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

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).