nikic created this revision.
nikic added a reviewer: lebedev.ri.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.
Add support for abs() to ConstantRange. This will allow to handle abs select flavor in LVI and I think it will also come in handy for srem implementation.
The implementation is slightly tricky, because a) abs of signed min is signed min and b) sign-wrapped ranges may have an abs() that is smaller than a full range, so we need to explicitly handle them.
Repository:
rL LLVM
https://reviews.llvm.org/D61084
Files:
llvm/include/llvm/IR/ConstantRange.h
llvm/lib/IR/ConstantRange.cpp
llvm/unittests/IR/ConstantRangeTest.cpp
Index: llvm/unittests/IR/ConstantRangeTest.cpp
===================================================================
--- llvm/unittests/IR/ConstantRangeTest.cpp
+++ llvm/unittests/IR/ConstantRangeTest.cpp
@@ -1787,4 +1787,30 @@
});
}
+TEST_F(ConstantRangeTest, Abs) {
+ unsigned Bits = 4;
+ EnumerateConstantRanges(Bits, [&](const ConstantRange &CR) {
+ // We're working with unsigned integers here, because it makes the signed
+ // min case non-wrapping.
+ APInt Min = APInt::getMaxValue(Bits);
+ APInt Max = APInt::getMinValue(Bits);
+ ForeachNumInConstantRange(CR, [&](const APInt &N) {
+ APInt AbsN = N.abs();
+ if (AbsN.ult(Min))
+ Min = AbsN;
+ if (AbsN.ugt(Max))
+ Max = AbsN;
+ });
+
+ ConstantRange AbsCR = CR.abs();
+ if (Min.ugt(Max)) {
+ EXPECT_TRUE(AbsCR.isEmptySet());
+ return;
+ }
+
+ ConstantRange Exact = ConstantRange::getNonEmpty(Min, Max + 1);
+ EXPECT_EQ(Exact, AbsCR);
+ });
+}
+
} // anonymous namespace
Index: llvm/lib/IR/ConstantRange.cpp
===================================================================
--- llvm/lib/IR/ConstantRange.cpp
+++ llvm/lib/IR/ConstantRange.cpp
@@ -1158,6 +1158,37 @@
return ConstantRange(Upper, Lower);
}
+ConstantRange ConstantRange::abs() const {
+ if (isEmptySet())
+ return getEmpty();
+
+ if (isSignWrappedSet()) {
+ APInt Lo;
+ // Check whether the range crosses zero.
+ if (Upper.isStrictlyPositive() || !Lower.isStrictlyPositive())
+ Lo = APInt::getNullValue(getBitWidth());
+ else
+ Lo = APIntOps::umin(Lower, -Upper + 1);
+
+ // SignedMin is included in the result range.
+ return ConstantRange(Lo, APInt::getSignedMinValue(getBitWidth()) + 1);
+ }
+
+ APInt SMin = getSignedMin(), SMax = getSignedMax();
+
+ // All non-negative.
+ if (SMin.isNonNegative())
+ return *this;
+
+ // All negative.
+ if (SMax.isNegative())
+ return ConstantRange(-SMax, -SMin + 1);
+
+ // Range crosses zero.
+ return ConstantRange(APInt::getNullValue(getBitWidth()),
+ APIntOps::umax(-SMin, SMax) + 1);
+}
+
ConstantRange::OverflowResult ConstantRange::unsignedAddMayOverflow(
const ConstantRange &Other) const {
if (isEmptySet() || Other.isEmptySet())
Index: llvm/include/llvm/IR/ConstantRange.h
===================================================================
--- llvm/include/llvm/IR/ConstantRange.h
+++ llvm/include/llvm/IR/ConstantRange.h
@@ -397,6 +397,10 @@
/// Return a new range that is the logical not of the current set.
ConstantRange inverse() const;
+ /// Calculate absolute value range. If the original range contains signed
+ /// min, then the resulting range will also contain signed min.
+ ConstantRange abs() const;
+
/// Represents whether an operation on the given constant range is known to
/// always or never overflow.
enum class OverflowResult { AlwaysOverflows, MayOverflow, NeverOverflows };
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