Yingwei Zheng 6681650025 [InstCombine] Revert the signed icmp -> unsigned icmp canonicalization when folding icmp Pred min|max(X, Y), Z (#76685) ...

This patch tries to flip the signedness of predicates when folding an
unsigned icmp with a signed min/max. It will enable more optimizations
as we canonicalizes a signed icmp into an unsigned icmp when both
operands are known to have the same sign.
Fixes #76672.

Compile-time impact:
http://llvm-compile-time-tracker.com/compare.php?from=949ec83eaf6fa6dbffb94c2ea9c0a4d5efdbd239&to=2deca1aea8a4e13609bab72c522a97d424f0fc2d&stat=instructions:u


|stage1-O3|stage1-ReleaseThinLTO|stage1-ReleaseLTO-g|stage1-O0-g|stage2-O3|stage2-O0-g|stage2-clang|
|--|--|--|--|--|--|--|
|-0.00%|+0.01%|+0.05%|-0.12%|-0.01%|-0.03%|-0.00%|

NOTE: We can flip the signedness of predicate if both operands are
negative. But I don't see the benefit of handling these cases.

2024-01-05 14:39:16 +08:00

11 KiB

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