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Fold "icmp pred (srem X, Y), Y" like we do for urem. Handle signed comparisons

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in the urem case, though not the other way around. This is enough to get #3 from
PR9343!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126991 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-03-04 10:06:52 +00:00
parent 3a73e343d0
commit 786792784e
3 changed files with 59 additions and 3 deletions
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31
lib/Analysis/InstructionSimplify.cpp
View File

@ -1671,14 +1671,28 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
}
}
if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) {
Value *V;
if (LBO && match(LBO, m_URem(m_Value(V), m_Specific(RHS)))) {
bool KnownNonNegative, KnownNegative;
switch (Pred) {
default:
break;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE:
ComputeSignBit(LHS, KnownNonNegative, KnownNegative, TD);
if (!KnownNonNegative)
break;
// fall-through
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE:
return ConstantInt::getFalse(RHS->getContext());
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE:
ComputeSignBit(LHS, KnownNonNegative, KnownNegative, TD);
if (!KnownNonNegative)
break;
// fall-through
case ICmpInst::ICMP_NE:
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE:
@ -1686,6 +1700,21 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
}
}
if (LBO && match(LBO, m_SRem(m_Value(), m_Specific(RHS)))) {
switch (Pred) {
default:
break;
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE:
return ConstantInt::getFalse(RHS->getContext());
case ICmpInst::ICMP_NE:
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE:
return ConstantInt::getTrue(RHS->getContext());
}
}
// If the comparison is with the result of a select instruction, check whether
// comparing with either branch of the select always yields the same value.
if (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))

13
test/Transforms/InstCombine/icmp.ll
View File

@ -379,7 +379,7 @@ define i1 @test38(i32 %x, i32 %y, i32 %z) {
}
; PR9343 #1
; CHECK: test39
; CHECK: @test39
; CHECK %B = icmp eq i32 %X, 0
define i1 @test39(i32 %X, i32 %Y) {
%A = ashr exact i32 %X, %Y
@ -387,10 +387,19 @@ define i1 @test39(i32 %X, i32 %Y) {
ret i1 %B
}
; CHECK: test40
; CHECK: @test40
; CHECK: %B = icmp ne i32 %X, 0
define i1 @test40(i32 %X, i32 %Y) {
%A = lshr exact i32 %X, %Y
%B = icmp ne i32 %A, 0
ret i1 %B
}
; PR9343 #3
; CHECK: @test41
; CHECK: ret i1 true
define i1 @test41(i32 %X, i32 %Y) {
%A = urem i32 %X, %Y
%B = icmp ugt i32 %Y, %A
ret i1 %B
}

18
test/Transforms/InstSimplify/compare.ll
View File

@ -236,6 +236,15 @@ define i1 @urem4(i32 %X) {
; CHECK: ret i1 %B
}
define i1 @urem5(i16 %X, i32 %Y) {
; CHECK: @urem5
%A = zext i16 %X to i32
%B = urem i32 %A, %Y
%C = icmp slt i32 %B, %Y
ret i1 %C
; CHECK: ret i1 true
}
define i1 @srem1(i32 %X) {
; CHECK: @srem1
%A = srem i32 %X, -5
@ -244,6 +253,15 @@ define i1 @srem1(i32 %X) {
; CHECK: ret i1 false
}
define i1 @srem2(i32 %X, i32 %Y) {
; CHECK: @srem2
%neg = sub i32 %Y, 0
%A = srem i32 %X, %Y
%B = icmp slt i32 %A, %neg
ret i1 %B
; CHECK: ret i1 true
}
define i1 @udiv1(i32 %X) {
; CHECK: @udiv1
%A = udiv i32 %X, 1000000