[PATCH] D39575: [X86] Add subtarget features prefer-avx256 and prefer-avx128 and use them to limit vector width presented by TTI

[David Kreitzer via Phabricator via llvm-commits]

DavidKreitzer added a comment.

This looks reasonable to me, Craig. For testing, the obvious thing would be to test the effect on the LoopVectorizer, since it is the primary consumer of this information.



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Comment at: lib/Target/X86/X86Subtarget.h:64
+  enum X86PreferVecWidthEnum {
+    // NOTE: Strictest constraint must have highest encoding.
+    PreferAny, Prefer256, Prefer128
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It might be worth expanding upon this a bit to make is clear why Prefer128 is "stricter" than Prefer256.

I have no objection to this choice of ordering, but it does make the code at lines 535-539 read a little funny.


https://reviews.llvm.org/D39575