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| author | Sanjay Patel <spatel@rotateright.com> | 2021-06-03 13:15:23 -0400 |
|---|---|---|
| committer | Sanjay Patel <spatel@rotateright.com> | 2021-06-03 13:58:19 -0400 |
| commit | b865eead76577b031c6fae5e2490e7be0073f201 (patch) | |
| tree | 23e058752ec4247671ce94af673e2b6185dd1a37 /llvm/lib/Support/Signposts.cpp | |
| parent | 3e55f55048387a8efef01e445d46fc5cf100285d (diff) | |
| download | llvm-b865eead76577b031c6fae5e2490e7be0073f201.zip llvm-b865eead76577b031c6fae5e2490e7be0073f201.tar.gz llvm-b865eead76577b031c6fae5e2490e7be0073f201.tar.bz2 | |
[InstCombine] eliminate sext and/or trunc if value has enough signbits
If we have enough signbits in a source value, we can skip an
intermediate cast for a trunc+sext pair:
https://alive2.llvm.org/ce/z/A_mQt-
This is the original problem shown in:
https://llvm.org/PR49543
There's a test that shows we transformed what used to be
a pair of shifts, so that suggests we could add another
ComputeNumSignBits fold starting from a shift.
There does not appear to be any change in compile-time
from the extra analysis:
https://llvm-compile-time-tracker.com/compare.php?from=3d2c9069dcafd0cbb641841aa3dd6e851fb7d760&to=b9513cdf2419704c7bb0c3a02a9ca06aae13d902&stat=instructions
Differential Revision: https://reviews.llvm.org/D103617
Diffstat (limited to 'llvm/lib/Support/Signposts.cpp')
0 files changed, 0 insertions, 0 deletions