i386: Don't use insvti_{high,low}part with -O0 (for compile-time).

This patch attempts to help with PR rtl-optimization/110587, a regression
of -O0 compile time for the pathological pr28071.c.  My recent patch helps
a bit, but hasn't returned -O0 compile-time to where it was before my
ix86_expand_move changes.  The obvious solution/workaround is to guard
these new TImode parameter passing optimizations with "&& optimize", so
they don't trigger when compiling with -O0.  The very minor complication
is that "&& optimize" alone leads to the regression of pr110533.c, where
our improved TImode parameter passing fixes a wrong-code issue with naked
functions, importantly, when compiling with -O0.  This should explain
the one line fix below "&& (optimize || ix86_function_naked (cfun))".

I've an additional fix/tweak or two for this compile-time issue, but
this change eliminates the part of the regression that I've caused.

2023-07-22  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/i386/i386-expand.cc (ix86_expand_move): Disable the
	64-bit insertions into TImode optimizations with -O0, unless
	the function has the "naked" attribute (for PR target/110533).

diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index a5c000f366d9a73a4e7e4be6ac7f5dcad6f31681..042190982557f5b80b0554ad1a68ca36098d57be 100644 (file)
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -544,6 +544,8 @@ ix86_expand_move (machine_mode mode, rtx operands[])
 
   /* Special case inserting 64-bit values into a TImode register.  */
   if (TARGET_64BIT
+      /* Disable for -O0 (see PR110587) unless naked (PR110533).  */
+      && (optimize || ix86_function_naked (current_function_decl))
       && (mode == DImode || mode == DFmode)
       && SUBREG_P (op0)
       && GET_MODE (SUBREG_REG (op0)) == TImode