[llvm] 40fcc42 - [InstCombine] fold mul of zext bools to 'and'

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2020-07-03T13:14:18-04:00
New Revision: 40fcc42498d8877d2d2a8548f3ac5c052b2723c2

URL: https://github.com/llvm/llvm-project/commit/40fcc42498d8877d2d2a8548f3ac5c052b2723c2
DIFF: https://github.com/llvm/llvm-project/commit/40fcc42498d8877d2d2a8548f3ac5c052b2723c2.diff

LOG: [InstCombine] fold mul of zext bools to 'and'

The base case only works because we are relying on a
poison-unsafe select transform; if that is fixed, we
would regress on patterns like this.

The extra use tests show that the select transform can't
be applied consistently. So it may be a regression to have
an extra instruction on 1 test, but that result was not
created safely and does not happen reliably.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
    llvm/test/Transforms/InstCombine/mul.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 2d4fdd3eeb40..39b6c6765fad 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -366,6 +366,14 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
     }
   }
 
+  // (zext bool X) * (zext bool Y) --> zext (and X, Y)
+  if (match(Op0, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1) &&
+      match(Op1, m_ZExt(m_Value(Y))) && Y->getType()->isIntOrIntVectorTy(1) &&
+      (Op0->hasOneUse() || Op1->hasOneUse())) {
+    Value *And = Builder.CreateAnd(X, Y, "mulbool");
+    return CastInst::Create(Instruction::ZExt, And, I.getType());
+  }
+
   // (bool X) * Y --> X ? Y : 0
   // Y * (bool X) --> X ? Y : 0
   if (match(Op0, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1))

diff  --git a/llvm/test/Transforms/InstCombine/mul.ll b/llvm/test/Transforms/InstCombine/mul.ll
index c98a089734de..fd2e472e9a07 100644
--- a/llvm/test/Transforms/InstCombine/mul.ll
+++ b/llvm/test/Transforms/InstCombine/mul.ll
@@ -129,8 +129,8 @@ define <2 x i32> @mul_bool_vec_commute(<2 x i32> %x, <2 x i1> %y) {
 
 define <3 x i7> @mul_bools(<3 x i1> %x, <3 x i1> %y) {
 ; CHECK-LABEL: @mul_bools(
-; CHECK-NEXT:    [[NARROW:%.*]] = and <3 x i1> [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = zext <3 x i1> [[NARROW]] to <3 x i7>
+; CHECK-NEXT:    [[MULBOOL:%.*]] = and <3 x i1> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = zext <3 x i1> [[MULBOOL]] to <3 x i7>
 ; CHECK-NEXT:    ret <3 x i7> [[R]]
 ;
   %zx = zext <3 x i1> %x to <3 x i7>
@@ -143,7 +143,8 @@ define i32 @mul_bools_use1(i1 %x, i1 %y) {
 ; CHECK-LABEL: @mul_bools_use1(
 ; CHECK-NEXT:    [[ZY:%.*]] = zext i1 [[Y:%.*]] to i32
 ; CHECK-NEXT:    call void @use32(i32 [[ZY]])
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[X:%.*]], i32 [[ZY]], i32 0
+; CHECK-NEXT:    [[MULBOOL:%.*]] = and i1 [[X:%.*]], [[Y]]
+; CHECK-NEXT:    [[R:%.*]] = zext i1 [[MULBOOL]] to i32
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %zx = zext i1 %x to i32
@@ -157,8 +158,8 @@ define i32 @mul_bools_use2(i1 %x, i1 %y) {
 ; CHECK-LABEL: @mul_bools_use2(
 ; CHECK-NEXT:    [[ZY:%.*]] = zext i1 [[Y:%.*]] to i32
 ; CHECK-NEXT:    call void @use32(i32 [[ZY]])
-; CHECK-NEXT:    [[NARROW:%.*]] = and i1 [[Y]], [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = zext i1 [[NARROW]] to i32
+; CHECK-NEXT:    [[MULBOOL:%.*]] = and i1 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = zext i1 [[MULBOOL]] to i32
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %zx = zext i1 %x to i32