[ConstantRange] Fix single bit abs range (PR59887)

For a full range input, we would produce an empty range instead
of a full range. The change to the SMin.isNonNegative() branch is
an optimality fix, because we should account for the potentially
discarded SMin value in the IntMinIsPoison case.

Change TestUnaryOpExhaustive to test both 4 and 1 bits, to both
cover this specific case in unit tests, and make sure all other
unary operations deal with 1-bit inputs correctly.

Fixes https://github.com/llvm/llvm-project/issues/59887.

diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index 2f0d3d1e3a5ac8c164f262f60f5384d3020f04b8..0dbccaa1a66aa0fd7702f3610077b7894a833fdf 100644 (file)
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -1656,15 +1656,15 @@ ConstantRange ConstantRange::abs(bool IntMinIsPoison) const {
 
   // All non-negative.
   if (SMin.isNonNegative())
-    return *this;
+    return ConstantRange(SMin, SMax + 1);
 
   // All negative.
   if (SMax.isNegative())
     return ConstantRange(-SMax, -SMin + 1);
 
   // Range crosses zero.
-  return ConstantRange(APInt::getZero(getBitWidth()),
-                       APIntOps::umax(-SMin, SMax) + 1);
+  return ConstantRange::getNonEmpty(APInt::getZero(getBitWidth()),
+                                    APIntOps::umax(-SMin, SMax) + 1);
 }
 
 ConstantRange::OverflowResult ConstantRange::unsignedAddMayOverflow(

diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/abs.ll b/llvm/test/Transforms/CorrelatedValuePropagation/abs.ll
index 47ed7892b5d3f250548bf793c03d6d38118b410b..6231b05a851cb3f21a159032045f70f9272995c6 100644 (file)
--- a/llvm/test/Transforms/CorrelatedValuePropagation/abs.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/abs.ll
@@ -381,7 +381,7 @@ define i1 @pr59887(i1 %x, i1 %c) {
 ; CHECK-LABEL: @pr59887(
 ; CHECK-NEXT:    [[ABS:%.*]] = call i1 @llvm.abs.i1(i1 [[X:%.*]], i1 false)
 ; CHECK-NEXT:    [[RES:%.*]] = select i1 [[C:%.*]], i1 [[ABS]], i1 false
-; CHECK-NEXT:    ret i1 false
+; CHECK-NEXT:    ret i1 [[RES]]
 ;
   %abs = call i1 @llvm.abs.i1(i1 %x, i1 false)
   %res = select i1 %c, i1 %abs, i1 false

diff --git a/llvm/unittests/IR/ConstantRangeTest.cpp b/llvm/unittests/IR/ConstantRangeTest.cpp
index cb53801851d42b396657fe6858483783bb4408e9..45398ec6a61762f526578bdefcdcdaf27f7d7344 100644 (file)
--- a/llvm/unittests/IR/ConstantRangeTest.cpp
+++ b/llvm/unittests/IR/ConstantRangeTest.cpp
@@ -179,15 +179,16 @@ using UnaryIntFn = llvm::function_ref<std::optional<APInt>(const APInt &)>;
 
 static void TestUnaryOpExhaustive(UnaryRangeFn RangeFn, UnaryIntFn IntFn,
                                   PreferFn PreferenceFn = PreferSmallest) {
-  unsigned Bits = 4;
-  EnumerateConstantRanges(Bits, [&](const ConstantRange &CR) {
-    SmallBitVector Elems(1 << Bits);
-    ForeachNumInConstantRange(CR, [&](const APInt &N) {
-      if (std::optional<APInt> ResultN = IntFn(N))
-        Elems.set(ResultN->getZExtValue());
+  for (unsigned Bits : {1, 4}) {
+    EnumerateConstantRanges(Bits, [&](const ConstantRange &CR) {
+      SmallBitVector Elems(1 << Bits);
+      ForeachNumInConstantRange(CR, [&](const APInt &N) {
+        if (std::optional<APInt> ResultN = IntFn(N))
+          Elems.set(ResultN->getZExtValue());
+      });
+      TestRange(RangeFn(CR), Elems, PreferenceFn, {CR});
     });
-    TestRange(RangeFn(CR), Elems, PreferenceFn, {CR});
-  });
+  }
 }
 
 using BinaryRangeFn = llvm::function_ref<ConstantRange(const ConstantRange &,