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InstCombine: Combine (X | Y) - X to (~X & Y) 

This implements the transformation from (X | Y) - X to (~X & Y).

Differential Revision: http://reviews.llvm.org/D5791

llvm-svn: 221129
This commit is contained in:
David Majnemer 2014-11-03 05:53:55 +00:00
parent d301b9b3e0
commit 72a643dc8f
2 changed files with 25 additions and 6 deletions
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21
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -1431,11 +1431,11 @@ Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
Z2 = dyn_cast<Constant>(B2); B = B1;
} else if (match(B1, m_AnyZero()) && match(A2, m_AnyZero())) {
Z1 = dyn_cast<Constant>(B1); B = B2;
Z2 = dyn_cast<Constant>(A2); A = A1;
Z2 = dyn_cast<Constant>(A2); A = A1;
}
if (Z1 && Z2 &&
(I.hasNoSignedZeros() ||
if (Z1 && Z2 &&
(I.hasNoSignedZeros() ||
(Z1->isNegativeZeroValue() && Z2->isNegativeZeroValue()))) {
return SelectInst::Create(C, A, B);
}
@ -1594,7 +1594,7 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
// -(X >>u 31) -> (X >>s 31)
// -(X >>s 31) -> (X >>u 31)
if (C->isZero()) {
Value *X;
Value *X;
ConstantInt *CI;
if (match(Op1, m_LShr(m_Value(X), m_ConstantInt(CI))) &&
// Verify we are shifting out everything but the sign bit.
@ -1609,7 +1609,7 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
}
{
{
Value *Y;
// X-(X+Y) == -Y X-(Y+X) == -Y
if (match(Op1, m_Add(m_Specific(Op0), m_Value(Y))) ||
@ -1630,6 +1630,15 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
return BinaryOperator::CreateAnd(A, B);
}
if (Op0->hasOneUse()) {
Value *Y = nullptr;
// ((X | Y) - X) --> (~X & Y)
if (match(Op0, m_Or(m_Value(Y), m_Specific(Op1))) ||
match(Op0, m_Or(m_Specific(Op1), m_Value(Y))))
return BinaryOperator::CreateAnd(
Y, Builder->CreateNot(Op1, Op1->getName() + ".not"));
}
if (Op1->hasOneUse()) {
Value *X = nullptr, *Y = nullptr, *Z = nullptr;
Constant *C = nullptr;

10
llvm/test/Transforms/InstCombine/sub.ll
View File

@ -540,3 +540,13 @@ define i32 @test45(i32 %x, i32 %y) {
; CHECK-NEXT: %sub = and i32 %x, %y
; CHECK: ret i32 %sub
}
define i32 @test46(i32 %x, i32 %y) {
%or = or i32 %x, %y
%sub = sub i32 %or, %x
ret i32 %sub
; CHECK-LABEL: @test46(
; CHECK-NEXT: %x.not = xor i32 %x, -1
; CHECK-NEXT: %sub = and i32 %y, %x.not
; CHECK: ret i32 %sub
}