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[GuardWidening] Use getEquivalentICmp to fold constant compares

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`ConstantRange::getEquivalentICmp` is more general, and better
factored.

llvm-svn: 270019
This commit is contained in:
Sanjoy Das 2016-05-19 03:53:17 +00:00
parent c63bcd9d33
commit b590ade35e
2 changed files with 67 additions and 13 deletions
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34
lib/Transforms/Scalar/GuardWidening.cpp
View File

@ -356,21 +356,31 @@ bool GuardWideningImpl::widenCondCommon(Value *Cond0, Value *Cond1,
if (match(Cond0, m_ICmp(Pred0, m_Value(LHS), m_ConstantInt(RHS0))) && if (match(Cond0, m_ICmp(Pred0, m_Value(LHS), m_ConstantInt(RHS0))) &&
match(Cond1, m_ICmp(Pred1, m_Specific(LHS), m_ConstantInt(RHS1)))) { match(Cond1, m_ICmp(Pred1, m_Specific(LHS), m_ConstantInt(RHS1)))) {
// TODO: This logic should be generalized and refactored into a new ConstantRange CR0 =
// Constant::getEquivalentICmp helper. ConstantRange::makeExactICmpRegion(Pred0, RHS0->getValue());
if (Pred0 == ICmpInst::ICMP_NE && RHS0->isZero()) ConstantRange CR1 =
Pred0 = ICmpInst::ICMP_UGT; ConstantRange::makeExactICmpRegion(Pred1, RHS1->getValue());
if (Pred1 == ICmpInst::ICMP_NE && RHS1->isZero())
Pred1 = ICmpInst::ICMP_UGT;
if (Pred0 == ICmpInst::ICMP_UGT && Pred1 == ICmpInst::ICMP_UGT) { // SubsetIntersect is a subset of the actual mathematical intersection of
// CR0 and CR1, while SupersetIntersect is a superset of the the actual
// mathematical intersection. If these two ConstantRanges are equal, then
// we know we were able to represent the actual mathematical intersection
// of CR0 and CR1, and can use the same to generate an icmp instruction.
//
// Given what we're doing here and the semantics of guards, it would
// actually be correct to just use SubsetIntersect, but that may be too
// aggressive in cases we care about.
auto SubsetIntersect = CR0.inverse().unionWith(CR1.inverse()).inverse();
auto SupersetIntersect = CR0.intersectWith(CR1);
APInt NewRHSAP;
CmpInst::Predicate Pred;
if (SubsetIntersect == SupersetIntersect &&
SubsetIntersect.getEquivalentICmp(Pred, NewRHSAP)) {
if (InsertPt) { if (InsertPt) {
ConstantInt *NewRHS = ConstantInt *NewRHS = ConstantInt::get(Cond0->getContext(), NewRHSAP);
RHS0->getValue().ugt(RHS1->getValue()) ? RHS0 : RHS1; Result = new ICmpInst(InsertPt, Pred, LHS, NewRHS, "wide.chk");
Result = new ICmpInst(InsertPt, ICmpInst::ICMP_UGT, LHS, NewRHS,
"wide.chk");
} }
return true; return true;
} }
} }

46
test/Transforms/GuardWidening/basic.ll
View File

@ -126,7 +126,7 @@ leave:
define void @f_5(i32 %a) { define void @f_5(i32 %a) {
; CHECK-LABEL: @f_5( ; CHECK-LABEL: @f_5(
entry: entry:
; CHECK: %wide.chk = icmp ugt i32 %a, 10 ; CHECK: %wide.chk = icmp uge i32 %a, 11
; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %wide.chk) [ "deopt"() ] ; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %wide.chk) [ "deopt"() ]
; CHECK: br i1 undef, label %left, label %right ; CHECK: br i1 undef, label %left, label %right
@ -335,3 +335,47 @@ entry:
call void(i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ] call void(i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
ret void ret void
} }
define void @f_13(i32 %a) {
; CHECK-LABEL: @f_13(
entry:
; CHECK: %wide.chk = icmp ult i32 %a, 10
; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %wide.chk) [ "deopt"() ]
; CHECK: br i1 undef, label %left, label %right
%cond_0 = icmp ult i32 %a, 14
call void(i1, ...) @llvm.experimental.guard(i1 %cond_0) [ "deopt"() ]
br i1 undef, label %left, label %right
left:
%cond_1 = icmp slt i32 %a, 10
call void(i1, ...) @llvm.experimental.guard(i1 %cond_1) [ "deopt"() ]
ret void
right:
ret void
}
define void @f_14(i32 %a) {
; CHECK-LABEL: @f_14(
entry:
; CHECK: %cond_0 = icmp ult i32 %a, 14
; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %cond_0) [ "deopt"() ]
; CHECK: br i1 undef, label %left, label %right
%cond_0 = icmp ult i32 %a, 14
call void(i1, ...) @llvm.experimental.guard(i1 %cond_0) [ "deopt"() ]
br i1 undef, label %left, label %right
left:
; CHECK: left:
; CHECK: %cond_1 = icmp sgt i32 %a, 10
; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %cond_1) [ "deopt"() ]
%cond_1 = icmp sgt i32 %a, 10
call void(i1, ...) @llvm.experimental.guard(i1 %cond_1) [ "deopt"() ]
ret void
right:
ret void
}