[MLIR][Affine] Make isValidLoopInterchangePermutation efficient

[arnab-polymage]

Avoid doing dependency checks for the trivial case when size of loops is 1.

[llvmbot]

@llvm/pr-subscribers-mlir

@llvm/pr-subscribers-mlir-affine

Author: Arnab Dutta (arnab-polymage)

Changes

Avoid doing dependency checks for the trivial case when size of loops is 1.

---

Full diff: https://github.com/llvm/llvm-project/pull/128863.diff

1 Files Affected:

• (modified) mlir/lib/Dialect/Affine/Utils/LoopUtils.cpp (+4-2)

diff --git a/mlir/lib/Dialect/Affine/Utils/LoopUtils.cpp b/mlir/lib/Dialect/Affine/Utils/LoopUtils.cpp
index 82b96e9876a6f..6833d6583c27a 100644
--- a/mlir/lib/Dialect/Affine/Utils/LoopUtils.cpp
+++ b/mlir/lib/Dialect/Affine/Utils/LoopUtils.cpp
@@ -1351,10 +1351,12 @@ static bool checkLoopInterchangeDependences(
 /// nested sequence of loops in 'loops' would violate dependences.
 bool mlir::affine::isValidLoopInterchangePermutation(
     ArrayRef<AffineForOp> loops, ArrayRef<unsigned> loopPermMap) {
+  assert(loopPermMap.size() == loops.size() && "invalid loop perm map");
+  unsigned maxLoopDepth = loops.size();
+  if (maxLoopDepth == 1)
+    return true;
   // Gather dependence components for dependences between all ops in loop nest
   // rooted at 'loops[0]', at loop depths in range [1, maxLoopDepth].
-  assert(loopPermMap.size() == loops.size());
-  unsigned maxLoopDepth = loops.size();
   std::vector<SmallVector<DependenceComponent, 2>> depCompsVec;
   getDependenceComponents(loops[0], maxLoopDepth, &depCompsVec);
   return checkLoopInterchangeDependences(depCompsVec, loops, loopPermMap);

[arnab-polymage]

@joker-eph @andydavis1 please review