Hi! On Tue, Feb 04, 2020 at 11:16:06AM +0100, Uros Bizjak wrote: > I guess that Comment #9 patch form the PR should be trivially correct, > but althouhg it looks obvious, I don't want to propose the patch since > I have no means of testing it.
I don't have means of testing it either. https://docs.microsoft.com/en-us/cpp/build/x64-calling-convention?view=vs-2019 is quite explicit that [xyz]mm16-31 are call clobbered and only xmm6-15 (low 128-bits only) are call preserved. Jonathan, could you please test this if it is sufficient to just change CALL_USED_REGISTERS or if e.g. something in the pro/epilogue needs tweaking too? Thanks. We are talking e.g. about /* { dg-options "-O2 -mabi=ms -mavx512vl" } */ typedef double V __attribute__((vector_size (16))); void foo (void); V bar (void); void baz (V); void qux (void) { V c; { register V a __asm ("xmm18"); V b = bar (); asm ("" : "=x" (a) : "0" (b)); c = a; } foo (); { register V d __asm ("xmm18"); V e; d = c; asm ("" : "=x" (e) : "0" (d)); baz (e); } } where according to the MSDN doc gcc incorrectly holds the c value in xmm18 register across the foo call; if foo is compiled by some Microsoft compiler (or LLVM), then it could clobber %xmm18. If all xmm18 occurrences are changed to say xmm15, then it is valid to hold the 128-bit value across the foo call (though, surprisingly, LLVM saves it into stack anyway). 2020-02-04 Uroš Bizjak <ubiz...@gmail.com> * config/i386/config/i386/i386.h (CALL_USED_REGISTERS): Make xmm16-xmm31 call-used even in 64-bit ms-abi. --- gcc/config/i386/config/i386/i386.h.jj 2020-01-22 10:19:24.199221986 +0100 +++ gcc/config/i386/config/i386/i386.h 2020-02-04 12:09:12.338341003 +0100 @@ -1128,9 +1128,9 @@ extern const char *host_detect_local_cpu /*xmm8,xmm9,xmm10,xmm11,xmm12,xmm13,xmm14,xmm15*/ \ 6, 6, 6, 6, 6, 6, 6, 6, \ /*xmm16,xmm17,xmm18,xmm19,xmm20,xmm21,xmm22,xmm23*/ \ - 6, 6, 6, 6, 6, 6, 6, 6, \ + 1, 1, 1, 1, 1, 1, 1, 1, \ /*xmm24,xmm25,xmm26,xmm27,xmm28,xmm29,xmm30,xmm31*/ \ - 6, 6, 6, 6, 6, 6, 6, 6, \ + 1, 1, 1, 1, 1, 1, 1, 1, \ /* k0, k1, k2, k3, k4, k5, k6, k7*/ \ 1, 1, 1, 1, 1, 1, 1, 1 } Jakub
