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Fix for 127141 - Remove unneeded spilling around profiler hooks - #128731
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dhartglassMSFT
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On ARM64, only the lower halves of q8-q15 (128b) are callee save. LSRA spills upper halves of these into d8-d15 (64b subreg)
"UpperVectorSave" ref position tracks these around calls. LSRA currently just does this "upper-half-save-into-d8_d15" for all enregistered uppersave refs around calls.
Problem is
PROF_HOOKdoes NOT kill q0-q7. So we end up with more enregistered refs around a profiler hook than may be handled by d8-d15.Fix is that q0-q7 do not need their upper halves spilled around PROF_HOOK. I double checked with Noah that this is the case. And the asm stub does call out q0-q7 being preserved.
I was not able to recreate a repro, a profiled tail call taking v512 params seems to not be enough.
fixes #127141