[all-commits] [llvm/llvm-project] d9e1f9: [InstCombine] Fold icmp of truncated left shift
Sanjay Patel via All-commits
all-commits at lists.llvm.org
Thu Sep 8 07:50:02 PDT 2022
Branch: refs/heads/main
Home: https://github.com/llvm/llvm-project
Commit: d9e1f9d7591b0d3e4df3c0e33ffd8984fb1632a5
https://github.com/llvm/llvm-project/commit/d9e1f9d7591b0d3e4df3c0e33ffd8984fb1632a5
Author: Sanjay Patel <spatel at rotateright.com>
Date: 2022-09-08 (Thu, 08 Sep 2022)
Changed paths:
M llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
M llvm/test/Transforms/InstCombine/icmp-trunc.ll
Log Message:
-----------
[InstCombine] Fold icmp of truncated left shift
(trunc (1 << Y) to iN) == 0 --> Y u>= N
(trunc (1 << Y) to iN) != 0 --> Y u< N
These can be generalized in several ways as noted by the TODO
items, but this handles the pattern in the motivating bug report.
Fixes #51889
Differential Revision: https://reviews.llvm.org/D115480
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