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Fold icmp ugt (udiv X, Y), X to false. Spotted by my super-optimizer

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in 186.crafty.

llvm-svn: 143209
This commit is contained in:
Duncan Sands 2011-10-28 18:17:44 +00:00
parent 3dd6c949a5
commit 5730fe6a31
2 changed files with 36 additions and 0 deletions
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12
lib/Analysis/InstructionSimplify.cpp
View File

@ -1574,6 +1574,9 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
// 'srem x, CI2' produces (-|CI2|, |CI2|).
Upper = CI2->getValue().abs();
Lower = (-Upper) + 1;
} else if (match(LHS, m_UDiv(m_ConstantInt(CI2), m_Value()))) {
// 'udiv CI2, x' produces [0, CI2].
Upper = CI2->getValue();
} else if (match(LHS, m_UDiv(m_Value(), m_ConstantInt(CI2)))) {
// 'udiv x, CI2' produces [0, UINT_MAX / CI2].
APInt NegOne = APInt::getAllOnesValue(Width);
@ -1880,6 +1883,15 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
}
}
// x udiv y <=u x.
if (LBO && match(LBO, m_UDiv(m_Specific(RHS), m_Value()))) {
// icmp pred (X /u Y), X
if (Pred == ICmpInst::ICMP_UGT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_ULE)
return getTrue(ITy);
}
if (MaxRecurse && LBO && RBO && LBO->getOpcode() == RBO->getOpcode() &&
LBO->getOperand(1) == RBO->getOperand(1)) {
switch (LBO->getOpcode()) {

24
test/Transforms/InstSimplify/compare.ll
View File

@ -300,6 +300,30 @@ define i1 @udiv2(i32 %X, i32 %Y, i32 %Z) {
; CHECK: ret i1 true
}
define i1 @udiv3(i32 %X, i32 %Y) {
; CHECK: @udiv3
%A = udiv i32 %X, %Y
%C = icmp ugt i32 %A, %X
ret i1 %C
; CHECK: ret i1 false
}
define i1 @udiv4(i32 %X, i32 %Y) {
; CHECK: @udiv4
%A = udiv i32 %X, %Y
%C = icmp ule i32 %A, %X
ret i1 %C
; CHECK: ret i1 true
}
define i1 @udiv5(i32 %X) {
; CHECK: @udiv5
%A = udiv i32 123, %X
%C = icmp ugt i32 %A, 124
ret i1 %C
; CHECK: ret i1 false
}
define i1 @sdiv1(i32 %X) {
; CHECK: @sdiv1
%A = sdiv i32 %X, 1000000