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InstCombine: Squash an icmp+select into bitwise arithmetic

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(X & INT_MIN) == 0 ? X ^ INT_MIN : X  into  X | INT_MIN
(X & INT_MIN) != 0 ? X ^ INT_MIN : X  into  X & INT_MAX

This fixes PR21993.

llvm-svn: 224676
This commit is contained in:
David Majnemer 2014-12-20 04:45:35 +00:00
parent 46b6fd2884
commit 3da9d34415
2 changed files with 57 additions and 6 deletions
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30
lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@ -617,26 +617,44 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
}
}
{
if (unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits()) {
APInt MinSignedValue = APInt::getSignBit(BitWidth);
Value *X;
const APInt *Y, *C;
if (match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) &&
bool TrueWhenUnset;
bool IsBitTest = false;
if (ICmpInst::isEquality(Pred) &&
match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) &&
match(CmpRHS, m_Zero())) {
IsBitTest = true;
TrueWhenUnset = Pred == ICmpInst::ICMP_EQ;
} else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) {
X = CmpLHS;
Y = &MinSignedValue;
IsBitTest = true;
TrueWhenUnset = false;
} else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) {
X = CmpLHS;
Y = &MinSignedValue;
IsBitTest = true;
TrueWhenUnset = true;
}
if (IsBitTest) {
Value *V = nullptr;
// (X & Y) == 0 ? X : X ^ Y --> X & ~Y
if (Pred == ICmpInst::ICMP_EQ && TrueVal == X &&
if (TrueWhenUnset && TrueVal == X &&
match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
V = Builder->CreateAnd(X, ~(*Y));
// (X & Y) != 0 ? X ^ Y : X --> X & ~Y
else if (Pred == ICmpInst::ICMP_NE && FalseVal == X &&
else if (!TrueWhenUnset && FalseVal == X &&
match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
V = Builder->CreateAnd(X, ~(*Y));
// (X & Y) == 0 ? X ^ Y : X --> X | Y
else if (Pred == ICmpInst::ICMP_EQ && FalseVal == X &&
else if (TrueWhenUnset && FalseVal == X &&
match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
V = Builder->CreateOr(X, *Y);
// (X & Y) != 0 ? X : X ^ Y --> X | Y
else if (Pred == ICmpInst::ICMP_NE && TrueVal == X &&
else if (!TrueWhenUnset && TrueVal == X &&
match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
V = Builder->CreateOr(X, *Y);

33
test/Transforms/InstCombine/select.ll
View File

@ -1050,6 +1050,39 @@ define i64 @select_icmp_x_and_8_ne_0_y_or_8(i32 %x, i64 %y) {
ret i64 %or.y
}
; CHECK-LABEL: @select_icmp_and_2147483648_ne_0_xor_2147483648(
; CHECK-NEXT: [[AND:%[a-z0-9]+]] = and i32 %x, 2147483647
; CHECK-NEXT: ret i32 [[AND]]
define i32 @select_icmp_and_2147483648_ne_0_xor_2147483648(i32 %x) {
%and = and i32 %x, 2147483648
%cmp = icmp eq i32 %and, 0
%xor = xor i32 %x, 2147483648
%x.xor = select i1 %cmp, i32 %x, i32 %xor
ret i32 %x.xor
}
; CHECK-LABEL: @select_icmp_and_2147483648_eq_0_xor_2147483648(
; CHECK-NEXT: [[OR:%[a-z0-9]+]] = or i32 %x, -2147483648
; CHECK-NEXT: ret i32 [[OR]]
define i32 @select_icmp_and_2147483648_eq_0_xor_2147483648(i32 %x) {
%and = and i32 %x, 2147483648
%cmp = icmp eq i32 %and, 0
%xor = xor i32 %x, 2147483648
%xor.x = select i1 %cmp, i32 %xor, i32 %x
ret i32 %xor.x
}
; CHECK-LABEL: @select_icmp_x_and_2147483648_ne_0_or_2147483648(
; CHECK: xor i32 %1, -2147483648
; CHECK: or i32 %2, %x
define i32 @select_icmp_x_and_2147483648_ne_0_or_2147483648(i32 %x) {
%and = and i32 %x, 2147483648
%cmp = icmp eq i32 %and, 0
%or = or i32 %x, 2147483648
%or.x = select i1 %cmp, i32 %or, i32 %x
ret i32 %or.x
}
define i32 @test65(i64 %x) {
%1 = and i64 %x, 16
%2 = icmp ne i64 %1, 0