[MemCpyOpt] Use EarliestEscapeInfo #110280
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Pass EarliestEscapeInfo to BatchAA in MemCpyOpt. This allows memcpy elimination in cases where one of the involved pointers is captured after the relevant memcpy/call.
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@llvm/pr-subscribers-llvm-transforms Author: Nikita Popov (nikic) ChangesPass EarliestEscapeInfo to BatchAA in MemCpyOpt. This allows memcpy elimination in cases where one of the involved pointers is captured after the relevant memcpy/call. Full diff: https://github.com/llvm/llvm-project/pull/110280.diff 3 Files Affected:
diff --git a/llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h b/llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h
index 8ed03d7f3ddbff..e5f78ac2286833 100644
--- a/llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h
+++ b/llvm/include/llvm/Transforms/Scalar/MemCpyOptimizer.h
@@ -26,6 +26,7 @@ class AssumptionCache;
class CallBase;
class CallInst;
class DominatorTree;
+class EarliestEscapeInfo;
class Function;
class Instruction;
class LoadInst;
@@ -48,6 +49,7 @@ class MemCpyOptPass : public PassInfoMixin<MemCpyOptPass> {
PostDominatorTree *PDT = nullptr;
MemorySSA *MSSA = nullptr;
MemorySSAUpdater *MSSAU = nullptr;
+ EarliestEscapeInfo *EEI = nullptr;
public:
MemCpyOptPass() = default;
diff --git a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index e9f212fb482c39..5f7dac14c1deeb 100644
--- a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -284,6 +284,7 @@ static bool mayBeVisibleThroughUnwinding(Value *V, Instruction *Start,
void MemCpyOptPass::eraseInstruction(Instruction *I) {
MSSAU->removeMemoryAccess(I);
+ EEI->removeInstruction(I);
I->eraseFromParent();
}
@@ -638,7 +639,7 @@ bool MemCpyOptPass::processStoreOfLoad(StoreInst *SI, LoadInst *LI,
if (!LI->isSimple() || !LI->hasOneUse() || LI->getParent() != SI->getParent())
return false;
- BatchAAResults BAA(*AA);
+ BatchAAResults BAA(*AA, EEI);
auto *T = LI->getType();
// Don't introduce calls to memcpy/memmove intrinsics out of thin air if
// the corresponding libcalls are not available.
@@ -1751,7 +1752,7 @@ bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
return true;
}
- BatchAAResults BAA(*AA);
+ BatchAAResults BAA(*AA, EEI);
// FIXME: Not using getClobberingMemoryAccess() here due to PR54682.
MemoryAccess *AnyClobber = MA->getDefiningAccess();
MemoryLocation DestLoc = MemoryLocation::getForDest(M);
@@ -1876,7 +1877,7 @@ bool MemCpyOptPass::processByValArgument(CallBase &CB, unsigned ArgNo) {
if (!CallAccess)
return false;
MemCpyInst *MDep = nullptr;
- BatchAAResults BAA(*AA);
+ BatchAAResults BAA(*AA, EEI);
MemoryAccess *Clobber = MSSA->getWalker()->getClobberingMemoryAccess(
CallAccess->getDefiningAccess(), Loc, BAA);
if (auto *MD = dyn_cast<MemoryDef>(Clobber))
@@ -1949,7 +1950,7 @@ bool MemCpyOptPass::processByValArgument(CallBase &CB, unsigned ArgNo) {
/// 4. The memcpy src is not modified during the call. (ModRef check shows no
/// Mod.)
bool MemCpyOptPass::processImmutArgument(CallBase &CB, unsigned ArgNo) {
- BatchAAResults BAA(*AA);
+ BatchAAResults BAA(*AA, EEI);
Value *ImmutArg = CB.getArgOperand(ArgNo);
// 1. Ensure passed argument is immutable during call.
@@ -2117,6 +2118,8 @@ bool MemCpyOptPass::runImpl(Function &F, TargetLibraryInfo *TLI_,
MSSA = MSSA_;
MemorySSAUpdater MSSAU_(MSSA_);
MSSAU = &MSSAU_;
+ EarliestEscapeInfo EEI_(*DT);
+ EEI = &EEI_;
while (true) {
if (!iterateOnFunction(F))
diff --git a/llvm/test/Transforms/MemCpyOpt/memcpy.ll b/llvm/test/Transforms/MemCpyOpt/memcpy.ll
index 0114b9c2443582..39b90adc74ef38 100644
--- a/llvm/test/Transforms/MemCpyOpt/memcpy.ll
+++ b/llvm/test/Transforms/MemCpyOpt/memcpy.ll
@@ -837,7 +837,7 @@ define void @memcpy_memcpy_escape_after1(ptr noalias %P, ptr noalias %Q) {
; CHECK-NEXT: [[MEMTMP:%.*]] = alloca [32 x i8], align 16
; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 16 [[MEMTMP]], ptr align 16 [[P:%.*]], i32 32, i1 false)
; CHECK-NEXT: call void @do_something()
-; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 16 [[Q:%.*]], ptr align 16 [[MEMTMP]], i32 32, i1 false)
+; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 16 [[Q:%.*]], ptr align 16 [[P]], i32 32, i1 false)
; CHECK-NEXT: call void @capture(ptr [[MEMTMP]])
; CHECK-NEXT: ret void
;
@@ -851,10 +851,8 @@ define void @memcpy_memcpy_escape_after1(ptr noalias %P, ptr noalias %Q) {
define void @memcpy_memcpy_escape_after2(ptr noalias %P, ptr noalias %Q) {
; CHECK-LABEL: @memcpy_memcpy_escape_after2(
-; CHECK-NEXT: [[MEMTMP:%.*]] = alloca [32 x i8], align 16
-; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 16 [[MEMTMP]], ptr align 16 [[P:%.*]], i32 32, i1 false)
; CHECK-NEXT: call void @do_something()
-; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 16 [[Q:%.*]], ptr align 16 [[MEMTMP]], i32 32, i1 false)
+; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i32(ptr align 16 [[Q:%.*]], ptr align 16 [[P:%.*]], i32 32, i1 false)
; CHECK-NEXT: call void @capture(ptr [[P]])
; CHECK-NEXT: ret void
;
@@ -868,10 +866,8 @@ define void @memcpy_memcpy_escape_after2(ptr noalias %P, ptr noalias %Q) {
define void @memcpy_byval_escape_after(ptr noalias %P) {
; CHECK-LABEL: @memcpy_byval_escape_after(
-; CHECK-NEXT: [[A:%.*]] = alloca [8 x i8], align 1
-; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 4 [[A]], ptr align 4 [[P:%.*]], i64 8, i1 false)
; CHECK-NEXT: call void @do_something()
-; CHECK-NEXT: call void @test4a(ptr byval(i8) align 1 [[A]])
+; CHECK-NEXT: call void @test4a(ptr byval(i8) align 1 [[P:%.*]])
; CHECK-NEXT: call void @capture(ptr [[P]])
; CHECK-NEXT: ret void
;
@@ -885,10 +881,8 @@ define void @memcpy_byval_escape_after(ptr noalias %P) {
define void @memcpy_immut_escape_after(ptr align 4 noalias %val) {
; CHECK-LABEL: @memcpy_immut_escape_after(
-; CHECK-NEXT: [[VAL1:%.*]] = alloca i8, align 4
-; CHECK-NEXT: call void @llvm.memcpy.p0.p0.i64(ptr align 4 [[VAL1]], ptr align 4 [[VAL:%.*]], i64 1, i1 false)
; CHECK-NEXT: call void @do_something()
-; CHECK-NEXT: call void @f(ptr noalias nocapture readonly align 4 [[VAL1]])
+; CHECK-NEXT: call void @f(ptr noalias nocapture readonly align 4 [[VAL:%.*]])
; CHECK-NEXT: call void @capture(ptr [[VAL]])
; CHECK-NEXT: ret void
;
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This was referenced Sep 27, 2024
DianQK
approved these changes
Sep 27, 2024
There was a problem hiding this comment.
LGTM, thanks!
This context is https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm/topic/nocapture.20and.20allocation.20elimination.
dtcxzyw
approved these changes
Sep 28, 2024
| @@ -284,6 +284,7 @@ static bool mayBeVisibleThroughUnwinding(Value *V, Instruction *Start, | |||
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| void MemCpyOptPass::eraseInstruction(Instruction *I) { | |||
| MSSAU->removeMemoryAccess(I); | |||
| EEI->removeInstruction(I); | |||
There was a problem hiding this comment.
Should we call MemCpyOptPass::eraseInstruction in
NewCopySource may be deleted after a BAA query.
nikic
added a commit
to nikic/llvm-project
that referenced
this pull request
Sep 30, 2024
After llvm#110280 we use EarliestEscapeInfo, so callCapturesBefore() is mostly redundant. It can provide better results in some cases because EEI does an approximation across all captures. I hope that it's good enough in practice, as this is the last remaining user of callCapturesBefore(), so we'll be able to remove this API entirely.
xgupta
pushed a commit
to xgupta/llvm-project
that referenced
this pull request
Oct 4, 2024
Pass EarliestEscapeInfo to BatchAA in MemCpyOpt. This allows memcpy elimination in cases where one of the involved pointers is captured after the relevant memcpy/call.
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Pass EarliestEscapeInfo to BatchAA in MemCpyOpt. This allows memcpy elimination in cases where one of the involved pointers is captured after the relevant memcpy/call.