Reapply [ValueTracking] Support min/max selects in computeConstantRange()
Add support for min/max flavor selects in computeConstantRange(),
which allows us to fold comparisons of a min/max against a constant
in InstSimplify. This fixes an infinite InstCombine loop, with the
test case taken from D59378.
Relative to the previous iteration, this contains some adjustments for
AMDGPU med3 tests: The AMDGPU target runs InstSimplify prior to codegen,
which ends up constant folding some existing med3 tests after this
change. To preserve these tests a hidden -amdgpu-scalar-ir-passes option
is added, which allows disabling scalar IR passes (that use InstSimplify)
for testing purposes.
Differential Revision: https://reviews.llvm.org/D59506
llvm-svn: 357870
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d3cbd07..e18679c 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -5689,7 +5689,28 @@
return;
}
- // TODO Handle min/max flavors.
+ const APInt *C;
+ if (!match(LHS, m_APInt(C)) && !match(RHS, m_APInt(C)))
+ return;
+
+ switch (R.Flavor) {
+ case SPF_UMIN:
+ Upper = *C + 1;
+ break;
+ case SPF_UMAX:
+ Lower = *C;
+ break;
+ case SPF_SMIN:
+ Lower = APInt::getSignedMinValue(BitWidth);
+ Upper = *C + 1;
+ break;
+ case SPF_SMAX:
+ Lower = *C;
+ Upper = APInt::getSignedMaxValue(BitWidth) + 1;
+ break;
+ default:
+ break;
+ }
}
ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo) {