/data/transactions/logic/assembler_test.go b/data/transactions/logic/assembler_test.go
index 1d8ff50973..139cbf101b 100644
--- a/data/transactions/logic/assembler_test.go
+++ b/data/transactions/logic/assembler_test.go
@@ -324,6 +324,10 @@ int 0
 gtxnsas ApplicationArgs
 int 0
 args
+int 0
+loads
+int 0
+stores
 `
 
 var nonsense = map[uint64]string{
@@ -339,7 +343,7 @@ var compiled = map[uint64]string{
 	2: "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",
 	3: "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",
 	4: "042004010200b7a60c26040242420c68656c6c6f20776f726c6421208dae2087fbba51304eb02b91f656948397a7946390e8cb70fc9ea4d95f92251d047465737400320032013202320380021234292929292a0431003101310231043105310731083109310a310b310c310d310e310f3111311231133114311533000033000133000233000433000533000733000833000933000a33000b33000c33000d33000e33000f3300113300123300133300143300152d2e01022581f8acd19181cf959a1281f8acd19181cf951a81f8acd19181cf1581f8acd191810f082209240a220b230c240d250e230f23102311231223132314181b1c28171615400003290349483403350222231d4a484848482a50512a632223524100034200004322602261222b634848222862482864286548482228236628226724286828692422700048482471004848361c0037001a0031183119311b311d311e311f312024221e312131223123312431253126312731283129312a312b312c312d312e312f44782522531422542b2355220823564c4d4b0222382123391c0081e80780046a6f686e2281d00f24231f880003420001892223902291922394239593a0a1a2a3a4a5a6a7a8a9aaabacadae23af3a00003b003c003d8164",
-	5: "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",
+	5: "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}",
 }
 
 func pseudoOp(opcode string) bool {
diff --git a/data/transactions/logic/debugger.go b/data/transactions/logic/debugger.go
index c4477473ca..f90e7b3f3e 100644
--- a/data/transactions/logic/debugger.go
+++ b/data/transactions/logic/debugger.go
@@ -98,7 +98,7 @@ func makeDebugState(cx *EvalContext) DebugState {
 		ExecID:      GetProgramID(cx.program),
 		Disassembly: disasm,
 		PCOffset:    dsInfo.pcOffset,
-		GroupIndex:  cx.GroupIndex,
+		GroupIndex:  int(cx.GroupIndex),
 		TxnGroup:    cx.TxnGroup,
 		Proto:       cx.Proto,
 	}
diff --git a/data/transactions/logic/doc.go b/data/transactions/logic/doc.go
index 760c6a75c0..f921c70ded 100644
--- a/data/transactions/logic/doc.go
+++ b/data/transactions/logic/doc.go
@@ -87,7 +87,9 @@ var opDocByName = map[string]string{
 	"gtxnsa":        "push Ith value of the array field F from the Xth transaction in the current group",
 	"global":        "push value from globals to stack",
 	"load":          "copy a value from scratch space to the stack",
-	"store":         "pop a value from the stack and store to scratch space",
+	"store":         "pop value X. store X to the Ith scratch space",
+	"loads":         "copy a value from the Xth scratch space to the stack",
+	"stores":        "pop indexes A and B. store A to the Bth scratch space",
 	"gload":         "push Ith scratch space index of the Tth transaction in the current group",
 	"gloads":        "push Ith scratch space index of the Xth transaction in the current group",
 	"gaid":          "push the ID of the asset or application created in the Tth transaction of the current group",
@@ -264,7 +266,7 @@ var OpGroups = map[string][]string{
 	"Byte Array Slicing":    {"substring", "substring3", "extract", "extract3", "extract16bits", "extract32bits", "extract64bits"},
 	"Byte Array Arithmetic": {"b+", "b-", "b/", "b*", "b<", "b>", "b<=", "b>=", "b==", "b!=", "b%"},
 	"Byte Array Logic":      {"b|", "b&", "b^", "b~"},
-	"Loading Values":        {"intcblock", "intc", "intc_0", "intc_1", "intc_2", "intc_3", "pushint", "bytecblock", "bytec", "bytec_0", "bytec_1", "bytec_2", "bytec_3", "pushbytes", "bzero", "arg", "arg_0", "arg_1", "arg_2", "arg_3", "txn", "gtxn", "txna", "gtxna", "gtxns", "gtxnsa", "global", "load", "store", "gload", "gloads", "gaid", "gaids", "txnas", "gtxnas", "gtxnsas", "args"},
+	"Loading Values":        {"intcblock", "intc", "intc_0", "intc_1", "intc_2", "intc_3", "pushint", "bytecblock", "bytec", "bytec_0", "bytec_1", "bytec_2", "bytec_3", "pushbytes", "bzero", "arg", "arg_0", "arg_1", "arg_2", "arg_3", "txn", "gtxn", "txna", "txnas", "gtxna", "gtxnas", "gtxns", "gtxnsa", "gtxnsas", "global", "load", "loads", "store", "stores", "gload", "gloads", "gaid", "gaids", "args"},
 	"Flow Control":          {"err", "bnz", "bz", "b", "return", "pop", "dup", "dup2", "dig", "cover", "uncover", "swap", "select", "assert", "callsub", "retsub"},
 	"State Access":          {"balance", "min_balance", "app_opted_in", "app_local_get", "app_local_get_ex", "app_global_get", "app_global_get_ex", "app_local_put", "app_global_put", "app_local_del", "app_global_del", "asset_holding_get", "asset_params_get", "app_params_get", "log"},
 	"Inner Transactions":    {"tx_begin", "tx_field", "tx_submit"},
diff --git a/data/transactions/logic/eval.go b/data/transactions/logic/eval.go
index 507c13e719..bea52b2c98 100644
--- a/data/transactions/logic/eval.go
+++ b/data/transactions/logic/eval.go
@@ -221,7 +221,7 @@ type EvalParams struct {
 	TxnGroup []transactions.SignedTxn
 
 	// GroupIndex should point to Txn within TxnGroup
-	GroupIndex int
+	GroupIndex uint64
 
 	PastSideEffects []EvalSideEffects
 
@@ -342,7 +342,7 @@ type EvalContext struct {
 	instructionStarts map[int]bool
 
 	programHashCached crypto.Digest
-	txidCache         map[int]transactions.Txid
+	txidCache         map[uint64]transactions.Txid
 	appAddrCache      map[basics.AppIndex]basics.Address
 
 	// Stores state & disassembly for the optional debugger
@@ -1854,15 +1854,18 @@ func (cx *EvalContext) appParamsToValue(params *basics.AppParams, fs appParamsFi
 
 // TxnFieldToTealValue is a thin wrapper for txnFieldToStack for external use
 func TxnFieldToTealValue(txn *transactions.Transaction, groupIndex int, field TxnField, arrayFieldIdx uint64) (basics.TealValue, error) {
-	cx := EvalContext{EvalParams: EvalParams{GroupIndex: groupIndex}}
-	sv, err := cx.txnFieldToStack(txn, field, arrayFieldIdx, groupIndex)
+	if groupIndex < 0 {
+		return basics.TealValue{}, fmt.Errorf("negative groupIndex %d", groupIndex)
+	}
+	cx := EvalContext{EvalParams: EvalParams{GroupIndex: uint64(groupIndex)}}
+	sv, err := cx.txnFieldToStack(txn, field, arrayFieldIdx, uint64(groupIndex))
 	return sv.toTealValue(), err
 }
 
-func (cx *EvalContext) getTxID(txn *transactions.Transaction, groupIndex int) transactions.Txid {
+func (cx *EvalContext) getTxID(txn *transactions.Transaction, groupIndex uint64) transactions.Txid {
 	// Initialize txidCache if necessary
 	if cx.txidCache == nil {
-		cx.txidCache = make(map[int]transactions.Txid, len(cx.TxnGroup))
+		cx.txidCache = make(map[uint64]transactions.Txid, len(cx.TxnGroup))
 	}
 
 	// Hashes are expensive, so we cache computed TxIDs
@@ -1875,7 +1878,7 @@ func (cx *EvalContext) getTxID(txn *transactions.Transaction, groupIndex int) tr
 	return txid
 }
 
-func (cx *EvalContext) txnFieldToStack(txn *transactions.Transaction, field TxnField, arrayFieldIdx uint64, groupIndex int) (sv stackValue, err error) {
+func (cx *EvalContext) txnFieldToStack(txn *transactions.Transaction, field TxnField, arrayFieldIdx uint64, groupIndex uint64) (sv stackValue, err error) {
 	err = nil
 	switch field {
 	case Sender:
@@ -1921,7 +1924,7 @@ func (cx *EvalContext) txnFieldToStack(txn *transactions.Transaction, field TxnF
 	case AssetCloseTo:
 		sv.Bytes = txn.AssetCloseTo[:]
 	case GroupIndex:
-		sv.Uint = uint64(groupIndex)
+		sv.Uint = groupIndex
 	case TxID:
 		txid := cx.getTxID(txn, groupIndex)
 		sv.Bytes = txid[:]
@@ -2060,7 +2063,7 @@ func opTxn(cx *EvalContext) {
 }
 
 func opTxna(cx *EvalContext) {
-	field := TxnField(uint64(cx.program[cx.pc+1]))
+	field := TxnField(cx.program[cx.pc+1])
 	fs, ok := txnFieldSpecByField[field]
 	if !ok || fs.version > cx.version {
 		cx.err = fmt.Errorf("invalid txn field %d", field)
@@ -2104,13 +2107,13 @@ func opTxnas(cx *EvalContext) {
 }
 
 func opGtxn(cx *EvalContext) {
-	gtxid := int(uint(cx.program[cx.pc+1]))
-	if gtxid >= len(cx.TxnGroup) {
+	gtxid := cx.program[cx.pc+1]
+	if int(gtxid) >= len(cx.TxnGroup) {
 		cx.err = fmt.Errorf("gtxn lookup TxnGroup[%d] but it only has %d", gtxid, len(cx.TxnGroup))
 		return
 	}
 	tx := &cx.TxnGroup[gtxid].Txn
-	field := TxnField(uint64(cx.program[cx.pc+2]))
+	field := TxnField(cx.program[cx.pc+2])
 	fs, ok := txnFieldSpecByField[field]
 	if !ok || fs.version > cx.version {
 		cx.err = fmt.Errorf("invalid txn field %d", field)
@@ -2127,7 +2130,7 @@ func opGtxn(cx *EvalContext) {
 		// GroupIndex; asking this when we just specified it is _dumb_, but oh well
 		sv.Uint = uint64(gtxid)
 	} else {
-		sv, err = cx.txnFieldToStack(tx, field, 0, gtxid)
+		sv, err = cx.txnFieldToStack(tx, field, 0, uint64(gtxid))
 		if err != nil {
 			cx.err = err
 			return
@@ -2155,7 +2158,7 @@ func opGtxna(cx *EvalContext) {
 		return
 	}
 	arrayFieldIdx := uint64(cx.program[cx.pc+3])
-	sv, err := cx.txnFieldToStack(tx, field, arrayFieldIdx, gtxid)
+	sv, err := cx.txnFieldToStack(tx, field, arrayFieldIdx, uint64(gtxid))
 	if err != nil {
 		cx.err = err
 		return
@@ -2166,13 +2169,10 @@ func opGtxna(cx *EvalContext) {
 func opGtxnas(cx *EvalContext) {
 	last := len(cx.stack) - 1
 
-	gtxid := int(cx.program[cx.pc+1])
-	if gtxid >= len(cx.TxnGroup) {
+	gtxid := cx.program[cx.pc+1]
+	if int(gtxid) >= len(cx.TxnGroup) {
 		cx.err = fmt.Errorf("gtxnas lookup TxnGroup[%d] but it only has %d", gtxid, len(cx.TxnGroup))
 		return
-	} else if gtxid < 0 {
-		cx.err = fmt.Errorf("gtxnas lookup %d cannot be negative", gtxid)
-		return
 	}
 	tx := &cx.TxnGroup[gtxid].Txn
 	field := TxnField(cx.program[cx.pc+2])
@@ -2187,7 +2187,7 @@ func opGtxnas(cx *EvalContext) {
 		return
 	}
 	arrayFieldIdx := cx.stack[last].Uint
-	sv, err := cx.txnFieldToStack(tx, field, arrayFieldIdx, gtxid)
+	sv, err := cx.txnFieldToStack(tx, field, arrayFieldIdx, uint64(gtxid))
 	if err != nil {
 		cx.err = err
 		return
@@ -2197,13 +2197,13 @@ func opGtxnas(cx *EvalContext) {
 
 func opGtxns(cx *EvalContext) {
 	last := len(cx.stack) - 1
-	gtxid := int(cx.stack[last].Uint)
-	if gtxid >= len(cx.TxnGroup) {
+	gtxid := cx.stack[last].Uint
+	if gtxid >= uint64(len(cx.TxnGroup)) {
 		cx.err = fmt.Errorf("gtxns lookup TxnGroup[%d] but it only has %d", gtxid, len(cx.TxnGroup))
 		return
 	}
 	tx := &cx.TxnGroup[gtxid].Txn
-	field := TxnField(uint64(cx.program[cx.pc+1]))
+	field := TxnField(cx.program[cx.pc+1])
 	fs, ok := txnFieldSpecByField[field]
 	if !ok || fs.version > cx.version {
 		cx.err = fmt.Errorf("invalid txn field %d", field)
@@ -2216,9 +2216,9 @@ func opGtxns(cx *EvalContext) {
 	}
 	var sv stackValue
 	var err error
-	if TxnField(field) == GroupIndex {
+	if field == GroupIndex {
 		// GroupIndex; asking this when we just specified it is _dumb_, but oh well
-		sv.Uint = uint64(gtxid)
+		sv.Uint = gtxid
 	} else {
 		sv, err = cx.txnFieldToStack(tx, field, 0, gtxid)
 		if err != nil {
@@ -2231,13 +2231,13 @@ func opGtxns(cx *EvalContext) {
 
 func opGtxnsa(cx *EvalContext) {
 	last := len(cx.stack) - 1
-	gtxid := int(cx.stack[last].Uint)
-	if gtxid >= len(cx.TxnGroup) {
+	gtxid := cx.stack[last].Uint
+	if gtxid >= uint64(len(cx.TxnGroup)) {
 		cx.err = fmt.Errorf("gtxnsa lookup TxnGroup[%d] but it only has %d", gtxid, len(cx.TxnGroup))
 		return
 	}
 	tx := &cx.TxnGroup[gtxid].Txn
-	field := TxnField(uint64(cx.program[cx.pc+1]))
+	field := TxnField(cx.program[cx.pc+1])
 	fs, ok := txnFieldSpecByField[field]
 	if !ok || fs.version > cx.version {
 		cx.err = fmt.Errorf("invalid txn field %d", field)
@@ -2261,13 +2261,10 @@ func opGtxnsas(cx *EvalContext) {
 	last := len(cx.stack) - 1
 	prev := last - 1
 
-	gtxid := int(cx.stack[prev].Uint)
-	if gtxid >= len(cx.TxnGroup) {
+	gtxid := cx.stack[prev].Uint
+	if gtxid >= uint64(len(cx.TxnGroup)) {
 		cx.err = fmt.Errorf("gtxnsas lookup TxnGroup[%d] but it only has %d", gtxid, len(cx.TxnGroup))
 		return
-	} else if gtxid < 0 {
-		cx.err = fmt.Errorf("gtxnsas lookup %d cannot be negative", gtxid)
-		return
 	}
 	tx := &cx.TxnGroup[gtxid].Txn
 	field := TxnField(cx.program[cx.pc+1])
@@ -2291,8 +2288,8 @@ func opGtxnsas(cx *EvalContext) {
 	cx.stack = cx.stack[:last]
 }
 
-func opGaidImpl(cx *EvalContext, groupIdx int, opName string) (sv stackValue, err error) {
-	if groupIdx >= len(cx.TxnGroup) {
+func opGaidImpl(cx *EvalContext, groupIdx uint64, opName string) (sv stackValue, err error) {
+	if groupIdx >= uint64(len(cx.TxnGroup)) {
 		err = fmt.Errorf("%s lookup TxnGroup[%d] but it only has %d", opName, groupIdx, len(cx.TxnGroup))
 		return
 	} else if groupIdx > cx.GroupIndex {
@@ -2319,8 +2316,8 @@ func opGaidImpl(cx *EvalContext, groupIdx int, opName string) (sv stackValue, er
 }
 
 func opGaid(cx *EvalContext) {
-	groupIdx := int(uint(cx.program[cx.pc+1]))
-	sv, err := opGaidImpl(cx, groupIdx, "gaid")
+	groupIdx := cx.program[cx.pc+1]
+	sv, err := opGaidImpl(cx, uint64(groupIdx), "gaid")
 	if err != nil {
 		cx.err = err
 		return
@@ -2331,7 +2328,7 @@ func opGaid(cx *EvalContext) {
 
 func opGaids(cx *EvalContext) {
 	last := len(cx.stack) - 1
-	groupIdx := int(cx.stack[last].Uint)
+	groupIdx := cx.stack[last].Uint
 	sv, err := opGaidImpl(cx, groupIdx, "gaids")
 	if err != nil {
 		cx.err = err
@@ -2390,12 +2387,16 @@ func (cx *EvalContext) getApplicationAddress() (basics.Address, error) {
 	return appAddr, nil
 }
 
-func (cx *EvalContext) getCreatableID(groupIndex int) (cid uint64, err error) {
+func (cx *EvalContext) getCreatableID(groupIndex uint64) (cid uint64, err error) {
 	if cx.Ledger == nil {
 		err = fmt.Errorf("ledger not available")
 		return
 	}
-	return uint64(cx.Ledger.GetCreatableID(groupIndex)), nil
+	gi := int(groupIndex)
+	if gi < 0 {
+		return 0, fmt.Errorf("groupIndex %d too high", groupIndex)
+	}
+	return uint64(cx.Ledger.GetCreatableID(gi)), nil
 }
 
 func (cx *EvalContext) getCreatorAddress() ([]byte, error) {
@@ -2526,22 +2527,44 @@ func opEd25519verify(cx *EvalContext) {
 }
 
 func opLoad(cx *EvalContext) {
-	gindex := int(uint(cx.program[cx.pc+1]))
-	cx.stack = append(cx.stack, cx.scratch[gindex])
+	n := cx.program[cx.pc+1]
+	cx.stack = append(cx.stack, cx.scratch[n])
+}
+
+func opLoads(cx *EvalContext) {
+	last := len(cx.stack) - 1
+	n := cx.stack[last].Uint
+	if n >= uint64(len(cx.scratch)) {
+		cx.err = fmt.Errorf("invalid Scratch index %d", n)
+		return
+	}
+	cx.stack[last] = cx.scratch[n]
 }
 
 func opStore(cx *EvalContext) {
-	gindex := int(uint(cx.program[cx.pc+1]))
+	n := cx.program[cx.pc+1]
 	last := len(cx.stack) - 1
-	cx.scratch[gindex] = cx.stack[last]
+	cx.scratch[n] = cx.stack[last]
 	cx.stack = cx.stack[:last]
 }
 
-func opGloadImpl(cx *EvalContext, groupIdx int, scratchIdx int, opName string) (scratchValue stackValue, err error) {
-	if groupIdx >= len(cx.TxnGroup) {
+func opStores(cx *EvalContext) {
+	last := len(cx.stack) - 1
+	prev := last - 1
+	n := cx.stack[last].Uint
+	if n >= uint64(len(cx.scratch)) {
+		cx.err = fmt.Errorf("invalid Scratch index %d", n)
+		return
+	}
+	cx.scratch[n] = cx.stack[prev]
+	cx.stack = cx.stack[:prev]
+}
+
+func opGloadImpl(cx *EvalContext, groupIdx uint64, scratchIdx byte, opName string) (scratchValue stackValue, err error) {
+	if groupIdx >= uint64(len(cx.TxnGroup)) {
 		err = fmt.Errorf("%s lookup TxnGroup[%d] but it only has %d", opName, groupIdx, len(cx.TxnGroup))
 		return
-	} else if scratchIdx >= 256 {
+	} else if int(scratchIdx) >= len(cx.scratch) {
 		err = fmt.Errorf("invalid Scratch index %d", scratchIdx)
 		return
 	} else if txn := cx.TxnGroup[groupIdx].Txn; txn.Type != protocol.ApplicationCallTx {
@@ -2555,13 +2578,13 @@ func opGloadImpl(cx *EvalContext, groupIdx int, scratchIdx int, opName string) (
 		return
 	}
 
-	scratchValue = cx.PastSideEffects[groupIdx].getScratchValue(uint8(scratchIdx))
+	scratchValue = cx.PastSideEffects[groupIdx].getScratchValue(scratchIdx)
 	return
 }
 
 func opGload(cx *EvalContext) {
-	groupIdx := int(uint(cx.program[cx.pc+1]))
-	scratchIdx := int(uint(cx.program[cx.pc+2]))
+	groupIdx := uint64(cx.program[cx.pc+1])
+	scratchIdx := cx.program[cx.pc+2]
 	scratchValue, err := opGloadImpl(cx, groupIdx, scratchIdx, "gload")
 	if err != nil {
 		cx.err = err
@@ -2573,8 +2596,8 @@ func opGload(cx *EvalContext) {
 
 func opGloads(cx *EvalContext) {
 	last := len(cx.stack) - 1
-	groupIdx := int(cx.stack[last].Uint)
-	scratchIdx := int(uint(cx.program[cx.pc+1]))
+	groupIdx := cx.stack[last].Uint
+	scratchIdx := cx.program[cx.pc+1]
 	scratchValue, err := opGloadImpl(cx, groupIdx, scratchIdx, "gloads")
 	if err != nil {
 		cx.err = err
diff --git a/data/transactions/logic/eval_test.go b/data/transactions/logic/eval_test.go
index 9c9b4edbfd..0993c7c44d 100644
--- a/data/transactions/logic/eval_test.go
+++ b/data/transactions/logic/eval_test.go
@@ -905,7 +905,7 @@ func TestArg(t *testing.T) {
 		t.Run(fmt.Sprintf("v=%d", v), func(t *testing.T) {
 			source := "arg 0; arg 1; ==; arg 2; arg 3; !=; &&; arg 4; len; int 9; <; &&;"
 			if v >= 5 {
-				source += "int 0; args; int 1; args; ==; assert;"
+				source += "int 0; args; int 1; args; ==; assert; int 2; args; int 3; args; !=; assert"
 			}
 			ops := testProg(t, source, v)
 			err := Check(ops.Program, defaultEvalParams(nil, nil))
@@ -2338,6 +2338,33 @@ load 1
 &&`, 1)
 }
 
+func TestLoadStoreStack(t *testing.T) {
+	partitiontest.PartitionTest(t)
+
+	t.Parallel()
+	testAccepts(t, `int 37
+int 37
+int 1
+stores
+byte 0xabbacafe
+int 42
+stores
+int 37
+==
+int 0
+stores
+int 42
+loads
+byte 0xabbacafe
+==
+int 0
+loads
+int 1
+loads
++
+&&`, 5)
+}
+
 func TestLoadStore2(t *testing.T) {
 	partitiontest.PartitionTest(t)
 
@@ -2462,7 +2489,7 @@ int 1`,
 					Proto:           &proto,
 					Txn:             &txgroup[j],
 					TxnGroup:        txgroup,
-					GroupIndex:      j,
+					GroupIndex:      uint64(j),
 					PastSideEffects: pastSideEffects,
 				}
 			}
@@ -2536,7 +2563,7 @@ int 1`,
 					Proto:           &proto,
 					Txn:             &txgroup[j],
 					TxnGroup:        txgroup,
-					GroupIndex:      j,
+					GroupIndex:      uint64(j),
 					PastSideEffects: pastSideEffects,
 				}
 			}
@@ -2609,7 +2636,7 @@ byte "txn 2"
 			Proto:           &proto,
 			Txn:             &txgroup[j],
 			TxnGroup:        txgroup,
-			GroupIndex:      j,
+			GroupIndex:      uint64(j),
 			PastSideEffects: pastSideEffects,
 		}
 	}
diff --git a/data/transactions/logic/opcodes.go b/data/transactions/logic/opcodes.go
index acab24cfa9..a1eec0cd11 100644
--- a/data/transactions/logic/opcodes.go
+++ b/data/transactions/logic/opcodes.go
@@ -206,6 +206,10 @@ var OpSpecs = []OpSpec{
 	{0x3c, "gaid", opGaid, asmDefault, disDefault, nil, oneInt, 4, runModeApplication, immediates("t")},
 	{0x3d, "gaids", opGaids, asmDefault, disDefault, oneInt, oneInt, 4, runModeApplication, opDefault},
 
+	// Like load/store, but scratch slot taken from TOS instead of immediate
+	{0x3e, "loads", opLoads, asmDefault, disDefault, oneInt, oneAny, 5, modeAny, opDefault},
+	{0x3f, "stores", opStores, asmDefault, disDefault, oneAny.plus(oneInt), nil, 5, modeAny, opDefault},
+
 	{0x40, "bnz", opBnz, assembleBranch, disBranch, oneInt, nil, 1, modeAny, opBranch},
 	{0x41, "bz", opBz, assembleBranch, disBranch, oneInt, nil, 2, modeAny, opBranch},
 	{0x42, "b", opB, assembleBranch, disBranch, nil, nil, 2, modeAny, opBranch},
diff --git a/data/transactions/verify/txn.go b/data/transactions/verify/txn.go
index 4e710610dc..671b9a347c 100644
--- a/data/transactions/verify/txn.go
+++ b/data/transactions/verify/txn.go
@@ -286,11 +286,14 @@ func LogicSigSanityCheckBatchVerify(txn *transactions.SignedTxn, groupIndex int,
 		return errors.New("LogicSig.Logic too long")
 	}
 
+	if groupIndex < 0 {
+		return errors.New("Negative groupIndex")
+	}
 	ep := logic.EvalParams{
 		Txn:            txn,
 		Proto:          &groupCtx.consensusParams,
 		TxnGroup:       groupCtx.signedGroupTxns,
-		GroupIndex:     groupIndex,
+		GroupIndex:     uint64(groupIndex),
 		MinTealVersion: &groupCtx.minTealVersion,
 	}
 	err := logic.Check(lsig.Logic, ep)
@@ -340,11 +343,14 @@ func logicSigBatchVerify(txn *transactions.SignedTxn, groupIndex int, groupCtx *
 		return err
 	}
 
+	if groupIndex < 0 {
+		return errors.New("Negative groupIndex")
+	}
 	ep := logic.EvalParams{
 		Txn:            txn,
 		Proto:          &groupCtx.consensusParams,
 		TxnGroup:       groupCtx.signedGroupTxns,
-		GroupIndex:     groupIndex,
+		GroupIndex:     uint64(groupIndex),
 		MinTealVersion: &groupCtx.minTealVersion,
 	}
 	pass, err := logic.Eval(txn.Lsig.Logic, ep)
diff --git a/ledger/eval.go b/ledger/eval.go
index 15c0d04871..20b5a3cd32 100644
--- a/ledger/eval.go
+++ b/ledger/eval.go
@@ -705,7 +705,7 @@ func (eval *BlockEvaluator) prepareEvalParams(txgroup []transactions.SignedTxnWi
 			Txn:                     &groupNoAD[i],
 			Proto:                   &eval.proto,
 			TxnGroup:                groupNoAD,
-			GroupIndex:              i,
+			GroupIndex:              uint64(i),
 			PastSideEffects:         pastSideEffects,
 			MinTealVersion:          &minTealVersion,
 			PooledApplicationBudget: &pooledApplicationBudget,
diff --git a/ledger/eval_test.go b/ledger/eval_test.go
index b0dc43881a..cdaf600bdb 100644
--- a/ledger/eval_test.go
+++ b/ledger/eval_test.go
@@ -418,7 +418,7 @@ func TestPrepareEvalParams(t *testing.T) {
 					if present {
 						require.NotNil(t, res[k])
 						require.NotNil(t, res[k].PastSideEffects)
-						require.Equal(t, res[k].GroupIndex, k)
+						require.Equal(t, res[k].GroupIndex, uint64(k))
 						require.Equal(t, res[k].TxnGroup, expGroupNoAD)
 						require.Equal(t, *res[k].Proto, eval.proto)
 						require.Equal(t, *res[k].Txn, testCase.group[k].SignedTxn)

From fa7c14466656146d16d2e6df17fd70b425a2ddd7 Mon Sep 17 00:00:00 2001
From: John Jannotti <jj@cs.brown.edu>
Date: Wed, 8 Sep 2021 14:49:59 -0400
Subject: [PATCH 2/4] Swap order of stores args

---
 data/transactions/logic/doc.go       | 2 +-
 data/transactions/logic/eval.go      | 4 ++--
 data/transactions/logic/eval_test.go | 9 +++++++--
 data/transactions/logic/opcodes.go   | 2 +-
 4 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/data/transactions/logic/doc.go b/data/transactions/logic/doc.go
index f921c70ded..e339a3f2c6 100644
--- a/data/transactions/logic/doc.go
+++ b/data/transactions/logic/doc.go
@@ -89,7 +89,7 @@ var opDocByName = map[string]string{
 	"load":          "copy a value from scratch space to the stack",
 	"store":         "pop value X. store X to the Ith scratch space",
 	"loads":         "copy a value from the Xth scratch space to the stack",
-	"stores":        "pop indexes A and B. store A to the Bth scratch space",
+	"stores":        "pop indexes A and B. store B to the Ath scratch space",
 	"gload":         "push Ith scratch space index of the Tth transaction in the current group",
 	"gloads":        "push Ith scratch space index of the Xth transaction in the current group",
 	"gaid":          "push the ID of the asset or application created in the Tth transaction of the current group",
diff --git a/data/transactions/logic/eval.go b/data/transactions/logic/eval.go
index bea52b2c98..91b281ea57 100644
--- a/data/transactions/logic/eval.go
+++ b/data/transactions/logic/eval.go
@@ -2551,12 +2551,12 @@ func opStore(cx *EvalContext) {
 func opStores(cx *EvalContext) {
 	last := len(cx.stack) - 1
 	prev := last - 1
-	n := cx.stack[last].Uint
+	n := cx.stack[prev].Uint
 	if n >= uint64(len(cx.scratch)) {
 		cx.err = fmt.Errorf("invalid Scratch index %d", n)
 		return
 	}
-	cx.scratch[n] = cx.stack[prev]
+	cx.scratch[n] = cx.stack[last]
 	cx.stack = cx.stack[:prev]
 }
 
diff --git a/data/transactions/logic/eval_test.go b/data/transactions/logic/eval_test.go
index 0993c7c44d..bf5de97b87 100644
--- a/data/transactions/logic/eval_test.go
+++ b/data/transactions/logic/eval_test.go
@@ -2343,15 +2343,16 @@ func TestLoadStoreStack(t *testing.T) {
 
 	t.Parallel()
 	testAccepts(t, `int 37
-int 37
 int 1
+int 37
 stores
-byte 0xabbacafe
 int 42
+byte 0xabbacafe
 stores
 int 37
 ==
 int 0
+swap
 stores
 int 42
 loads
@@ -4348,6 +4349,7 @@ func testEvaluation(t *testing.T, program string, introduced uint64, tester eval
 	var outer error
 	for v := uint64(1); v <= AssemblerMaxVersion; v++ {
 		t.Run(fmt.Sprintf("v=%d", v), func(t *testing.T) {
+			t.Helper()
 			if v < introduced {
 				testProg(t, obfuscate(program), v, expect{0, "...was introduced..."})
 				return
@@ -4389,17 +4391,20 @@ func testEvaluation(t *testing.T, program string, introduced uint64, tester eval
 }
 
 func testAccepts(t *testing.T, program string, introduced uint64) {
+	t.Helper()
 	testEvaluation(t, program, introduced, func(pass bool, err error) bool {
 		return pass && err == nil
 	})
 }
 func testRejects(t *testing.T, program string, introduced uint64) {
+	t.Helper()
 	testEvaluation(t, program, introduced, func(pass bool, err error) bool {
 		// Returned False, but didn't panic
 		return !pass && err == nil
 	})
 }
 func testPanics(t *testing.T, program string, introduced uint64) error {
+	t.Helper()
 	return testEvaluation(t, program, introduced, func(pass bool, err error) bool {
 		// TEAL panic! not just reject at exit
 		return !pass && err != nil
diff --git a/data/transactions/logic/opcodes.go b/data/transactions/logic/opcodes.go
index a1eec0cd11..8fff33aa03 100644
--- a/data/transactions/logic/opcodes.go
+++ b/data/transactions/logic/opcodes.go
@@ -208,7 +208,7 @@ var OpSpecs = []OpSpec{
 
 	// Like load/store, but scratch slot taken from TOS instead of immediate
 	{0x3e, "loads", opLoads, asmDefault, disDefault, oneInt, oneAny, 5, modeAny, opDefault},
-	{0x3f, "stores", opStores, asmDefault, disDefault, oneAny.plus(oneInt), nil, 5, modeAny, opDefault},
+	{0x3f, "stores", opStores, asmDefault, disDefault, oneInt.plus(oneAny), nil, 5, modeAny, opDefault},
 
 	{0x40, "bnz", opBnz, assembleBranch, disBranch, oneInt, nil, 1, modeAny, opBranch},
 	{0x41, "bz", opBz, assembleBranch, disBranch, oneInt, nil, 2, modeAny, opBranch},

From b162c42afa661399f31c9a275002f68febe099c3 Mon Sep 17 00:00:00 2001
From: John Jannotti <jj@cs.brown.edu>
Date: Wed, 8 Sep 2021 14:59:29 -0400
Subject: [PATCH 3/4] tiny coverage improvement

---
 data/transactions/logic/eval.go | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/data/transactions/logic/eval.go b/data/transactions/logic/eval.go
index 91b281ea57..410a942473 100644
--- a/data/transactions/logic/eval.go
+++ b/data/transactions/logic/eval.go
@@ -1231,12 +1231,12 @@ func opExpImpl(base uint64, exp uint64) (uint64, error) {
 	if exp == 0 || base == 1 {
 		return 1, nil
 	}
-	// base is now at least 2, so exp can not be over 64
-	if exp > 64 {
+	// base is now at least 2, so exp can not be 64
+	if exp >= 64 {
 		return 0, fmt.Errorf("%d^%d overflow", base, exp)
 	}
 	answer := base
-	// safe to cast exp, because it is known to fit in int (it's <= 64)
+	// safe to cast exp, because it is known to fit in int (it's < 64)
 	for i := 1; i < int(exp); i++ {
 		next := answer * base
 		if next/answer != base {
@@ -1274,14 +1274,14 @@ func opExpwImpl(base uint64, exp uint64) (*big.Int, error) {
 	if exp == 0 || base == 1 {
 		return new(big.Int).SetUint64(1), nil
 	}
-	// base is now at least 2, so exp can not be over 128
-	if exp > 128 {
+	// base is now at least 2, so exp can not be 128
+	if exp >= 128 {
 		return &big.Int{}, fmt.Errorf("%d^%d overflow", base, exp)
 	}
 
 	answer := new(big.Int).SetUint64(base)
 	bigbase := new(big.Int).SetUint64(base)
-	// safe to cast exp, because it is known to fit in int (it's <= 128)
+	// safe to cast exp, because it is known to fit in int (it's < 128)
 	for i := 1; i < int(exp); i++ {
 		next := answer.Mul(answer, bigbase)
 		answer = next

From 52d6c86cb79bf79e5872d870c4eb69b61c991864 Mon Sep 17 00:00:00 2001
From: John Jannotti <jj@cs.brown.edu>
Date: Wed, 8 Sep 2021 16:22:45 -0400
Subject: [PATCH 4/4] Generate spec

---
 data/transactions/logic/README.md       | 2 +-
 data/transactions/logic/TEAL_opcodes.md | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/data/transactions/logic/README.md b/data/transactions/logic/README.md
index 098641b385..8af04b0b44 100644
--- a/data/transactions/logic/README.md
+++ b/data/transactions/logic/README.md
@@ -243,7 +243,7 @@ Some of these have immediate data in the byte or bytes after the opcode.
 | `load i` | copy a value from scratch space to the stack |
 | `loads` | copy a value from the Xth scratch space to the stack |
 | `store i` | pop value X. store X to the Ith scratch space |
-| `stores` | pop indexes A and B. store A to the Bth scratch space |
+| `stores` | pop indexes A and B. store B to the Ath scratch space |
 | `gload t i` | push Ith scratch space index of the Tth transaction in the current group |
 | `gloads i` | push Ith scratch space index of the Xth transaction in the current group |
 | `gaid t` | push the ID of the asset or application created in the Tth transaction of the current group |
diff --git a/data/transactions/logic/TEAL_opcodes.md b/data/transactions/logic/TEAL_opcodes.md
index 8bc1dbc0a3..8e60809037 100644
--- a/data/transactions/logic/TEAL_opcodes.md
+++ b/data/transactions/logic/TEAL_opcodes.md
@@ -580,9 +580,9 @@ for notes on transaction fields available, see `txn`. If top of stack is _i_, `g
 ## stores
 
 - Opcode: 0x3f
-- Pops: *... stack*, {any A}, {uint64 B}
+- Pops: *... stack*, {uint64 A}, {any B}
 - Pushes: _None_
-- pop indexes A and B. store A to the Bth scratch space
+- pop indexes A and B. store B to the Ath scratch space
 - LogicSigVersion >= 5
 
 ## bnz target