Matt Arsenault 42098c4a30 GlobalISel: Fix legalization error where CSE leaves behind dead defs ... If the conversion artifact introduced in the unmerge of cast of merge combine already existed in the function, this would introduce dead copies which kept the old casts around, neither of which were deleted, and would fail legalization. This would fail as follows: The G_UNMERGE_VALUES of the G_SEXT of the G_BUILD_VECTOR would introduce a G_SEXT for each of the scalars. Some of the required G_SEXTs already existed in the function, so CSE moves them up in the function and introduces a copy to the original result register. The introduced CSE copies are dead, since the originally G_SEXTs were already directly used. These copies add a use to the illegal G_SEXTs, so they are not deleted. The artifact combiner does not see the defs that need to be updated, since it was hidden inside the CSE builder. I see 2 potential fixes, and opted for the mechanically simpler one, which is to just not insert the cast if the result operand isn't used. Alternatively, we could not insert the cast directly into the result register, and use replaceRegOrBuildCopy similar to the case where there is no conversion. I suspect this is a wider problem in the artifact combiner.		2022-01-18 17:04:40 -05:00
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llvm	GlobalISel: Fix legalization error where CSE leaves behind dead defs	2022-01-18 17:04:40 -05:00
llvm-c	[clang][CodeGen] Remove the signed version of createExpression	2021-12-27 14:16:08 +08:00