On i386 we replace (add sp -4) with (push reg). This generates faster
and smaller code.
However, we are not copying RTX_FRAME_RELATED_P from the old
instructions to the new, and so we are not emitting unwind information
for the stack pointer adjustment. The breaks stack traces on gcj, and
I suspect it breaks a bunch of stuff elsewhere too.
This very crude patch sets RTX_FRAME_RELATED_P on every one of the new
instructions if any of the old instructions had RTX_FRAME_RELATED_P
set. It seems to do the trick, but I suspect there must be a more
subtle way to do it.
Can anyone suggest a neater way to do this?
Without this patch, for
java.lang.Throwable.Throwable(java.lang.String) we get
00a326a8 <java.lang.Throwable.Throwable(java.lang.String)>:
a326a8: 56 push %esi
a326a9: 53 push %ebx
a326aa: 50 push %eax <=== ** This is the insn generated by peephole **
a326ab: e8 00 00 00 00 call a326b0 <java.lang.Throwable.Throwable(java.lang.String)+0x8>
a326b0: 5b pop %ebx
00058f08 0000001c 0003252c FDE cie=000269e0 pc=00a328f8..00a3292e
Augmentation data: 00 00 00 00
DW_CFA_advance_loc: 1 to 00a328f9
DW_CFA_def_cfa_offset: 8
DW_CFA_advance_loc: 1 to 00a328fa
DW_CFA_def_cfa_offset: 12
DW_CFA_offset: r3 at cfa-12
DW_CFA_offset: r6 at cfa-8
DW_CFA_nop
after the patch, we get
0005946c 00000020 000328e4 FDE cie=00026b8c pc=00a326a8..00a326de
Augmentation data: 00 00 00 00
DW_CFA_advance_loc: 1 to 00a326a9
DW_CFA_def_cfa_offset: 8
DW_CFA_advance_loc: 1 to 00a326aa
DW_CFA_def_cfa_offset: 12
DW_CFA_advance_loc: 1 to 00a326ab
DW_CFA_def_cfa_offset: 16
DW_CFA_offset: r0 at cfa-16
DW_CFA_offset: r3 at cfa-12
DW_CFA_offset: r6 at cfa-8
Here's a trivial test case:
public class Hello {
public static void main(String[] args) {
System.out.println("Hello, World!");
new Throwable().printStackTrace();
}
}
$ ~/gcc/install/bin/gcj Hello.java --main=Hello -g
$ LD_LIBRARY_PATH=~/gcc/install/lib ./a.out
Hello, World!
java.lang.Throwable
at Hello.main (Hello.java:5)
Andrew.
2005-12-19 Andrew Haley <aph@xxxxxxxxxx>
* recog.c (peephole2_optimize): Copy RTX_FRAME_RELATED_P from old
instructions to new instructions.
Index: recog.c
===================================================================
--- recog.c (revision 108424)
+++ recog.c (working copy)
@@ -3107,6 +3107,7 @@
int match_len;
rtx note;
bool was_call = false;
+ bool frame_related = false;
/* Record this insn. */
if (--peep2_current < 0)
@@ -3122,6 +3123,14 @@
try = peephole2_insns (PATTERN (insn), insn, &match_len);
if (try != NULL)
{
+ {
+ rtx old_insn = insn;
+ for (i = 0; i <= match_len; ++i)
+ {
+ frame_related |= RTX_FRAME_RELATED_P (old_insn);
+ old_insn = NEXT_INSN (old_insn);
+ }
+ }
/* If we are splitting a CALL_INSN, look for the CALL_INSN
in SEQ and copy our CALL_INSN_FUNCTION_USAGE and other
cfg-related call notes. */
@@ -3179,6 +3188,16 @@
break;
}
+ if (frame_related)
+ {
+ rtx new_insn = try;
+ while (new_insn != NULL_RTX)
+ {
+ RTX_FRAME_RELATED_P (new_insn) = true;
+ new_insn = NEXT_INSN (new_insn);
+ }
+ }
+
i = match_len + peep2_current;
if (i >= MAX_INSNS_PER_PEEP2 + 1)
i -= MAX_INSNS_PER_PEEP2 + 1;
