gimple-fold: Avoid ICEs with bogus declarations like const attribute no snprintf...

gimple-fold: Avoid ICEs with bogus declarations like const attribute no snprintf [PR117358]

When one puts incorrect const or pure attributes on declarations of various
C APIs which have corresponding builtins (vs. what they actually do), we can
get tons of ICEs in gimple-fold.cc.

The following patch fixes it by giving up gimple_fold_builtin_* folding
if the functions don't have gimple_vdef (or for pure functions like
bcmp/strchr/strstr gimple_vuse) when in SSA form (during gimplification
they will surely have both of those NULL even when declared correctly,
yet it is highly desirable to fold them).

Or shall I replace
!gimple_vdef (stmt) && gimple_in_ssa_p (cfun)
tests with
(gimple_call_flags (stmt) & (ECF_CONST | ECF_PURE | ECF_NOVOPS)) != 0
and
!gimple_vuse (stmt) && gimple_in_ssa_p (cfun)
with
(gimple_call_flags (stmt) & (ECF_CONST | ECF_NOVOPS)) != 0
?

2024-11-28  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/117358
	* gimple-fold.cc (gimple_fold_builtin_memory_op): Punt if stmt has no
	vdef in ssa form.
	(gimple_fold_builtin_bcmp): Punt if stmt has no vuse in ssa form.
	(gimple_fold_builtin_bcopy): Punt if stmt has no vdef in ssa form.
	(gimple_fold_builtin_bzero): Likewise.
	(gimple_fold_builtin_memset): Likewise.  Use return false instead of
	return NULL_TREE.
	(gimple_fold_builtin_strcpy): Punt if stmt has no vdef in ssa form.
	(gimple_fold_builtin_strncpy): Likewise.
	(gimple_fold_builtin_strchr): Punt if stmt has no vuse in ssa form.
	(gimple_fold_builtin_strstr): Likewise.
	(gimple_fold_builtin_strcat): Punt if stmt has no vdef in ssa form.
	(gimple_fold_builtin_strcat_chk): Likewise.
	(gimple_fold_builtin_strncat): Likewise.
	(gimple_fold_builtin_strncat_chk): Likewise.
	(gimple_fold_builtin_string_compare): Likewise.
	(gimple_fold_builtin_fputs): Likewise.
	(gimple_fold_builtin_memory_chk): Likewise.
	(gimple_fold_builtin_stxcpy_chk): Likewise.
	(gimple_fold_builtin_stxncpy_chk): Likewise.
	(gimple_fold_builtin_stpcpy): Likewise.
	(gimple_fold_builtin_snprintf_chk): Likewise.
	(gimple_fold_builtin_sprintf_chk): Likewise.
	(gimple_fold_builtin_sprintf): Likewise.
	(gimple_fold_builtin_snprintf): Likewise.
	(gimple_fold_builtin_fprintf): Likewise.
	(gimple_fold_builtin_printf): Likewise.
	(gimple_fold_builtin_realloc): Likewise.

	* gcc.c-torture/compile/pr117358.c: New test.

(cherry picked from commit 29032dfa57629d1713a97b17a785273823993a91)