[PATCH] D41895: [X86] Another attempt at support prefer-vector-width function attribute

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: lib/Target/X86/X86ISelLowering.cpp:16576-16578
+    // If we don't have VLX and we're trying to avoid 512-bit vectors we
+    // need special handling. Without VLX we have no choice but to use 512-bit
+    // vectors.
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echristo wrote:
> This comment could probably use some clarification: i.e. we're going to want to use blah blah blah.
> 
> Also how is this going to work for a preferred 128 bit vector?
128 bit vectors here would probably have to split several times using shuffles to move higher elements to the lower elements, then sign_extend_vector_inreg, testd, and concat the results.


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Comment at: lib/Target/X86/X86TargetMachine.cpp:263
+  unsigned PreferVectorWidthOverride = 0;
+  if (F.hasFnAttribute("prefer-vector-width")) {
+    StringRef Val = F.getFnAttribute("prefer-vector-width").getValueAsString();
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echristo wrote:
> Bikeshed: "preferred-vector-width"?
It got named this way because gcc implemented their command line option as -mprefer-vector-width=  so then I matched that in clang and kept the attribute name matching the command line option.


https://reviews.llvm.org/D41895