[mlir][scf] Implement getSingle... of LoopLikeOpInterface for scf::ForallOp

[ubfx]

The getSingle(IterationVar|UpperBound|LowerBound|Step) methods of LoopLikeOpInterface are
useful to quickly query the iteration space of unidimensional loops. Until now,
scf::ForallOp always fell back to the default implementation of these methods,
returning std::nullopt.

This patch implements those methods, returning the respective bounds or steps
in the special case of rank == 1.

[llvmbot]

@llvm/pr-subscribers-mlir-scf

@llvm/pr-subscribers-mlir

Changes

The getSingle(UpperBound|LowerBound|Step) methods of LoopLikeOpInterface are
useful to quickly query the iteration space of unidimensional loops. Until now,
scf::ForallOp always fell back to the default implementation of these methods,
returning std::nullopt.

This patch implements those methods, returning the respective bounds or steps
in the special case of rank == 1.

---

Full diff: https://github.com/llvm/llvm-project/pull/67883.diff

2 Files Affected:

• (modified) mlir/include/mlir/Dialect/SCF/IR/SCFOps.td (+2-1)
• (modified) mlir/lib/Dialect/SCF/IR/SCF.cpp (+21)

diff --git a/mlir/include/mlir/Dialect/SCF/IR/SCFOps.td b/mlir/include/mlir/Dialect/SCF/IR/SCFOps.td
index e1a604a88715f0e..218d3b09d96fb05 100644
--- a/mlir/include/mlir/Dialect/SCF/IR/SCFOps.td
+++ b/mlir/include/mlir/Dialect/SCF/IR/SCFOps.td
@@ -331,7 +331,8 @@ def ForallOp : SCF_Op<"forall", [
        AttrSizedOperandSegments,
        AutomaticAllocationScope,
        DeclareOpInterfaceMethods<LoopLikeOpInterface,
-          ["promoteIfSingleIteration"]>,
+          ["promoteIfSingleIteration", "getSingleLowerBound",
+          "getSingleUpperBound", "getSingleStep"]>,
        RecursiveMemoryEffects,
        SingleBlockImplicitTerminator<"scf::InParallelOp">,
        DeclareOpInterfaceMethods<RegionBranchOpInterface>,
diff --git a/mlir/lib/Dialect/SCF/IR/SCF.cpp b/mlir/lib/Dialect/SCF/IR/SCF.cpp
index 8d8481421e18d57..bfe6ccd7b1169df 100644
--- a/mlir/lib/Dialect/SCF/IR/SCF.cpp
+++ b/mlir/lib/Dialect/SCF/IR/SCF.cpp
@@ -1526,6 +1526,27 @@ InParallelOp ForallOp::getTerminator() {
   return cast<InParallelOp>(getBody()->getTerminator());
 }
 
+std::optional<OpFoldResult> ForallOp::getSingleLowerBound() {
+  if (getRank() != 1)
+    return std::nullopt;
+
+  return getMixedLowerBound()[0];
+}
+
+std::optional<OpFoldResult> ForallOp::getSingleUpperBound() {
+  if (getRank() != 1)
+    return std::nullopt;
+
+  return getMixedUpperBound()[0];
+}
+
+std::optional<OpFoldResult> ForallOp::getSingleStep() {
+  if (getRank() != 1)
+    return std::nullopt;
+
+  return getMixedStep()[0];
+}
+
 ForallOp mlir::scf::getForallOpThreadIndexOwner(Value val) {
   auto tidxArg = llvm::dyn_cast<BlockArgument>(val);
   if (!tidxArg)