[llvm] 796efa8 - [Float2Int] Fix pessimization in the MinBW calculation. (#86051)
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Thu Mar 21 11:09:43 PDT 2024
Author: Craig Topper
Date: 2024-03-21T11:09:40-07:00
New Revision: 796efa8cd5800a42eb8362564be64f3d72512a05
URL: https://github.com/llvm/llvm-project/commit/796efa8cd5800a42eb8362564be64f3d72512a05
DIFF: https://github.com/llvm/llvm-project/commit/796efa8cd5800a42eb8362564be64f3d72512a05.diff
LOG: [Float2Int] Fix pessimization in the MinBW calculation. (#86051)
The MinBW was being calculated using the significant bits of the upper
and lower bounds. The upper bound is 1 past the last value in the range
so I don't think it should be included. Instead use ConstantRange::getMinSignedBits.
I'm still not sure if the +1 is needed after the getMinSignedBits call.
Added:
Modified:
llvm/lib/Transforms/Scalar/Float2Int.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/Float2Int.cpp b/llvm/lib/Transforms/Scalar/Float2Int.cpp
index ccca8bcc1a56ac..de8c05d5689f5b 100644
--- a/llvm/lib/Transforms/Scalar/Float2Int.cpp
+++ b/llvm/lib/Transforms/Scalar/Float2Int.cpp
@@ -359,9 +359,7 @@ bool Float2IntPass::validateAndTransform() {
// The number of bits required is the maximum of the upper and
// lower limits, plus one so it can be signed.
- unsigned MinBW = std::max(R.getLower().getSignificantBits(),
- R.getUpper().getSignificantBits()) +
- 1;
+ unsigned MinBW = R.getMinSignedBits() + 1;
LLVM_DEBUG(dbgs() << "F2I: MinBitwidth=" << MinBW << ", R: " << R << "\n");
// If we've run off the realms of the exactly representable integers,
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