| Issue |
81755
|
| Summary |
[X86] Use __builtin_readsteadycounter to access MPERF counter (and APERF equivalent(
|
| Labels |
backend:X86
|
| Assignees |
|
| Reporter |
RKSimon
|
#81331 added support for a `__builtin_readsteadycounter` intrinsic which returns a fixed frequency clock counter. It returns 0 on failure.
x86 can use this as a wrapper to read the MPERF counter - on Intel (and default) I think this will need to lower to a libcall, but on AMD znver2 (or later) we can use the RDPRU instruction.
Ideally we need a companion `__builtin_readvariablecounter` intrinsic which returns the APERF counter to calculate the effective cpu frequency (we can't use `__builtin_readcyclecounter` as that returns RDTSC which is a different time scale).
![]()
_______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
