[PATCH] D126040: [InstCombine] Fold a mul with bool value into and

[Allen zhong via Phabricator via llvm-commits]

Allen updated this revision to Diff 431955.
Allen added a comment.

rebase to the top after precommit the test cases


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D126040/new/

https://reviews.llvm.org/D126040

Files:
  llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  llvm/test/Transforms/InstCombine/mul-masked-bits.ll


Index: llvm/test/Transforms/InstCombine/mul-masked-bits.ll
===================================================================
--- llvm/test/Transforms/InstCombine/mul-masked-bits.ll
+++ llvm/test/Transforms/InstCombine/mul-masked-bits.ll
@@ -169,9 +169,8 @@
 ; Scalar tests
 define i64 @scalar_mul_bit_x0_y0(i64 %x, i64 %y) {
 ; CHECK-LABEL: @scalar_mul_bit_x0_y0(
-; CHECK-NEXT:    [[AND1:%.*]] = and i64 [[X:%.*]], 1
 ; CHECK-NEXT:    [[AND2:%.*]] = and i64 [[Y:%.*]], 1
-; CHECK-NEXT:    [[MUL:%.*]] = mul nuw nsw i64 [[AND1]], [[AND2]]
+; CHECK-NEXT:    [[MUL:%.*]] = and i64 [[AND2]], [[X:%.*]]
 ; CHECK-NEXT:    ret i64 [[MUL]]
 ;
   %and1 = and i64 %x, 1
@@ -210,9 +209,8 @@
 ; Vector tests
 define <2 x i64> @vector_mul_bit_x0_y0(<2 x i64> %x, <2 x i64> %y) {
 ; CHECK-LABEL: @vector_mul_bit_x0_y0(
-; CHECK-NEXT:    [[AND1:%.*]] = and <2 x i64> [[X:%.*]], <i64 1, i64 1>
 ; CHECK-NEXT:    [[AND2:%.*]] = and <2 x i64> [[Y:%.*]], <i64 1, i64 1>
-; CHECK-NEXT:    [[MUL:%.*]] = mul nuw nsw <2 x i64> [[AND1]], [[AND2]]
+; CHECK-NEXT:    [[MUL:%.*]] = and <2 x i64> [[AND2]], [[X:%.*]]
 ; CHECK-NEXT:    ret <2 x i64> [[MUL]]
 ;
   %and1 = and <2 x i64> %x, <i64 1, i64 1>
Index: llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -305,6 +305,13 @@
   if (I.getType()->isIntOrIntVectorTy(1))
     return BinaryOperator::CreateAnd(Op0, Op1);
 
+  // X * Y --> X & Y, iff X, Y can be only 1.
+  // Note: We could use known bits to generalize this and related patterns with
+  // shifts/truncs
+  if (match(Op0, m_And(m_Value(X), m_One())) &&
+      match(Op1, m_And(m_Value(Y), m_One())))
+    return BinaryOperator::CreateAnd(Op0, Op1);
+
   // X*(1 << Y) --> X << Y
   // (1 << Y)*X --> X << Y
   {


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