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[ConstantRange] Split makeICmpRegion in two. 

Summary:
This change splits `makeICmpRegion` into `makeAllowedICmpRegion` and
`makeSatisfyingICmpRegion` with slightly different contracts.  The first
one is useful for determining what values some expression //may// take,
given that a certain `icmp` evaluates to true.  The second one is useful
for determining what values are guaranteed to //satisfy// a given
`icmp`.

Reviewers: nlewycky

Reviewed By: nlewycky

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8345

llvm-svn: 232575
This commit is contained in:
Sanjoy Das 2015-03-18 00:41:24 +00:00
parent cba49d4b04
commit 7182d36f66
6 changed files with 96 additions and 20 deletions
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29
llvm/include/llvm/IR/ConstantRange.h
View File

@ -33,6 +33,7 @@
#define LLVM_IR_CONSTANTRANGE_H
#include "llvm/ADT/APInt.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/Support/DataTypes.h"
namespace llvm {
@ -59,15 +60,27 @@ public:
/// assert out if the two APInt's are not the same bit width.
ConstantRange(APIntMoveTy Lower, APIntMoveTy Upper);
/// Produce the smallest range that contains all values that
/// might satisfy the comparison specified by Pred when compared to any value
/// contained within Other.
/// Produce the smallest range such that all values that may satisfy the given
/// predicate with any value contained within Other is contained in the
/// returned range. Formally, this returns a superset of
/// 'union over all y in Other . { x : icmp op x y is true }'. If the exact
/// answer is not representable as a ConstantRange, the return value will be a
/// proper superset of the above.
///
/// Solves for range X in 'for all x in X, there exists a y in Y such that
/// icmp op x, y is true'. Every value that might make the comparison true
/// is included in the resulting range.
static ConstantRange makeICmpRegion(unsigned Pred,
const ConstantRange &Other);
/// Example: Pred = ult and Other = i8 [2, 5) returns Result = [0, 4)
static ConstantRange makeAllowedICmpRegion(CmpInst::Predicate Pred,
const ConstantRange &Other);
/// Produce the largest range such that all values in the returned range
/// satisfy the given predicate with all values contained within Other.
/// Formally, this returns a subset of
/// 'intersection over all y in Other . { x : icmp op x y is true }'. If the
/// exact answer is not representable as a ConstantRange, the return value
/// will be a proper subset of the above.
///
/// Example: Pred = ult and Other = i8 [2, 5) returns [0, 2)
static ConstantRange makeSatisfyingICmpRegion(CmpInst::Predicate Pred,
const ConstantRange &Other);
/// Return the lower value for this range.
///

4
llvm/lib/Analysis/LazyValueInfo.cpp
View File

@ -854,10 +854,10 @@ bool getValueFromFromCondition(Value *Val, ICmpInst *ICI,
ConstantInt *CI = dyn_cast<ConstantInt>(ICI->getOperand(1));
if (CI && (ICI->getOperand(0) == Val || NegOffset)) {
// Calculate the range of values that would satisfy the comparison.
// Calculate the range of values that are allowed by the comparison
ConstantRange CmpRange(CI->getValue());
ConstantRange TrueValues =
ConstantRange::makeICmpRegion(ICI->getPredicate(), CmpRange);
ConstantRange::makeAllowedICmpRegion(ICI->getPredicate(), CmpRange);
if (NegOffset) // Apply the offset from above.
TrueValues = TrueValues.subtract(NegOffset->getValue());

17
llvm/lib/IR/ConstantRange.cpp
View File

@ -49,14 +49,15 @@ ConstantRange::ConstantRange(APIntMoveTy L, APIntMoveTy U)
"Lower == Upper, but they aren't min or max value!");
}
ConstantRange ConstantRange::makeICmpRegion(unsigned Pred,
const ConstantRange &CR) {
ConstantRange ConstantRange::makeAllowedICmpRegion(CmpInst::Predicate Pred,
const ConstantRange &CR) {
if (CR.isEmptySet())
return CR;
uint32_t W = CR.getBitWidth();
switch (Pred) {
default: llvm_unreachable("Invalid ICmp predicate to makeICmpRegion()");
default:
llvm_unreachable("Invalid ICmp predicate to makeAllowedICmpRegion()");
case CmpInst::ICMP_EQ:
return CR;
case CmpInst::ICMP_NE:
@ -114,6 +115,16 @@ ConstantRange ConstantRange::makeICmpRegion(unsigned Pred,
}
}
ConstantRange ConstantRange::makeSatisfyingICmpRegion(CmpInst::Predicate Pred,
const ConstantRange &CR) {
// Follows from De-Morgan's laws:
//
// ~(~A union ~B) == A intersect B.
//
return makeAllowedICmpRegion(CmpInst::getInversePredicate(Pred), CR)
.inverse();
}
/// isFullSet - Return true if this set contains all of the elements possible
/// for this data-type
bool ConstantRange::isFullSet() const {

4
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -979,9 +979,9 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) {
// Make a constant range that's the intersection of the two icmp ranges.
// If the intersection is empty, we know that the result is false.
ConstantRange LHSRange =
ConstantRange::makeICmpRegion(LHSCC, LHSCst->getValue());
ConstantRange::makeAllowedICmpRegion(LHSCC, LHSCst->getValue());
ConstantRange RHSRange =
ConstantRange::makeICmpRegion(RHSCC, RHSCst->getValue());
ConstantRange::makeAllowedICmpRegion(RHSCC, RHSCst->getValue());
if (LHSRange.intersectWith(RHSRange).isEmptySet())
return ConstantInt::get(CmpInst::makeCmpResultType(LHS->getType()), 0);

4
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -421,8 +421,8 @@ private:
}
// If we have "x ult 3", for example, then we can add 0,1,2 to the set.
ConstantRange Span = ConstantRange::makeICmpRegion(ICI->getPredicate(),
C->getValue());
ConstantRange Span = ConstantRange::makeAllowedICmpRegion(
ICI->getPredicate(), C->getValue());
// Shift the range if the compare is fed by an add. This is the range
// compare idiom as emitted by instcombine.

58
llvm/unittests/IR/ConstantRangeTest.cpp
View File

@ -509,11 +509,63 @@ TEST_F(ConstantRangeTest, Lshr) {
EXPECT_EQ(Wrap.lshr(Wrap), Full);
}
TEST(ConstantRange, MakeICmpRegion) {
TEST(ConstantRange, MakeAllowedICmpRegion) {
// PR8250
ConstantRange SMax = ConstantRange(APInt::getSignedMaxValue(32));
EXPECT_TRUE(ConstantRange::makeICmpRegion(ICmpInst::ICMP_SGT,
SMax).isEmptySet());
EXPECT_TRUE(ConstantRange::makeAllowedICmpRegion(ICmpInst::ICMP_SGT, SMax)
.isEmptySet());
}
TEST(ConstantRange, MakeSatisfyingICmpRegion) {
ConstantRange LowHalf(APInt(8, 0), APInt(8, 128));
ConstantRange HighHalf(APInt(8, 128), APInt(8, 0));
ConstantRange EmptySet(8, /* isFullSet = */ false);
EXPECT_EQ(ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_NE, LowHalf),
HighHalf);
EXPECT_EQ(
ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_NE, HighHalf),
LowHalf);
EXPECT_TRUE(ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_EQ,
HighHalf).isEmptySet());
ConstantRange UnsignedSample(APInt(8, 5), APInt(8, 200));
EXPECT_EQ(ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_ULT,
UnsignedSample),
ConstantRange(APInt(8, 0), APInt(8, 5)));
EXPECT_EQ(ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_ULE,
UnsignedSample),
ConstantRange(APInt(8, 0), APInt(8, 6)));
EXPECT_EQ(ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_UGT,
UnsignedSample),
ConstantRange(APInt(8, 200), APInt(8, 0)));
EXPECT_EQ(ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_UGE,
UnsignedSample),
ConstantRange(APInt(8, 199), APInt(8, 0)));
ConstantRange SignedSample(APInt(8, -5), APInt(8, 5));
EXPECT_EQ(
ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_SLT, SignedSample),
ConstantRange(APInt(8, -128), APInt(8, -5)));
EXPECT_EQ(
ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_SLE, SignedSample),
ConstantRange(APInt(8, -128), APInt(8, -4)));
EXPECT_EQ(
ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_SGT, SignedSample),
ConstantRange(APInt(8, 5), APInt(8, -128)));
EXPECT_EQ(
ConstantRange::makeSatisfyingICmpRegion(ICmpInst::ICMP_SGE, SignedSample),
ConstantRange(APInt(8, 4), APInt(8, -128)));
}
} // anonymous namespace