[Mlir-commits] [mlir] Fix bug in `visitDivExpr`, `visitModExpr` and `visitMulExpr` (PR #145290)
Arnab Dutta
llvmlistbot at llvm.org
Mon Jun 30 06:02:23 PDT 2025
https://github.com/arnab-polymage updated https://github.com/llvm/llvm-project/pull/145290
>From 781396463e3530854b2858bb4d2647040293dd59 Mon Sep 17 00:00:00 2001
From: Arnab Dutta <arnab at polymagelabs.com>
Date: Mon, 30 Jun 2025 18:31:53 +0530
Subject: [PATCH] Fix bug in `visitDivExpr`, `visitMulExpr` and `visitModExpr`
Whenever the result of a div or mod affine expression is a
constant expression, place the value in the constant index of the
flattened expression instead of adding it as a local expression.
---
mlir/include/mlir/IR/AffineExprVisitor.h | 8 +++++
mlir/lib/IR/AffineExpr.cpp | 35 ++++++++++++++-----
.../Dialect/Affine/simplify-structures.mlir | 29 +++++++++++++++
3 files changed, 64 insertions(+), 8 deletions(-)
diff --git a/mlir/include/mlir/IR/AffineExprVisitor.h b/mlir/include/mlir/IR/AffineExprVisitor.h
index 1826f5fd8ad35..b3c101e4e2f47 100644
--- a/mlir/include/mlir/IR/AffineExprVisitor.h
+++ b/mlir/include/mlir/IR/AffineExprVisitor.h
@@ -418,6 +418,14 @@ class SimpleAffineExprFlattener
AffineExpr localExpr);
private:
+ /// Flatten binary expression `expr` and add it to `result`. If `expr` is a
+ /// dimension, symbol or constant, we add it to appropriate index in `result`.
+ /// Otherwise we add it in the local variable section. `lhs` and `rhs` are the
+ /// LHS and RHS expressions of `expr`.
+ LogicalResult addExprToFlattenedList(AffineExpr expr, ArrayRef<int64_t> lhs,
+ ArrayRef<int64_t> rhs,
+ SmallVectorImpl<int64_t> &result);
+
/// Adds `localExpr`, which may be mod, ceildiv, floordiv or mod expression
/// representing the affine expression corresponding to the quantifier
/// introduced as the local variable corresponding to `localExpr`. If the
diff --git a/mlir/lib/IR/AffineExpr.cpp b/mlir/lib/IR/AffineExpr.cpp
index cc81f9d19aca7..5c262c1179b9c 100644
--- a/mlir/lib/IR/AffineExpr.cpp
+++ b/mlir/lib/IR/AffineExpr.cpp
@@ -1177,10 +1177,9 @@ static AffineExpr getSemiAffineExprFromFlatForm(ArrayRef<int64_t> flatExprs,
if (flatExprs[numDims + numSymbols + it.index()] == 0)
continue;
AffineExpr expr = it.value();
- auto binaryExpr = dyn_cast<AffineBinaryOpExpr>(expr);
- if (!binaryExpr)
- continue;
-
+ // A local expression cannot be a dimension, symbol or a constant -- it
+ // should be a binary op expression.
+ auto binaryExpr = cast<AffineBinaryOpExpr>(expr);
AffineExpr lhs = binaryExpr.getLHS();
AffineExpr rhs = binaryExpr.getRHS();
if (!((isa<AffineDimExpr>(lhs) || isa<AffineSymbolExpr>(lhs)) &&
@@ -1274,6 +1273,27 @@ SimpleAffineExprFlattener::SimpleAffineExprFlattener(unsigned numDims,
operandExprStack.reserve(8);
}
+LogicalResult SimpleAffineExprFlattener::addExprToFlattenedList(
+ AffineExpr expr, ArrayRef<int64_t> lhs, ArrayRef<int64_t> rhs,
+ SmallVectorImpl<int64_t> &result) {
+ if (auto constExpr = dyn_cast<AffineConstantExpr>(expr)) {
+ std::fill(result.begin(), result.end(), 0);
+ result[getConstantIndex()] = constExpr.getValue();
+ return success();
+ }
+ if (auto dimExpr = dyn_cast<AffineDimExpr>(expr)) {
+ std::fill(result.begin(), result.end(), 0);
+ result[getDimStartIndex() + dimExpr.getPosition()] = 1;
+ return success();
+ }
+ if (auto symExpr = dyn_cast<AffineSymbolExpr>(expr)) {
+ std::fill(result.begin(), result.end(), 0);
+ result[getSymbolStartIndex() + symExpr.getPosition()] = 1;
+ return success();
+ }
+ return addLocalVariableSemiAffine(lhs, rhs, expr, result, result.size());
+}
+
// In pure affine t = expr * c, we multiply each coefficient of lhs with c.
//
// In case of semi affine multiplication expressions, t = expr * symbolic_expr,
@@ -1295,7 +1315,7 @@ LogicalResult SimpleAffineExprFlattener::visitMulExpr(AffineBinaryOpExpr expr) {
localExprs, context);
AffineExpr b = getAffineExprFromFlatForm(rhs, numDims, numSymbols,
localExprs, context);
- return addLocalVariableSemiAffine(mulLhs, rhs, a * b, lhs, lhs.size());
+ return addExprToFlattenedList(a * b, mulLhs, rhs, lhs);
}
// Get the RHS constant.
@@ -1347,8 +1367,7 @@ LogicalResult SimpleAffineExprFlattener::visitModExpr(AffineBinaryOpExpr expr) {
lhs, numDims, numSymbols, localExprs, context);
AffineExpr divisorExpr = getAffineExprFromFlatForm(rhs, numDims, numSymbols,
localExprs, context);
- AffineExpr modExpr = dividendExpr % divisorExpr;
- return addLocalVariableSemiAffine(modLhs, rhs, modExpr, lhs, lhs.size());
+ return addExprToFlattenedList(dividendExpr % divisorExpr, modLhs, rhs, lhs);
}
int64_t rhsConst = rhs[getConstantIndex()];
@@ -1482,7 +1501,7 @@ LogicalResult SimpleAffineExprFlattener::visitDivExpr(AffineBinaryOpExpr expr,
AffineExpr b = getAffineExprFromFlatForm(rhs, numDims, numSymbols,
localExprs, context);
AffineExpr divExpr = isCeil ? a.ceilDiv(b) : a.floorDiv(b);
- return addLocalVariableSemiAffine(divLhs, rhs, divExpr, lhs, lhs.size());
+ return addExprToFlattenedList(divExpr, divLhs, rhs, lhs);
}
// This is a pure affine expr; the RHS is a positive constant.
diff --git a/mlir/test/Dialect/Affine/simplify-structures.mlir b/mlir/test/Dialect/Affine/simplify-structures.mlir
index 6f2737a982752..17d4ab4dfe448 100644
--- a/mlir/test/Dialect/Affine/simplify-structures.mlir
+++ b/mlir/test/Dialect/Affine/simplify-structures.mlir
@@ -608,3 +608,32 @@ func.func @semiaffine_simplification_floordiv_and_ceildiv_const(%arg0: tensor<?x
// CHECK-NEXT: return %[[C6]], %[[C7]]
return %a, %b : index, index
}
+
+// -----
+
+// CHECK-DAG: #[[$MAP:.*]] = affine_map<()[s0] -> (13 mod s0)>
+// CHECK-DAG: #[[$MAP1:.*]] = affine_map<(d0) -> (d0 * 2)>
+// CHECK-LABEL: semi_affine_simplification_local_expr_folded_into_non_binary_expr
+func.func @semi_affine_simplification_local_expr_folded_into_non_binary_expr(%arg0: memref<?x?xf32>) -> (index, index) {
+ %c0 = arith.constant 0 : index
+ %c1 = arith.constant 1 : index
+ %c4 = arith.constant 4 : index
+ %c13 = arith.constant 13 : index
+ // CHECK: %[[DIM:.*]] = memref.dim
+ %dim = memref.dim %arg0, %c0 : memref<?x?xf32>
+ // CHECK: %[[VAL0:.*]] = affine.apply #[[$MAP]]()[%[[DIM]]]
+ %c = affine.apply affine_map<()[s0, s1, s2, s3] -> (s0 mod (s1 + (-s1 + s3) * (-s1 + s1 * s2 + 1)))>()[%c13, %dim, %c1, %dim]
+ %alloc = memref.alloc() : memref<1xindex>
+ affine.for %iv = 0 to 1 {
+ %d = affine.apply affine_map<(d0)[s1, s2] -> ((d0 - s1 + s1 * s2) * (s1 + (-s1 + 2) * (-s1 + s1 * s2 + 1)))>(%iv)[%dim, %c1]
+ affine.store %d, %alloc[0] : memref<1xindex>
+ }
+ // CHECK: affine.for %[[IV:.*]] = 0 to 1 {
+ // CHECK-NEXT: %[[VAL:.*]] = affine.apply #[[$MAP1]](%[[IV]])
+ // CHECK-NEXT: affine.store %[[VAL]], %{{.*}}[0] : memref<1xindex>
+ // CHECK-NEXT: }
+ // CHECK: %[[VAL1:.*]] = affine.load %{{.*}}[0]
+ %d = affine.load %alloc[0] : memref<1xindex>
+ // CHECK: return %[[VAL0]], %[[VAL1]]
+ return %c, %d : index, index
+}
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