[PATCH] D32002: [X86] Improve large struct pass by value performance

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

Is this related to this bit from the Intel Optimization Manual.

3.7.7 Enhanced REP MOVSB and STOSB operation (ERMSB)
Beginning with processors based on Intel microarchitecture code named Ivy Bridge,
REP string operation using MOVSB and STOSB can provide both flexible and highperformance
REP string operations for software in common situations like memory
copy and set operations. Processors that provide enhanced MOVSB/STOSB operations
are enumerated by the CPUID feature flag: CPUID:(EAX=7H,
ECX=0H):EBX.ERMSB[bit 9] = 1.


https://reviews.llvm.org/D32002