https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92190
--- Comment #10 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> --- (In reply to Uroš Bizjak from comment #8) > (In reply to Liu Hao from comment #7) > > MSDN says 'the upper portions of YMM0-15 and ZMM0-15 are considered volatile > > and must be considered destroyed on function calls' explicitly [1]. > > > > I am not clear about the cause of OP's ICE, but I think it should conform to > > MSABI to emit VZEROUPPER in the epilog, followed by restoring XMM6 - XMM15, > > destroying their upper halves. Similar with the prolog. > > The insertion of vzeroupper is not "invisible" to stack frame management > code any more, since vzeroupper is now defined as: > > (insn 738 619 434 2 (parallel [ > (unspec_volatile [ > (const_int 0 [0]) > ] UNSPECV_VZEROUPPER) > (clobber (reg:V2DI 20 xmm0)) > (clobber (reg:V2DI 21 xmm1)) > (clobber (reg:V2DI 22 xmm2)) > (clobber (reg:V2DI 23 xmm3)) > (clobber (reg:V2DI 24 xmm4)) > (clobber (reg:V2DI 25 xmm5)) > (set (reg:V2DI 26 xmm6) > (reg:V2DI 26 xmm6)) > (clobber (reg:V2DI 27 xmm7)) > (clobber (reg:V2DI 44 xmm8)) > (clobber (reg:V2DI 45 xmm9)) > (clobber (reg:V2DI 46 xmm10)) > (clobber (reg:V2DI 47 xmm11)) > (clobber (reg:V2DI 48 xmm12)) > (clobber (reg:V2DI 49 xmm13)) > (clobber (reg:V2DI 50 xmm14)) > (clobber (reg:V2DI 51 xmm15)) > ]) "pr92190.c":8:3 -1 > (nil)) > > > . The insertion point of vzeroupper pass is just after reload pass, and now > all xmm registers (xmm0 - xmm15) become live. This is not a problem in SYSV > ABI, where all registers are call_used, but in MS ABI, the prologue now > tries to save xmm6 - xmm15 to the stack. > > So, vzeroupper should be described in a way that won't trigger saves of xmm6 > - xmm15 to the stack, while still mark that high part of the register is > clobbered. Ah, OK. It should be safe to leave out a clobber if !df_regs_ever_live_p and if we're guaranteed not to introduce new references to the register later.
