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[ConstantRange] Make getEquivalentICmp smarter

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This change teaches getEquivalentICmp to be smarter about generating
ICMP_NE and ICMP_EQ predicates.

An earlier version of this change was landed as rL283057 which had a
use-after-free bug.  This new version has a fix for that bug, and a (C++
unittests/) test case that would have triggered it rL283057.

llvm-svn: 283078
This commit is contained in:
Sanjoy Das 2016-10-02 20:59:05 +00:00
parent cc2b5dd90f
commit 26178861cc
3 changed files with 61 additions and 0 deletions
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8
include/llvm/IR/ConstantRange.h
View File

@ -166,6 +166,14 @@ public:
return nullptr;
}
/// If this set contains all but a single element, return it, otherwise return
/// null.
const APInt *getSingleMissingElement() const {
if (Lower == Upper + 1)
return &Upper;
return nullptr;
}
/// Return true if this set contains exactly one member.
///
bool isSingleElement() const { return getSingleElement() != nullptr; }

8
lib/IR/ConstantRange.cpp
View File

@ -147,6 +147,14 @@ bool ConstantRange::getEquivalentICmp(CmpInst::Predicate &Pred,
Pred = isEmptySet() ? CmpInst::ICMP_ULT : CmpInst::ICMP_UGE;
RHS = APInt(getBitWidth(), 0);
Success = true;
} else if (auto *OnlyElt = getSingleElement()) {
Pred = CmpInst::ICMP_EQ;
RHS = *OnlyElt;
Success = true;
} else if (auto *OnlyMissingElt = getSingleMissingElement()) {
Pred = CmpInst::ICMP_NE;
RHS = *OnlyMissingElt;
Success = true;
} else if (getLower().isMinSignedValue() || getLower().isMinValue()) {
Pred =
getLower().isMinSignedValue() ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT;

45
unittests/IR/ConstantRangeTest.cpp
View File

@ -102,10 +102,19 @@ TEST_F(ConstantRangeTest, Equality) {
TEST_F(ConstantRangeTest, SingleElement) {
EXPECT_EQ(Full.getSingleElement(), static_cast<APInt *>(nullptr));
EXPECT_EQ(Empty.getSingleElement(), static_cast<APInt *>(nullptr));
EXPECT_EQ(Full.getSingleMissingElement(), static_cast<APInt *>(nullptr));
EXPECT_EQ(Empty.getSingleMissingElement(), static_cast<APInt *>(nullptr));
EXPECT_EQ(*One.getSingleElement(), APInt(16, 0xa));
EXPECT_EQ(Some.getSingleElement(), static_cast<APInt *>(nullptr));
EXPECT_EQ(Wrap.getSingleElement(), static_cast<APInt *>(nullptr));
EXPECT_EQ(One.getSingleMissingElement(), static_cast<APInt *>(nullptr));
EXPECT_EQ(Some.getSingleMissingElement(), static_cast<APInt *>(nullptr));
ConstantRange OneInverse = One.inverse();
EXPECT_EQ(*OneInverse.getSingleMissingElement(), *One.getSingleElement());
EXPECT_FALSE(Full.isSingleElement());
EXPECT_FALSE(Empty.isSingleElement());
EXPECT_TRUE(One.isSingleElement());
@ -760,6 +769,42 @@ TEST(ConstantRange, GetEquivalentICmp) {
EXPECT_FALSE(ConstantRange(APInt::getMinValue(32) - APInt(32, 100),
APInt::getMinValue(32) + APInt(32, 100))
.getEquivalentICmp(Pred, RHS));
EXPECT_TRUE(ConstantRange(APInt(32, 100)).getEquivalentICmp(Pred, RHS));
EXPECT_EQ(Pred, CmpInst::ICMP_EQ);
EXPECT_EQ(RHS, APInt(32, 100));
EXPECT_TRUE(
ConstantRange(APInt(32, 100)).inverse().getEquivalentICmp(Pred, RHS));
EXPECT_EQ(Pred, CmpInst::ICMP_NE);
EXPECT_EQ(RHS, APInt(32, 100));
EXPECT_TRUE(
ConstantRange(APInt(512, 100)).inverse().getEquivalentICmp(Pred, RHS));
EXPECT_EQ(Pred, CmpInst::ICMP_NE);
EXPECT_EQ(RHS, APInt(512, 100));
// NB! It would be correct for the following four calls to getEquivalentICmp
// to return ordered predicates like CmpInst::ICMP_ULT or CmpInst::ICMP_UGT.
// However, that's not the case today.
EXPECT_TRUE(ConstantRange(APInt(32, 0)).getEquivalentICmp(Pred, RHS));
EXPECT_EQ(Pred, CmpInst::ICMP_EQ);
EXPECT_EQ(RHS, APInt(32, 0));
EXPECT_TRUE(
ConstantRange(APInt(32, 0)).inverse().getEquivalentICmp(Pred, RHS));
EXPECT_EQ(Pred, CmpInst::ICMP_NE);
EXPECT_EQ(RHS, APInt(32, 0));
EXPECT_TRUE(ConstantRange(APInt(32, -1)).getEquivalentICmp(Pred, RHS));
EXPECT_EQ(Pred, CmpInst::ICMP_EQ);
EXPECT_EQ(RHS, APInt(32, -1));
EXPECT_TRUE(
ConstantRange(APInt(32, -1)).inverse().getEquivalentICmp(Pred, RHS));
EXPECT_EQ(Pred, CmpInst::ICMP_NE);
EXPECT_EQ(RHS, APInt(32, -1));
}
} // anonymous namespace