[llvm] r313819 - [InstCombine] Handle (X & C2) < C1 --> (X & C2) == 0
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 20 14:18:17 PDT 2017
Author: ctopper
Date: Wed Sep 20 14:18:17 2017
New Revision: 313819
URL: http://llvm.org/viewvc/llvm-project?rev=313819&view=rev
Log:
[InstCombine] Handle (X & C2) < C1 --> (X & C2) == 0
We already did (X & C2) > C1 --> (X & C2) != 0, if any bit set in (X & C2) will produce a result greater than C1. But there is an equivalent inverse condition with <= C1 (which will be canonicalized to < C1+1)
Differential Revision: https://reviews.llvm.org/D38065
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/trunk/test/Transforms/InstCombine/icmp.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=313819&r1=313818&r2=313819&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Wed Sep 20 14:18:17 2017
@@ -1715,12 +1715,19 @@ Instruction *InstCombiner::foldICmpAndCo
}
// (X & C2) > C1 --> (X & C2) != 0, if any bit set in (X & C2) will produce a
- // result greater than C1.
- unsigned NumTZ = C2->countTrailingZeros();
- if (Cmp.getPredicate() == ICmpInst::ICMP_UGT && NumTZ < C2->getBitWidth() &&
- NumTZ >= C1->getActiveBits()) {
- Constant *Zero = Constant::getNullValue(And->getType());
- return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
+ // result greater than C1. Also handle (X & C2) < C1 --> (X & C2) == 0.
+ if (!C2->isNullValue()) {
+ unsigned NumTZ = C2->countTrailingZeros();
+ if (Cmp.getPredicate() == ICmpInst::ICMP_UGT &&
+ NumTZ >= C1->getActiveBits()) {
+ Constant *Zero = Constant::getNullValue(And->getType());
+ return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
+ }
+ if (Cmp.getPredicate() == ICmpInst::ICMP_ULT &&
+ NumTZ >= C1->ceilLogBase2()) {
+ Constant *Zero = Constant::getNullValue(And->getType());
+ return new ICmpInst(ICmpInst::ICMP_EQ, And, Zero);
+ }
}
return nullptr;
Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=313819&r1=313818&r2=313819&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Wed Sep 20 14:18:17 2017
@@ -1141,7 +1141,7 @@ define i1 @test67(i32 %x) {
define i1 @test67inverse(i32 %x) {
; CHECK-LABEL: @test67inverse(
; CHECK-NEXT: [[AND:%.*]] = and i32 [[X:%.*]], 96
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[AND]], 32
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[AND]], 0
; CHECK-NEXT: ret i1 [[CMP]]
;
%and = and i32 %x, 127
@@ -1178,7 +1178,7 @@ define <2 x i1> @test67vec2(<2 x i32> %x
define <2 x i1> @test67vecinverse(<2 x i32> %x) {
; CHECK-LABEL: @test67vecinverse(
; CHECK-NEXT: [[AND:%.*]] = and <2 x i32> [[X:%.*]], <i32 96, i32 96>
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult <2 x i32> [[AND]], <i32 32, i32 32>
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq <2 x i32> [[AND]], zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[CMP]]
;
%and = and <2 x i32> %x, <i32 96, i32 96>
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