Hi!
The following testcase ICEs on x86_64-linux since df_note_add_problem ()
call has been added to mode switching.
The problem is that the pro_and_epilogue pass in
prepare_shrink_wrap -> copyprop_hardreg_forward_bb_without_debug_insn
uses regcprop.cc infrastructure which relies on accurate REG_DEAD/REG_UNUSED
notes. E.g. regcprop.cc
/* We need accurate notes. Earlier passes such as if-conversion may
leave notes in an inconsistent state. */
df_note_add_problem ();
documents that. On the testcase below it is in particular the
/* Detect obviously dead sets (via REG_UNUSED notes) and remove them. */
if (set
&& !RTX_FRAME_RELATED_P (insn)
&& NONJUMP_INSN_P (insn)
&& !may_trap_p (set)
&& find_reg_note (insn, REG_UNUSED, SET_DEST (set))
&& !side_effects_p (SET_SRC (set))
&& !side_effects_p (SET_DEST (set)))
{
bool last = insn == BB_END (bb);
delete_insn (insn);
if (last)
break;
continue;
}
case where a stale REG_UNUSED note breaks stuff up (added in vzeroupper
pass, redundant insn after it deleted later).
The following patch makes sure the notes are not stale if shrink wrapping
is enabled.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2023-12-02 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/112760
* function.cc (thread_prologue_and_epilogue_insns): If
SHRINK_WRAPPING_ENABLED, call df_note_add_problem before calling
df_analyze.
* gcc.dg/pr112760.c: New test.
--- gcc/function.cc.jj 2023-11-07 08:32:01.699254744 +0100
+++ gcc/function.cc 2023-12-01 13:42:51.885189341 +0100
@@ -6036,6 +6036,11 @@ make_epilogue_seq (void)
void
thread_prologue_and_epilogue_insns (void)
{
+ /* prepare_shrink_wrap uses copyprop_hardreg_forward_bb_without_debug_insn
+ which uses regcprop.cc functions which rely on accurate REG_UNUSED
+ and REG_DEAD notes. */
+ if (SHRINK_WRAPPING_ENABLED)
+ df_note_add_problem ();
df_analyze ();
/* Can't deal with multiple successors of the entry block at the
--- gcc/testsuite/gcc.dg/pr112760.c.jj 2023-12-01 13:46:57.444746529 +0100
+++ gcc/testsuite/gcc.dg/pr112760.c 2023-12-01 13:46:36.729036971 +0100
@@ -0,0 +1,22 @@
+/* PR rtl-optimization/112760 */
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-dce -fno-guess-branch-probability
--param=max-cse-insns=0" } */
+/* { dg-additional-options "-m8bit-idiv -mavx" { target i?86-*-* x86_64-*-* }
} */
+
+unsigned g;
+
+__attribute__((__noipa__)) unsigned short
+foo (unsigned short a, unsigned short b)
+{
+ unsigned short x = __builtin_add_overflow_p (a, g, (unsigned short) 0);
+ g -= g / b;
+ return x;
+}
+
+int
+main ()
+{
+ unsigned short x = foo (40, 6);
+ if (x != 0)
+ __builtin_abort ();
+}
Jakub
