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Restore RTL alias analysis for hard frame pointer

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The change:

	2021-07-28  Bin Cheng  <bin.cheng@linux.alibaba.com>

	alias.c (init_alias_analysis): Don't skip prologue/epilogue.

broke the alias analysis for the hard frame pointer (when it is used as a
frame pointer, i.e. when the frame pointer is not eliminated) described in
the large comment at the top of the file, because static_reg_base_value is
set for it and, consequently, new_reg_base_value too.

When the instruction saving the stack pointer into the hard frame pointer in
the prologue is processed, it is viewed as a second set of the hard frame
pointer and to a different value by record_set, which then proceeds to reset
new_reg_base_value to 0 and the game is over.

gcc/
	* alias.cc (init_alias_analysis): Do not record sets to the hard
	frame pointer if the frame pointer has not been eliminated.
This commit is contained in:
Eric Botcazou 2022-10-29 10:16:18 +02:00
parent 7e7ebe3e35
commit 96ba0c369e
1 changed files with 12 additions and 7 deletions
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19
gcc/alias.cc
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@ -3369,6 +3369,10 @@ memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
void
init_alias_analysis (void)
{
const bool frame_pointer_eliminated
= reload_completed
&& !frame_pointer_needed
&& targetm.can_eliminate (FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM);
unsigned int maxreg = max_reg_num ();
int changed, pass;
int i;
@ -3446,12 +3450,8 @@ init_alias_analysis (void)
for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
if (static_reg_base_value[i]
/* Don't treat the hard frame pointer as special if we
eliminated the frame pointer to the stack pointer instead. */
&& !(i == HARD_FRAME_POINTER_REGNUM
&& reload_completed
&& !frame_pointer_needed
&& targetm.can_eliminate (FRAME_POINTER_REGNUM,
STACK_POINTER_REGNUM)))
eliminated the frame pointer to the stack pointer. */
&& !(i == HARD_FRAME_POINTER_REGNUM && frame_pointer_eliminated))
{
new_reg_base_value[i] = static_reg_base_value[i];
bitmap_set_bit (reg_seen, i);
@ -3467,10 +3467,15 @@ init_alias_analysis (void)
{
rtx note, set;
/* Treat the hard frame pointer as special unless we
eliminated the frame pointer to the stack pointer. */
if (!frame_pointer_eliminated
&& modified_in_p (hard_frame_pointer_rtx, insn))
continue;
/* If this insn has a noalias note, process it, Otherwise,
scan for sets. A simple set will have no side effects
which could change the base value of any other register. */
if (GET_CODE (PATTERN (insn)) == SET
&& REG_NOTES (insn) != 0
&& find_reg_note (insn, REG_NOALIAS, NULL_RTX))