[ConstantRange] Improve ConstantRange::binaryXor #80146
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@llvm/pr-subscribers-llvm-transforms Author: Yingwei Zheng (dtcxzyw) Changes
Alive2: https://alive2.llvm.org/ce/z/bmTMV9 Full diff: https://github.com/llvm/llvm-project/pull/80146.diff 2 Files Affected:
diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index cbb64b299e648..f951bd9b8354d 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -1467,7 +1467,28 @@ ConstantRange ConstantRange::binaryXor(const ConstantRange &Other) const {
if (isSingleElement() && getSingleElement()->isAllOnes())
return Other.binaryNot();
- return fromKnownBits(toKnownBits() ^ Other.toKnownBits(), /*IsSigned*/false);
+ KnownBits LHSKnown = toKnownBits();
+ KnownBits RHSKnown = Other.toKnownBits();
+ KnownBits Known = LHSKnown ^ RHSKnown;
+ ConstantRange CR = fromKnownBits(Known, /*IsSigned*/ false);
+ // Typically the following code doesn't improve the result if BW = 1.
+ if (getBitWidth() == 1)
+ return CR;
+
+ // If LHS is known to be the subset of RHS, treat LHS ^ RHS as RHS -nuw/nsw
+ // LHS. If RHS is known to be the subset of LHS, treat LHS ^ RHS as LHS
+ // -nuw/nsw RHS.
+ if (LHSKnown.getMaxValue().isSubsetOf(RHSKnown.getMinValue()))
+ CR = CR.intersectWith(
+ Other.subWithNoWrap(*this, OverflowingBinaryOperator::NoUnsignedWrap |
+ OverflowingBinaryOperator::NoSignedWrap),
+ PreferredRangeType::Unsigned);
+ else if (RHSKnown.getMaxValue().isSubsetOf(LHSKnown.getMinValue()))
+ CR = CR.intersectWith(
+ subWithNoWrap(Other, OverflowingBinaryOperator::NoUnsignedWrap |
+ OverflowingBinaryOperator::NoSignedWrap),
+ PreferredRangeType::Unsigned);
+ return CR;
}
ConstantRange
diff --git a/llvm/test/Transforms/SCCP/pr79696.ll b/llvm/test/Transforms/SCCP/pr79696.ll
new file mode 100644
index 0000000000000..a860112d5ef36
--- /dev/null
+++ b/llvm/test/Transforms/SCCP/pr79696.ll
@@ -0,0 +1,55 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt < %s -passes=ipsccp -S | FileCheck %s
+
+; Tests from PR79696
+
+define i1 @constant_range_xor(i64 %a) {
+; CHECK-LABEL: define i1 @constant_range_xor(
+; CHECK-SAME: i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[A]], 8192
+; CHECK-NEXT: br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK: then:
+; CHECK-NEXT: [[CTLZ:%.*]] = call i64 @llvm.ctlz.i64(i64 [[A]], i1 true)
+; CHECK-NEXT: [[CONV:%.*]] = xor i64 [[CTLZ]], 63
+; CHECK-NEXT: ret i1 false
+; CHECK: else:
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cmp = icmp ugt i64 %a, 8192
+ br i1 %cmp, label %then, label %else
+then:
+ %ctlz = call i64 @llvm.ctlz.i64(i64 %a, i1 true) ;[0, 50]
+ %conv = xor i64 %ctlz, 63 ;[13, 63]
+ %cmp1 = icmp ult i64 %conv, 13
+ ret i1 %cmp1
+else:
+ ret i1 false
+}
+
+define i1 @constant_range_xor_negative(i64 %a) {
+; CHECK-LABEL: define i1 @constant_range_xor_negative(
+; CHECK-SAME: i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[A]], 8192
+; CHECK-NEXT: br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK: then:
+; CHECK-NEXT: [[CTLZ:%.*]] = call i64 @llvm.ctlz.i64(i64 [[A]], i1 true)
+; CHECK-NEXT: [[CONV:%.*]] = xor i64 [[CTLZ]], 62
+; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i64 [[CONV]], 13
+; CHECK-NEXT: ret i1 [[CMP1]]
+; CHECK: else:
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cmp = icmp ugt i64 %a, 8192
+ br i1 %cmp, label %then, label %else
+then:
+ %ctlz = call i64 @llvm.ctlz.i64(i64 %a, i1 true) ;[0, 50]
+ %conv = xor i64 %ctlz, 62 ;[12, 63]
+ %cmp1 = icmp ult i64 %conv, 13
+ ret i1 %cmp1
+else:
+ ret i1 false
+}
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@llvm/pr-subscribers-llvm-ir Author: Yingwei Zheng (dtcxzyw) Changes
Alive2: https://alive2.llvm.org/ce/z/bmTMV9 Full diff: https://github.com/llvm/llvm-project/pull/80146.diff 2 Files Affected:
diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index cbb64b299e648..f951bd9b8354d 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -1467,7 +1467,28 @@ ConstantRange ConstantRange::binaryXor(const ConstantRange &Other) const {
if (isSingleElement() && getSingleElement()->isAllOnes())
return Other.binaryNot();
- return fromKnownBits(toKnownBits() ^ Other.toKnownBits(), /*IsSigned*/false);
+ KnownBits LHSKnown = toKnownBits();
+ KnownBits RHSKnown = Other.toKnownBits();
+ KnownBits Known = LHSKnown ^ RHSKnown;
+ ConstantRange CR = fromKnownBits(Known, /*IsSigned*/ false);
+ // Typically the following code doesn't improve the result if BW = 1.
+ if (getBitWidth() == 1)
+ return CR;
+
+ // If LHS is known to be the subset of RHS, treat LHS ^ RHS as RHS -nuw/nsw
+ // LHS. If RHS is known to be the subset of LHS, treat LHS ^ RHS as LHS
+ // -nuw/nsw RHS.
+ if (LHSKnown.getMaxValue().isSubsetOf(RHSKnown.getMinValue()))
+ CR = CR.intersectWith(
+ Other.subWithNoWrap(*this, OverflowingBinaryOperator::NoUnsignedWrap |
+ OverflowingBinaryOperator::NoSignedWrap),
+ PreferredRangeType::Unsigned);
+ else if (RHSKnown.getMaxValue().isSubsetOf(LHSKnown.getMinValue()))
+ CR = CR.intersectWith(
+ subWithNoWrap(Other, OverflowingBinaryOperator::NoUnsignedWrap |
+ OverflowingBinaryOperator::NoSignedWrap),
+ PreferredRangeType::Unsigned);
+ return CR;
}
ConstantRange
diff --git a/llvm/test/Transforms/SCCP/pr79696.ll b/llvm/test/Transforms/SCCP/pr79696.ll
new file mode 100644
index 0000000000000..a860112d5ef36
--- /dev/null
+++ b/llvm/test/Transforms/SCCP/pr79696.ll
@@ -0,0 +1,55 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt < %s -passes=ipsccp -S | FileCheck %s
+
+; Tests from PR79696
+
+define i1 @constant_range_xor(i64 %a) {
+; CHECK-LABEL: define i1 @constant_range_xor(
+; CHECK-SAME: i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[A]], 8192
+; CHECK-NEXT: br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK: then:
+; CHECK-NEXT: [[CTLZ:%.*]] = call i64 @llvm.ctlz.i64(i64 [[A]], i1 true)
+; CHECK-NEXT: [[CONV:%.*]] = xor i64 [[CTLZ]], 63
+; CHECK-NEXT: ret i1 false
+; CHECK: else:
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cmp = icmp ugt i64 %a, 8192
+ br i1 %cmp, label %then, label %else
+then:
+ %ctlz = call i64 @llvm.ctlz.i64(i64 %a, i1 true) ;[0, 50]
+ %conv = xor i64 %ctlz, 63 ;[13, 63]
+ %cmp1 = icmp ult i64 %conv, 13
+ ret i1 %cmp1
+else:
+ ret i1 false
+}
+
+define i1 @constant_range_xor_negative(i64 %a) {
+; CHECK-LABEL: define i1 @constant_range_xor_negative(
+; CHECK-SAME: i64 [[A:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[A]], 8192
+; CHECK-NEXT: br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK: then:
+; CHECK-NEXT: [[CTLZ:%.*]] = call i64 @llvm.ctlz.i64(i64 [[A]], i1 true)
+; CHECK-NEXT: [[CONV:%.*]] = xor i64 [[CTLZ]], 62
+; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i64 [[CONV]], 13
+; CHECK-NEXT: ret i1 [[CMP1]]
+; CHECK: else:
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cmp = icmp ugt i64 %a, 8192
+ br i1 %cmp, label %then, label %else
+then:
+ %ctlz = call i64 @llvm.ctlz.i64(i64 %a, i1 true) ;[0, 50]
+ %conv = xor i64 %ctlz, 62 ;[12, 63]
+ %cmp1 = icmp ult i64 %conv, 13
+ ret i1 %cmp1
+else:
+ ret i1 false
+}
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dtcxzyw
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ConstantRange::binaryXorgives poor results as it currently depends onKnownBits::operator^.Since
sub A, Bis canonicalized intoxor A, BifBis the subset ofA, this patch reverts the transform inConstantRange::binaryXor, which will give better results.Alive2: https://alive2.llvm.org/ce/z/bmTMV9
Fixes #79696.