Fix PR rtl-optimization/100411

This is the bootstrap failure of GCC 11 on MinGW64 configured with --enable-
tune=nocona.  The bottom line is that SEH does not support CFI for epilogues
but the x86 back-end nevertheless attaches it to instructions, so we have to
filter it out and this is done by detecting the end of the prologue by means
of the NOTE_INSN_PROLOGUE_END note.

But the compiler manages to generate a second epilogue before this note in
the RTL stream and this fools the aforementioned logic.  The root cause is
cross-jumping, which inserts a jump before the end of the prologue, in fact
just before the note; the rest (CFG cleanup, BB reordering, etc) is downhill
from there.

gcc/
	PR rtl-optimization/100411
	* cfgcleanup.c (try_crossjump_to_edge): Also skip end of prologue
	and beginning of function markers.

diff --git a/gcc/cfgcleanup.c b/gcc/cfgcleanup.c
index f05cb61..17edc4f 100644 (file)
--- a/gcc/cfgcleanup.c
+++ b/gcc/cfgcleanup.c
@@ -2145,7 +2145,11 @@ try_crossjump_to_edge (int mode, edge e1, edge e2,
   if (NOTE_INSN_BASIC_BLOCK_P (newpos1))
     newpos1 = NEXT_INSN (newpos1);
 
-  while (DEBUG_INSN_P (newpos1))
+  /* Skip also prologue and function markers.  */
+  while (DEBUG_INSN_P (newpos1)
+        || (NOTE_P (newpos1)
+            && (NOTE_KIND (newpos1) == NOTE_INSN_PROLOGUE_END
+                || NOTE_KIND (newpos1) == NOTE_INSN_FUNCTION_BEG)))
     newpos1 = NEXT_INSN (newpos1);
 
   redirect_from = split_block (src1, PREV_INSN (newpos1))->src;