I don't see a reason to add this new function. I would just inline it
into noce_can_store_speculate_p, replacing the call to
memory_modified_in_p. And I'm not sure I see a reason to change the
comment for memory_modified_in_p, it seems to already be accurate.
My comment was just clearer to me, but probably because I wrote it :).
I have revert it.
Clearly we could consider the possibility of a PARALLEL of SET insns,
but of course most the compiler won't handle that anyhow. I suppose
that would be a reason to use memory_surely_modified_in_insn_p, but in
that case you might as well handle the PARALLEL case now.
Done. Is this what you had in mind?
Tested on x86-64 Linux by looking at the generated assembly for the
testcase with a dominating write and without. Bootstrap and regtested
as well.
PR rtl-optimization/54900
* ifcvt.c (noce_can_store_speculate_p): Call
memory_surely_modified_in_insn_p.
* alias.c (memory_surely_modified_in_insn_p): New.
(set_dest_equal_p): New.
diff --git a/gcc/alias.c b/gcc/alias.c
index 0c6a744..f28e9a6 100644
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -2760,6 +2760,39 @@ memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
return memory_modified;
}
+/* Return TRUE if the destination of a set is rtx identical to
+ ITEM. */
+static inline bool
+set_dest_equal_p (const_rtx set, const_rtx item)
+{
+ rtx dest = SET_DEST (set);
+ return rtx_equal_p (dest, item);
+}
+
+/* Like memory_modified_in_insn_p, but return TRUE if INSN will
+ *SURELY* modify the memory contents of MEM. */
+bool
+memory_surely_modified_in_insn_p (const_rtx mem, const_rtx insn)
+{
+ if (!INSN_P (insn))
+ return false;
+ insn = PATTERN (insn);
+ if (GET_CODE (insn) == SET)
+ return set_dest_equal_p (insn, mem);
+ else if (GET_CODE (insn) == PARALLEL)
+ {
+ int i;
+ for (i = 0; i < XVECLEN (insn, 0); i++)
+ {
+ rtx sub = XVECEXP (insn, 0, i);
+ if (GET_CODE (sub) == SET
+ && set_dest_equal_p (sub, mem))
+ return true;
+ }
+ }
+ return false;
+}
+
/* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
array. */
diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index 2f486a2..659e464 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -2415,7 +2415,7 @@ noce_can_store_speculate_p (basic_block top_bb, const_rtx
mem)
|| (CALL_P (insn) && (!RTL_CONST_CALL_P (insn)))))
return false;
- if (memory_modified_in_insn_p (mem, insn))
+ if (memory_surely_modified_in_insn_p (mem, insn))
return true;
if (modified_in_p (XEXP (mem, 0), insn))
return false;
diff --git a/gcc/rtl.h b/gcc/rtl.h
index cd5d435..d449ee1 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -2614,6 +2614,7 @@ extern void init_alias_analysis (void);
extern void end_alias_analysis (void);
extern void vt_equate_reg_base_value (const_rtx, const_rtx);
extern bool memory_modified_in_insn_p (const_rtx, const_rtx);
+extern bool memory_surely_modified_in_insn_p (const_rtx, const_rtx);
extern bool may_be_sp_based_p (rtx);
extern rtx gen_hard_reg_clobber (enum machine_mode, unsigned int);
extern rtx get_reg_known_value (unsigned int);
