On 10/06/11 17:57, Ian Lance Taylor wrote:
> There is absolutely no reason to try to shrink wrap that code. It will
> never help. That code always has to be first. It especially has to be
> first because the gold linker recognizes the prologue specially when a
> split-stack function calls a non-split-stack function, in order to
> request a larger stack.
Urgh, ok.
> Therefore, it seems to me that we should apply shrink wrapping to the
> function as it exists *before* the split-stack prologue is created. The
> flag_split_stack bit should be moved after the flag_shrink_wrap bit.
Sounds like we just need to always emit the split prologue on the
original entry edge then. Can you test the following with Go?
Bernd
* function.c (thread_prologue_and_epilogue_insns): Emit split
prologue on the orig_entry_edge. Don't account for it in
prologue_clobbered.
Index: gcc/function.c
===================================================================
--- gcc/function.c (revision 179619)
+++ gcc/function.c (working copy)
@@ -5602,10 +5602,6 @@ thread_prologue_and_epilogue_insns (void
note_stores (PATTERN (p_insn), record_hard_reg_sets,
&prologue_clobbered);
}
- for (p_insn = split_prologue_seq; p_insn; p_insn = NEXT_INSN (p_insn))
- if (NONDEBUG_INSN_P (p_insn))
- note_stores (PATTERN (p_insn), record_hard_reg_sets,
- &prologue_clobbered);
bitmap_initialize (&bb_antic_flags, &bitmap_default_obstack);
bitmap_initialize (&bb_on_list, &bitmap_default_obstack);
@@ -5758,7 +5754,7 @@ thread_prologue_and_epilogue_insns (void
if (split_prologue_seq != NULL_RTX)
{
- insert_insn_on_edge (split_prologue_seq, entry_edge);
+ insert_insn_on_edge (split_prologue_seq, orig_entry_edge);
inserted = true;
}
if (prologue_seq != NULL_RTX)
