[PATCH] D61472: [X86FixupLEAs] Turn optIncDec into a generic two address LEA optimizer. Support LEA64_32r properly.

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

I haven't looked closely at the series of transforms that gets us here, so let me ask: would it be more efficient to produce the add/inc/dec machine instructions directly rather than LEA? Or do we do this because the 3-address opportunity helps register allocation, so this late reversal is a special-case of the more generally useful transforms that produce LEA in the 1st place?



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Comment at: llvm/lib/Target/X86/X86FixupLEAs.cpp:11
 // re-written as LEA instructions in order to reduce pipeline delays.
 // When optimizing for size it replaces suitable LEAs with INC or DEC.
 //
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Should update this comment to better match the logic:
"It replaces LEAs with ADD/INC/DEC when that is better for size/speed." ?


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