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[X86] Enable isel to use the PAUSE instruction even when SSE2 is disabled. Clang part

Authored by craig.topper on Aug 5 2017, 11:41 AM.



On older processors this instruction encoding is treated as a NOP.

MSVC doesn't disable intrinsics based on features the way clang/gcc does. Because the PAUSE instruction encoding doesn't crash older processors, some software out there uses these intrinsics without checking for SSE2.

This change also seems to also be consistent with gcc behavior.

Fixes PR34079

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Event Timeline

craig.topper created this revision.Aug 5 2017, 11:41 AM
craig.topper edited the summary of this revision. (Show Details)
RKSimon edited edge metadata.Aug 5 2017, 12:11 PM

Codegen test case on no-sse2 target?

Add test case

RKSimon accepted this revision.Aug 5 2017, 3:03 PM


This revision is now accepted and ready to land.Aug 5 2017, 3:03 PM
This revision was automatically updated to reflect the committed changes.