My mistake yesterday. I thought I'd tested both x86_64 -m64/-m32, but not so.
Anyway, as the comment says, the backend keeps querying the static chain, and
if you don't early out, it sets ix86_static_chain_on_stack, at which point the
setting is permanent and affects prologue generation, and not in a good way.
Tested i686-linux and committed.
r~
PR target/63977
* config/i386/i386.c (ix86_static_chain): Reinstate the check
for DECL_STATIC_CHAIN.
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index fffddfc..6c8dbd6 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -27360,6 +27360,12 @@ ix86_static_chain (const_tree fndecl_or_type, bool
incoming_p)
{
unsigned regno;
+ /* While this function won't be called by the middle-end when a static
+ chain isn't needed, it's also used throughout the backend so it's
+ easiest to keep this check centralized. */
+ if (DECL_P (fndecl_or_type) && !DECL_STATIC_CHAIN (fndecl_or_type))
+ return NULL;
+
if (TARGET_64BIT)
{
/* We always use R10 in 64-bit mode. */
