[llvm] afd44bb - [InstCombine] fold ctlz/cttz of bool types

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2021-06-13T08:26:40-04:00
New Revision: afd44bb6f29ca11b87b76349709fdee2ecd9d921

URL: https://github.com/llvm/llvm-project/commit/afd44bb6f29ca11b87b76349709fdee2ecd9d921
DIFF: https://github.com/llvm/llvm-project/commit/afd44bb6f29ca11b87b76349709fdee2ecd9d921.diff

LOG: [InstCombine] fold ctlz/cttz of bool types

https://alive2.llvm.org/ce/z/tX4pUT

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
    llvm/test/Transforms/InstCombine/intrinsics.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 193730e06edc5..c5911fc507d9c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -444,6 +444,16 @@ static Instruction *foldCttzCtlz(IntrinsicInst &II, InstCombinerImpl &IC) {
     return CallInst::Create(F, {X, II.getArgOperand(1)});
   }
 
+  if (II.getType()->isIntOrIntVectorTy(1)) {
+    // ctlz/cttz i1 Op0 --> not Op0
+    if (match(Op1, m_Zero()))
+      return BinaryOperator::CreateNot(Op0);
+    // If zero is undef, then the input can be assumed to be "true", so the
+    // instruction simplifies to "false".
+    assert(match(Op1, m_One()) && "Expected ctlz/cttz operand to be 0 or 1");
+    return IC.replaceInstUsesWith(II, ConstantInt::getNullValue(II.getType()));
+  }
+
   if (IsTZ) {
     // cttz(-x) -> cttz(x)
     if (match(Op0, m_Neg(m_Value(X))))

diff  --git a/llvm/test/Transforms/InstCombine/intrinsics.ll b/llvm/test/Transforms/InstCombine/intrinsics.ll
index 2c28bc265326c..1039ed2c2f29f 100644
--- a/llvm/test/Transforms/InstCombine/intrinsics.ll
+++ b/llvm/test/Transforms/InstCombine/intrinsics.ll
@@ -61,7 +61,7 @@ define <2 x i32> @cttz_vec(<2 x i32> %a) {
 ; Make sure we don't add range metadata to i1 cttz.
 define i1 @cttz_i1(i1 %arg) {
 ; CHECK-LABEL: @cttz_i1(
-; CHECK-NEXT:    [[CNT:%.*]] = call i1 @llvm.cttz.i1(i1 [[ARG:%.*]], i1 false) #[[ATTR2:[0-9]+]]
+; CHECK-NEXT:    [[CNT:%.*]] = xor i1 [[ARG:%.*]], true
 ; CHECK-NEXT:    ret i1 [[CNT]]
 ;
   %cnt = call i1 @llvm.cttz.i1(i1 %arg, i1 false) nounwind readnone
@@ -78,7 +78,7 @@ define i1 @cttz_i1_zero_is_undef(i1 %arg) {
 
 define <2 x i1> @cttz_v2i1(<2 x i1> %arg) {
 ; CHECK-LABEL: @cttz_v2i1(
-; CHECK-NEXT:    [[CNT:%.*]] = call <2 x i1> @llvm.cttz.v2i1(<2 x i1> [[ARG:%.*]], i1 false) #[[ATTR2]]
+; CHECK-NEXT:    [[CNT:%.*]] = xor <2 x i1> [[ARG:%.*]], <i1 true, i1 true>
 ; CHECK-NEXT:    ret <2 x i1> [[CNT]]
 ;
   %cnt = call <2 x i1> @llvm.cttz.v2i1(<2 x i1> %arg, i1 false) nounwind readnone
@@ -87,8 +87,7 @@ define <2 x i1> @cttz_v2i1(<2 x i1> %arg) {
 
 define <2 x i1> @cttz_v2i1_zero_is_undef(<2 x i1> %arg) {
 ; CHECK-LABEL: @cttz_v2i1_zero_is_undef(
-; CHECK-NEXT:    [[CNT:%.*]] = call <2 x i1> @llvm.cttz.v2i1(<2 x i1> [[ARG:%.*]], i1 true) #[[ATTR2]]
-; CHECK-NEXT:    ret <2 x i1> [[CNT]]
+; CHECK-NEXT:    ret <2 x i1> zeroinitializer
 ;
   %cnt = call <2 x i1> @llvm.cttz.v2i1(<2 x i1> %arg, i1 true) nounwind readnone
   ret <2 x i1> %cnt
@@ -117,7 +116,7 @@ define <2 x i1> @cttz_knownbits_vec(<2 x i32> %arg) {
 define i32 @cttz_knownbits2(i32 %arg) {
 ; CHECK-LABEL: @cttz_knownbits2(
 ; CHECK-NEXT:    [[OR:%.*]] = or i32 [[ARG:%.*]], 4
-; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.cttz.i32(i32 [[OR]], i1 true) #[[ATTR2]], !range [[RNG0:![0-9]+]]
+; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.cttz.i32(i32 [[OR]], i1 true) #[[ATTR2:[0-9]+]], !range [[RNG0:![0-9]+]]
 ; CHECK-NEXT:    ret i32 [[CNT]]
 ;
   %or = or i32 %arg, 4
@@ -179,7 +178,7 @@ define <2 x i8> @ctlz_vec(<2 x i8> %a) {
 ; Make sure we don't add range metadata to i1 ctlz.
 define i1 @ctlz_i1(i1 %arg) {
 ; CHECK-LABEL: @ctlz_i1(
-; CHECK-NEXT:    [[CNT:%.*]] = call i1 @llvm.ctlz.i1(i1 [[ARG:%.*]], i1 false) #[[ATTR2]]
+; CHECK-NEXT:    [[CNT:%.*]] = xor i1 [[ARG:%.*]], true
 ; CHECK-NEXT:    ret i1 [[CNT]]
 ;
   %cnt = call i1 @llvm.ctlz.i1(i1 %arg, i1 false) nounwind readnone
@@ -196,7 +195,7 @@ define i1 @ctlz_i1_zero_is_undef(i1 %arg) {
 
 define <2 x i1> @ctlz_v2i1(<2 x i1> %arg) {
 ; CHECK-LABEL: @ctlz_v2i1(
-; CHECK-NEXT:    [[CNT:%.*]] = call <2 x i1> @llvm.ctlz.v2i1(<2 x i1> [[ARG:%.*]], i1 false) #[[ATTR2]]
+; CHECK-NEXT:    [[CNT:%.*]] = xor <2 x i1> [[ARG:%.*]], <i1 true, i1 true>
 ; CHECK-NEXT:    ret <2 x i1> [[CNT]]
 ;
   %cnt = call <2 x i1> @llvm.ctlz.v2i1(<2 x i1> %arg, i1 false) nounwind readnone
@@ -205,8 +204,7 @@ define <2 x i1> @ctlz_v2i1(<2 x i1> %arg) {
 
 define <2 x i1> @ctlz_v2i1_zero_is_undef(<2 x i1> %arg) {
 ; CHECK-LABEL: @ctlz_v2i1_zero_is_undef(
-; CHECK-NEXT:    [[CNT:%.*]] = call <2 x i1> @llvm.ctlz.v2i1(<2 x i1> [[ARG:%.*]], i1 true) #[[ATTR2]]
-; CHECK-NEXT:    ret <2 x i1> [[CNT]]
+; CHECK-NEXT:    ret <2 x i1> zeroinitializer
 ;
   %cnt = call <2 x i1> @llvm.ctlz.v2i1(<2 x i1> %arg, i1 true) nounwind readnone
   ret <2 x i1> %cnt