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

[Allen zhong via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Allen marked 2 inline comments as done.
Closed by commit rG3e6ba89055c8: [InstCombine] Fold a mul with bool value into and (authored by Allen).

Changed prior to commit:
  https://reviews.llvm.org/D126040?vs=432830&id=432904#toc

Repository:
  rG LLVM Github Monorepo

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
@@ -169,13 +169,31 @@
 ; Scalar tests
 define i64 @scalar_mul_bit_x0_y0(i64 %x, i64 %y) {
 ; CHECK-LABEL: @scalar_mul_bit_x0_y0(
+; CHECK-NEXT:    [[AND2:%.*]] = and i64 [[Y:%.*]], 1
+; CHECK-NEXT:    [[MUL:%.*]] = and i64 [[AND2]], [[X:%.*]]
+; CHECK-NEXT:    ret i64 [[MUL]]
+;
+  %and1 = and i64 %x, 1
+  %and2 = and i64 %y, 1
+  %mul = mul i64 %and1, %and2
+  ret i64 %mul
+}
+
+declare void @use(i64)
+
+define i64 @scalar_mul_bit_x0_y0_uses(i64 %x, i64 %y) {
+; CHECK-LABEL: @scalar_mul_bit_x0_y0_uses(
 ; CHECK-NEXT:    [[AND1:%.*]] = and i64 [[X:%.*]], 1
+; CHECK-NEXT:    call void @use(i64 [[AND1]])
 ; CHECK-NEXT:    [[AND2:%.*]] = and i64 [[Y:%.*]], 1
-; CHECK-NEXT:    [[MUL:%.*]] = mul nuw nsw i64 [[AND1]], [[AND2]]
+; CHECK-NEXT:    call void @use(i64 [[AND2]])
+; CHECK-NEXT:    [[MUL:%.*]] = and i64 [[AND2]], [[X]]
 ; CHECK-NEXT:    ret i64 [[MUL]]
 ;
   %and1 = and i64 %x, 1
+  call void @use(i64 %and1)
   %and2 = and i64 %y, 1
+  call void @use(i64 %and2)
   %mul = mul i64 %and1, %and2
   ret i64 %mul
 }
@@ -210,9 +228,8 @@
 ; 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
@@ -301,9 +301,15 @@
     }
   }
 
-  // i1 mul -> i1 and.
+  // Fold the following two scenarios:
+  //   1) i1 mul -> i1 and.
+  //   2) X * Y --> X & Y, iff X, Y can be only {0,1}.
+  // Note: We could use known bits to generalize this and related patterns with
+  // shifts/truncs
   Type *Ty = I.getType();
-  if (Ty->isIntOrIntVectorTy(1))
+  if (Ty->isIntOrIntVectorTy(1) ||
+      (match(Op0, m_And(m_Value(), m_One())) &&
+       match(Op1, m_And(m_Value(), m_One()))))
     return BinaryOperator::CreateAnd(Op0, Op1);
 
   // X*(1 << Y) --> X << Y


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