[llvm] ca7ffaa - [ConstantRange] add nuw support to truncate (NFC) (#152990)
Andreas Jonson via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 12 03:26:45 PDT 2025
Author: Andreas Jonson
Date: 2025-08-12T12:26:35+02:00
New Revision: ca7ffaaeeb54bc350b8e48f4f35b68902dc9868c
URL: https://github.com/llvm/llvm-project/commit/ca7ffaaeeb54bc350b8e48f4f35b68902dc9868c
DIFF: https://github.com/llvm/llvm-project/commit/ca7ffaaeeb54bc350b8e48f4f35b68902dc9868c.diff
LOG: [ConstantRange] add nuw support to truncate (NFC) (#152990)
Added:
Modified:
llvm/include/llvm/IR/ConstantRange.h
llvm/lib/IR/ConstantRange.cpp
llvm/unittests/IR/ConstantRangeTest.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/ConstantRange.h b/llvm/include/llvm/IR/ConstantRange.h
index 9a6a9db65688a..4b2fda364fdf4 100644
--- a/llvm/include/llvm/IR/ConstantRange.h
+++ b/llvm/include/llvm/IR/ConstantRange.h
@@ -380,8 +380,9 @@ class [[nodiscard]] ConstantRange {
/// Return a new range in the specified integer type, which must be
/// strictly smaller than the current type. The returned range will
/// correspond to the possible range of values if the source range had been
- /// truncated to the specified type.
- LLVM_ABI ConstantRange truncate(uint32_t BitWidth) const;
+ /// truncated to the specified type with wrap type \p NoWrapKind.
+ LLVM_ABI ConstantRange truncate(uint32_t BitWidth,
+ unsigned NoWrapKind = 0) const;
/// Make this range have the bit width given by \p BitWidth. The
/// value is zero extended, truncated, or left alone to make it that width.
diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index 2fcdbcc6a3db2..b454c9a4cd3ae 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -872,7 +872,8 @@ ConstantRange ConstantRange::signExtend(uint32_t DstTySize) const {
return ConstantRange(Lower.sext(DstTySize), Upper.sext(DstTySize));
}
-ConstantRange ConstantRange::truncate(uint32_t DstTySize) const {
+ConstantRange ConstantRange::truncate(uint32_t DstTySize,
+ unsigned NoWrapKind) const {
assert(getBitWidth() > DstTySize && "Not a value truncation");
if (isEmptySet())
return getEmpty(DstTySize);
@@ -886,22 +887,36 @@ ConstantRange ConstantRange::truncate(uint32_t DstTySize) const {
// We use the non-wrapped set code to analyze the [Lower, MaxValue) part, and
// then we do the union with [MaxValue, Upper)
if (isUpperWrapped()) {
- // If Upper is greater than or equal to MaxValue(DstTy), it covers the whole
- // truncated range.
- if (Upper.getActiveBits() > DstTySize || Upper.countr_one() == DstTySize)
+ // If Upper is greater than MaxValue(DstTy), it covers the whole truncated
+ // range.
+ if (Upper.getActiveBits() > DstTySize)
return getFull(DstTySize);
- Union = ConstantRange(APInt::getMaxValue(DstTySize),Upper.trunc(DstTySize));
- UpperDiv.setAllBits();
-
- // Union covers the MaxValue case, so return if the remaining range is just
- // MaxValue(DstTy).
- if (LowerDiv == UpperDiv)
- return Union;
+ // For nuw the two parts are: [0, Upper) \/ [Lower, MaxValue(DstTy)]
+ if (NoWrapKind & TruncInst::NoUnsignedWrap) {
+ Union = ConstantRange(APInt::getZero(DstTySize), Upper.trunc(DstTySize));
+ UpperDiv = APInt::getOneBitSet(getBitWidth(), DstTySize);
+ } else {
+ // If Upper is equal to MaxValue(DstTy), it covers the whole truncated
+ // range.
+ if (Upper.countr_one() == DstTySize)
+ return getFull(DstTySize);
+ Union =
+ ConstantRange(APInt::getMaxValue(DstTySize), Upper.trunc(DstTySize));
+ UpperDiv.setAllBits();
+ // Union covers the MaxValue case, so return if the remaining range is
+ // just MaxValue(DstTy).
+ if (LowerDiv == UpperDiv)
+ return Union;
+ }
}
// Chop off the most significant bits that are past the destination bitwidth.
if (LowerDiv.getActiveBits() > DstTySize) {
+ // For trunc nuw if LowerDiv is greater than MaxValue(DstTy), the range is
+ // outside the whole truncated range.
+ if (NoWrapKind & TruncInst::NoUnsignedWrap)
+ return Union;
// Mask to just the signficant bits and subtract from LowerDiv/UpperDiv.
APInt Adjust = LowerDiv & APInt::getBitsSetFrom(getBitWidth(), DstTySize);
LowerDiv -= Adjust;
@@ -913,6 +928,10 @@ ConstantRange ConstantRange::truncate(uint32_t DstTySize) const {
return ConstantRange(LowerDiv.trunc(DstTySize),
UpperDiv.trunc(DstTySize)).unionWith(Union);
+ if (!LowerDiv.isZero() && NoWrapKind & TruncInst::NoUnsignedWrap)
+ return ConstantRange(LowerDiv.trunc(DstTySize), APInt::getZero(DstTySize))
+ .unionWith(Union);
+
// The truncated value wraps around. Check if we can do better than fullset.
if (UpperDivWidth == DstTySize + 1) {
// Clear the MSB so that UpperDiv wraps around.
diff --git a/llvm/unittests/IR/ConstantRangeTest.cpp b/llvm/unittests/IR/ConstantRangeTest.cpp
index bcb5d498c8cb9..53d581c8db7c9 100644
--- a/llvm/unittests/IR/ConstantRangeTest.cpp
+++ b/llvm/unittests/IR/ConstantRangeTest.cpp
@@ -451,6 +451,65 @@ TEST_F(ConstantRangeTest, Trunc) {
EXPECT_EQ(SevenOne.truncate(2), ConstantRange(APInt(2, 3), APInt(2, 1)));
}
+TEST_F(ConstantRangeTest, TruncNuw) {
+ auto Range = [](unsigned NumBits, unsigned Lower, unsigned Upper) {
+ return ConstantRange(APInt(NumBits, Lower), APInt(NumBits, Upper));
+ };
+ // trunc([0, 4), 3->2) = full
+ EXPECT_TRUE(
+ Range(3, 0, 4).truncate(2, TruncInst::NoUnsignedWrap).isFullSet());
+ // trunc([0, 3), 3->2) = [0, 3)
+ EXPECT_EQ(Range(3, 0, 3).truncate(2, TruncInst::NoUnsignedWrap),
+ Range(2, 0, 3));
+ // trunc([1, 3), 3->2) = [1, 3)
+ EXPECT_EQ(Range(3, 1, 3).truncate(2, TruncInst::NoUnsignedWrap),
+ Range(2, 1, 3));
+ // trunc([1, 5), 3->2) = [1, 0)
+ EXPECT_EQ(Range(3, 1, 5).truncate(2, TruncInst::NoUnsignedWrap),
+ Range(2, 1, 0));
+ // trunc([4, 7), 3->2) = empty
+ EXPECT_TRUE(
+ Range(3, 4, 7).truncate(2, TruncInst::NoUnsignedWrap).isEmptySet());
+ // trunc([4, 0), 3->2) = empty
+ EXPECT_TRUE(
+ Range(3, 4, 0).truncate(2, TruncInst::NoUnsignedWrap).isEmptySet());
+ // trunc([4, 1), 3->2) = [0, 1)
+ EXPECT_EQ(Range(3, 4, 1).truncate(2, TruncInst::NoUnsignedWrap),
+ Range(2, 0, 1));
+ // trunc([3, 1), 3->2) = [3, 1)
+ EXPECT_EQ(Range(3, 3, 1).truncate(2, TruncInst::NoUnsignedWrap),
+ Range(2, 3, 1));
+ // trunc([3, 0), 3->2) = [3, 0)
+ EXPECT_EQ(Range(3, 3, 0).truncate(2, TruncInst::NoUnsignedWrap),
+ Range(2, 3, 0));
+ // trunc([1, 0), 2->1) = [1, 0)
+ EXPECT_EQ(Range(2, 1, 0).truncate(1, TruncInst::NoUnsignedWrap),
+ Range(1, 1, 0));
+ // trunc([2, 1), 2->1) = [0, 1)
+ EXPECT_EQ(Range(2, 2, 1).truncate(1, TruncInst::NoUnsignedWrap),
+ Range(1, 0, 1));
+}
+
+TEST_F(ConstantRangeTest, TruncNuwExhaustive) {
+ EnumerateConstantRanges(4, [&](const ConstantRange &CR) {
+ unsigned NumBits = 3;
+ ConstantRange Trunc = CR.truncate(NumBits, TruncInst::NoUnsignedWrap);
+ SmallBitVector Elems(1 << NumBits);
+ ForeachNumInConstantRange(CR, [&](const APInt &N) {
+ if (N.isIntN(NumBits))
+ Elems.set(N.getZExtValue());
+ });
+ TestRange(Trunc, Elems, PreferSmallest, {CR});
+ });
+ EnumerateConstantRanges(3, [&](const ConstantRange &CR) {
+ ConstantRange Trunc = CR.truncate(1, TruncInst::NoUnsignedWrap);
+ EXPECT_EQ(CR.contains(APInt::getZero(3)),
+ Trunc.contains(APInt::getZero(1)));
+ EXPECT_EQ(CR.contains(APInt::getOneBitSet(3, 0)),
+ Trunc.contains(APInt::getAllOnes(1)));
+ });
+}
+
TEST_F(ConstantRangeTest, ZExt) {
ConstantRange ZFull = Full.zeroExtend(20);
ConstantRange ZEmpty = Empty.zeroExtend(20);
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