[Mlir-commits] [mlir] [MLIR][SCFToAffine] Validate inlined affine bound operands (PR #217473)

[Mehdi Amini]

https://github.com/joker-eph created https://github.com/llvm/llvm-project/pull/217473

Validate affine.max and affine.min operands before inlining their maps into affine.for bounds. This defers nested loops until enclosing induction variables become valid affine dimensions and keeps the exported pattern independent of greedy traversal order.

Assisted-by: Codex

>From 7a43835415a49caec3e17ed6d25c82d09b183270 Mon Sep 17 00:00:00 2001
From: Mehdi Amini <joker.eph at gmail.com>
Date: Wed, 19 Aug 2026 07:42:43 -0700
Subject: [PATCH] [MLIR][SCFToAffine] Validate inlined affine bound operands

Validate affine.max and affine.min operands before inlining their maps into
affine.for bounds. This defers nested loops until enclosing induction
variables become valid affine dimensions and keeps the exported pattern
independent of greedy traversal order.

Assisted-by: Codex
---
 .../Conversion/SCFToAffine/SCFToAffine.cpp    | 32 +++++++++++++++----
 .../Conversion/SCFToAffine/scf-to-affine.mlir |  2 --
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/mlir/lib/Conversion/SCFToAffine/SCFToAffine.cpp b/mlir/lib/Conversion/SCFToAffine/SCFToAffine.cpp
index 488aae4c714c5..7113fbcd3c0e3 100644
--- a/mlir/lib/Conversion/SCFToAffine/SCFToAffine.cpp
+++ b/mlir/lib/Conversion/SCFToAffine/SCFToAffine.cpp
@@ -102,20 +102,40 @@ struct ForOpRewrite : public OpRewritePattern<scf::ForOp> {
                                  PatternRewriter &rewriter) const;
 };
 
+static bool areValidAffineMapOperands(AffineMap map, ValueRange operands,
+                                      Region *scope) {
+  assert(map.getNumInputs() == operands.size() &&
+         "expected one operand per affine map input");
+  return llvm::all_of(
+             operands.take_front(map.getNumDims()),
+             [&](Value value) { return affine::isValidDim(value, scope); }) &&
+         llvm::all_of(operands.drop_front(map.getNumDims()), [&](Value value) {
+           return affine::isValidSymbol(value, scope);
+         });
+}
+
 bool indexBoundsRaisable(scf::ForOp op) {
   Value lb = op.getLowerBound();
   Value ub = op.getUpperBound();
   IntegerAttr constAttr;
+  Region *scope = affine::getAffineScope(op);
+  if (!scope)
+    return false;
 
   // The asymmetry between lb and ub comes from the fact that the step
   // normalization (for non-constant (dynamic) steps) does not work with
   // multiple *lower* bounds (max).
-  bool lbOK = affine::isValidDim(lb) ||
-              (isa_and_present<affine::AffineMaxOp>(lb.getDefiningOp()) &&
-               matchPattern(op.getStep(), m_Constant(&constAttr)));
-  bool ubOK = affine::isValidDim(ub) ||
-              isa_and_present<affine::AffineMinOp>(ub.getDefiningOp());
-  bool stepOK = affine::isValidSymbol(op.getStep());
+  auto lbMaxOp = lb.getDefiningOp<affine::AffineMaxOp>();
+  bool lbOK = affine::isValidDim(lb, scope) ||
+              (lbMaxOp && matchPattern(op.getStep(), m_Constant(&constAttr)) &&
+               areValidAffineMapOperands(lbMaxOp.getAffineMap(),
+                                         lbMaxOp->getOperands(), scope));
+  auto ubMinOp = ub.getDefiningOp<affine::AffineMinOp>();
+  bool ubOK =
+      affine::isValidDim(ub, scope) ||
+      (ubMinOp && areValidAffineMapOperands(ubMinOp.getAffineMap(),
+                                            ubMinOp->getOperands(), scope));
+  bool stepOK = affine::isValidSymbol(op.getStep(), scope);
 
   return lbOK && ubOK && stepOK;
 }
diff --git a/mlir/test/Conversion/SCFToAffine/scf-to-affine.mlir b/mlir/test/Conversion/SCFToAffine/scf-to-affine.mlir
index a489e3c3ce9ef..22810df34da27 100644
--- a/mlir/test/Conversion/SCFToAffine/scf-to-affine.mlir
+++ b/mlir/test/Conversion/SCFToAffine/scf-to-affine.mlir
@@ -1,7 +1,5 @@
 // RUN: mlir-opt --raise-scf-to-affine --split-input-file %s | FileCheck %s
 
-// XFAIL: mlir-expensive-checks
-
 // CHECK-LABEL: @constant_step
 // CHECK-SAME:  %[[ARR:.*]]: memref<?xi32>, %[[LB:.*]]: index, %[[UB:.*]]: index
 // CHECK:         affine.for %[[IV:.*]] = %[[LB]] to %[[UB]] step 3 {