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[ValueTracking] Extend known bits to understand @llvm.bitreverse.

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Differential Revision: https://reviews.llvm.org/D28780

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292233 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chad Rosier 2017-01-17 17:23:51 +00:00
parent 518607fa99
commit 7eb6751ff6
3 changed files with 70 additions and 0 deletions
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5
lib/Analysis/ValueTracking.cpp
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@ -1400,6 +1400,11 @@ static void computeKnownBitsFromOperator(const Operator *I, APInt &KnownZero,
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::bitreverse:
computeKnownBits(I->getOperand(0), KnownZero2, KnownOne2, Depth + 1, Q);
KnownZero = KnownZero2.reverseBits();
KnownOne = KnownOne2.reverseBits();
break;
case Intrinsic::bswap:
computeKnownBits(I->getOperand(0), KnownZero2, KnownOne2, Depth + 1, Q);
KnownZero |= KnownZero2.byteSwap();

34
test/Transforms/InstCombine/bitreverse-known-bits.ll Normal file
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@ -0,0 +1,34 @@
; RUN: opt < %s -S -instcombine | FileCheck %s
declare i32 @llvm.bitreverse.i32(i32)
; CHECK-LABEL: @test1
; CHECK: ret i1 true
define i1 @test1(i32 %arg) {
%a = or i32 %arg, 4294901760
%b = call i32 @llvm.bitreverse.i32(i32 %a)
%and = and i32 %b, 65535
%res = icmp eq i32 %and, 65535
ret i1 %res
}
; CHECK-LABEL: @test2
; CHECK: ret i1 true
define i1 @test2(i32 %arg) {
%a = or i32 %arg, 1
%b = call i32 @llvm.bitreverse.i32(i32 %a)
%c = and i32 %b, 2147483648
%d = call i32 @llvm.bitreverse.i32(i32 %c)
%res = icmp eq i32 %d, 1
ret i1 %res
}
; CHECK-LABEL: @test3
; CHECK: ret i1 false
define i1 @test3(i32 %arg) {
%a = or i32 %arg, 65536
%b = call i32 @llvm.bitreverse.i32(i32 %a)
%and = and i32 %b, 32768
%res = icmp eq i32 %and, 0
ret i1 %res
}

31
test/Transforms/InstSimplify/bitreverse.ll Normal file
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@ -0,0 +1,31 @@
; RUN: opt < %s -S -instsimplify | FileCheck %s
declare i32 @llvm.bitreverse.i32(i32)
; CHECK-LABEL: @test1(
; CHECK: ret i1 false
define i1 @test1(i32 %arg) {
%a = or i32 %arg, 1
%b = call i32 @llvm.bitreverse.i32(i32 %a)
%res = icmp eq i32 %b, 0
ret i1 %res
}
; CHECK-LABEL: @test2(
; CHECK: ret i1 false
define i1 @test2(i32 %arg) {
%a = or i32 %arg, 1024
%b = call i32 @llvm.bitreverse.i32(i32 %a)
%res = icmp eq i32 %b, 0
ret i1 %res
}
; CHECK-LABEL: @test3(
; CHECK: ret i1 false
define i1 @test3(i32 %arg) {
%a = and i32 %arg, 1
%b = call i32 @llvm.bitreverse.i32(i32 %a)
%and = and i32 %b, 1
%res = icmp eq i32 %and, 1
ret i1 %res
}