Re: [PATCH] x86: Update previous scratch register check in LCP stall peepholes

[Uros Bizjak]

On Wed, Jun 24, 2026 at 8:07 AM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> Use the previous scratch register if it is a general purpose register
> wide enough to supply the required mode, or an SSE register which
> is valid in the required mode.  If the required mode is QImode, the
> previous scratch register must be valid in QImode.  Also match const0_rtx
> against CONST0_RTX.
>
> gcc/
>
> PR target/125958
> * config/i386/i386-expand.cc (ix86_expand_lcp_stall_peephole):
> Update previous scratch register check.  Match const0_rtx
> against CONST0_RTX.
>
> gcc/testsuite/
>
> PR target/125958
> * gcc.target/i386/pr125958a.c: New test.
> * gcc.target/i386/pr125958b.c: Likewise.

-  /* Reject DEST if a register is not wide enough to
-     supply MODE or invalid for QImode.  */
-  if (!REG_P (dest)
-      || (GET_MODE_SIZE (GET_MODE (dest))
-  < GET_MODE_SIZE (mode))
-      || (mode == QImode
-  && !ANY_QI_REGNO_P (REGNO (dest))))
+  /* Reject DEST if it isn't a general purpose register
+     wide enough to supply MODE or invalid for QImode
+     or isn't an SSE register which is invalid for
+     MODE.  */
+  if ((!GENERAL_REG_P (dest)

Just change !REG_P (dest) to !GENERAL_REG_P (dest) and don't bother
with SSE regs.

Uros.