[mlir][arith] fix canonicalization of mulsi_extended for i1

[s-khechnev]

There is the MulSIExtendedRHSOne canonicalization for arith.mulsi_extended that is defined as follows: mulsi_extended(x, 1) -> [x, extsi(cmpi slt, x, 0)]. In the implementation of this, there is a IsScalarOrSplatOne constraint for the second argument. However, this constraint does not correctly handle situation when multiplying i1 values. Therefore, an additional constraint has been added which checks the second argument for strict positivity.

fix #88732

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[llvmbot]

@llvm/pr-subscribers-mlir

@llvm/pr-subscribers-mlir-arith

Author: Semyon Khechnev (s-khechnev)

Changes

There is the MulSIExtendedRHSOne canonicalization for arith.mulsi_extended that is defined as follows: mulsi_extended(x, 1) -> [x, extsi(cmpi slt, x, 0)]. In the implementation of this, there is a IsScalarOrSplatOne constraint for the second argument. However, this constraint does not correctly handle situation when multiplying i1 values. The 1:i1 in case of signed multiplication is actually -1. Therefore, an additional constraint has been added which checks the second argument for strict positivity.

fix #88732

---

Full diff: https://github.com/llvm/llvm-project/pull/90150.diff

2 Files Affected:

• (modified) mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td (+1)
• (modified) mlir/test/Dialect/Arith/canonicalize.mlir (+22)

diff --git a/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td b/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
index caca2ff81964f7..02d05780a7ac1d 100644
--- a/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
+++ b/mlir/lib/Dialect/Arith/IR/ArithCanonicalization.td
@@ -175,6 +175,7 @@ def MulSIExtendedToMulI :
 def IsScalarOrSplatOne :
     Constraint<And<[
       CPred<"succeeded(getIntOrSplatIntValue($0))">,
+      CPred<"getIntOrSplatIntValue($0)->isStrictlyPositive()">,
       CPred<"*getIntOrSplatIntValue($0) == 1">]>>;
 
 // mulsi_extended(x, 1) -> [x, extsi(cmpi slt, x, 0)]
diff --git a/mlir/test/Dialect/Arith/canonicalize.mlir b/mlir/test/Dialect/Arith/canonicalize.mlir
index 79a318565e98f9..6c4193bc06ca2d 100644
--- a/mlir/test/Dialect/Arith/canonicalize.mlir
+++ b/mlir/test/Dialect/Arith/canonicalize.mlir
@@ -1223,6 +1223,28 @@ func.func @mulsiExtendedOneRhsSplat(%arg0: vector<3xi32>) -> (vector<3xi32>, vec
   return %low, %high : vector<3xi32>, vector<3xi32>
 }
 
+// CHECK-LABEL: @mulsiExtendedOneRhsI1
+//  CHECK-SAME:   (%[[ARG:.+]]: i1) -> (i1, i1)
+//  CHECK-NEXT:   %[[T:.+]]  = arith.constant true
+//  CHECK-NEXT:   %[[LOW:.+]], %[[HIGH:.+]] = arith.mulsi_extended %[[ARG]], %[[T]] : i1
+//  CHECK-NEXT:   return %[[LOW]], %[[HIGH]] : i1, i1
+func.func @mulsiExtendedOneRhsI1(%arg0: i1) -> (i1, i1) {
+  %one = arith.constant true
+  %low, %high = arith.mulsi_extended %arg0, %one: i1
+  return %low, %high : i1, i1
+}
+
+// CHECK-LABEL: @mulsiExtendedOneRhsSplatI1
+//  CHECK-SAME:   (%[[ARG:.+]]: vector<3xi1>) -> (vector<3xi1>, vector<3xi1>)
+//  CHECK-NEXT:   %[[TS:.+]]  = arith.constant dense<true> : vector<3xi1>
+//  CHECK-NEXT:   %[[LOW:.+]], %[[HIGH:.+]] = arith.mulsi_extended %[[ARG]], %[[TS]] : vector<3xi1>
+//  CHECK-NEXT:   return %[[LOW]], %[[HIGH]] : vector<3xi1>, vector<3xi1>
+func.func @mulsiExtendedOneRhsSplatI1(%arg0: vector<3xi1>) -> (vector<3xi1>, vector<3xi1>) {
+  %one = arith.constant dense<true> : vector<3xi1>
+  %low, %high = arith.mulsi_extended %arg0, %one: vector<3xi1>
+  return %low, %high : vector<3xi1>, vector<3xi1>
+}
+
 // CHECK-LABEL: @mulsiExtendedUnusedHigh
 //  CHECK-SAME:   (%[[ARG:.+]]: i32) -> i32
 //  CHECK-NEXT:   %[[RES:.+]] = arith.muli %[[ARG]], %[[ARG]] : i32

[kuhar]

LGTM. Thanks for fixing this.

[kuhar]

I rebased to retrigger CI -- it seemed like it got stuck.

[s-khechnev]

Thanks @kuhar. I don’t have commit access, can you merge this PR for me?

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