> -----Original Message-----
> From: Richard Henderson [mailto:r...@redhat.com]
> Sent: Friday, November 21, 2014 2:27 AM
> To: Zhenqiang Chen; gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH, ifcvt] Fix PR63917
>
> On 11/20/2014 10:48 AM, Zhenqiang Chen wrote:
> > +/* Check X clobber CC reg or not. */
> > +
> > +static bool
> > +clobber_cc_p (rtx x)
> > +{
> > + RTX_CODE code = GET_CODE (x);
> > + int i;
> > +
> > + if (code == CLOBBER
> > + && REG_P (XEXP (x, 0))
> > + && (GET_MODE_CLASS (GET_MODE (XEXP (x, 0))) == MODE_CC))
> > + return TRUE;
> > + else if (code == PARALLEL)
> > + for (i = 0; i < XVECLEN (x, 0); i++)
> > + if (clobber_cc_p (XVECEXP (x, 0, i)))
> > + return TRUE;
> > + return FALSE;
> > +}
>
> Why would you need something like this when modified_between_p or one
> of its kin ought to do the job?
Thanks for the comments. Patch is updated to use set_of.
And it is also enhanced to make sure that the new generated insns can not
clobber CC.
Bootstrap and no make check regression on X86-64 and IA32.
OK for trunk?
Thanks!
-Zhenqiang
ChangeLog:
2014-11-24 Zhenqiang Chen <zhenqiang.c...@arm.com>
PR rtl-optimization/63917
* ifcvt.c (cc_in_cond): New function.
(end_ifcvt_sequence): Make sure new generated insns do not clobber
CC.
(noce_process_if_block, check_cond_move_block): Check CC references.
testsuite/ChangeLog:
2014-11-24 Zhenqiang Chen <zhenqiang.c...@arm.com>
* gcc.dg/pr63917.c: New test.
diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index 21f08c2..1acd0ff 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -1016,6 +1016,18 @@ noce_emit_move_insn (rtx x, rtx y)
0, 0, outmode, y);
}
+/* Return the CC reg if it is used in COND. */
+
+static rtx
+cc_in_cond (rtx cond)
+{
+ if ((HAVE_cbranchcc4) && cond
+ && (GET_MODE_CLASS (GET_MODE (XEXP (cond, 0))) == MODE_CC))
+ return XEXP (cond, 0);
+
+ return NULL_RTX;
+}
+
/* Return sequence of instructions generated by if conversion. This
function calls end_sequence() to end the current stream, ensures
that are instructions are unshared, recognizable non-jump insns.
@@ -1026,6 +1038,7 @@ end_ifcvt_sequence (struct noce_if_info *if_info)
{
rtx_insn *insn;
rtx_insn *seq = get_insns ();
+ rtx cc = cc_in_cond (if_info->cond);
set_used_flags (if_info->x);
set_used_flags (if_info->cond);
@@ -1040,7 +1053,9 @@ end_ifcvt_sequence (struct noce_if_info *if_info)
allows proper placement of required clobbers. */
for (insn = seq; insn; insn = NEXT_INSN (insn))
if (JUMP_P (insn)
- || recog_memoized (insn) == -1)
+ || recog_memoized (insn) == -1
+ /* Make sure new generated code does not clobber CC. */
+ || (cc && set_of (cc, insn)))
return NULL;
return seq;
@@ -2544,6 +2559,7 @@ noce_process_if_block (struct noce_if_info *if_info)
rtx_insn *insn_a, *insn_b;
rtx set_a, set_b;
rtx orig_x, x, a, b;
+ rtx cc;
/* We're looking for patterns of the form
@@ -2655,6 +2671,13 @@ noce_process_if_block (struct noce_if_info *if_info)
if_info->a = a;
if_info->b = b;
+ /* Skip it if the instruction to be moved might clobber CC. */
+ cc = cc_in_cond (cond);
+ if (cc)
+ if (set_of (cc, insn_a)
+ || (insn_b && set_of (XEXP (cond, 0), insn_b)))
+ return FALSE;
+
/* Try optimizations in some approximation of a useful order. */
/* ??? Should first look to see if X is live incoming at all. If it
isn't, we don't need anything but an unconditional set. */
@@ -2811,6 +2834,7 @@ check_cond_move_block (basic_block bb,
rtx cond)
{
rtx_insn *insn;
+ rtx cc = cc_in_cond (cond);
/* We can only handle simple jumps at the end of the basic block.
It is almost impossible to update the CFG otherwise. */
@@ -2868,6 +2892,10 @@ check_cond_move_block (basic_block bb,
&& modified_between_p (src, insn, NEXT_INSN (BB_END (bb))))
return FALSE;
+ /* Skip it if the instruction to be moved might clobber CC. */
+ if (cc && set_of (cc, insn))
+ return FALSE;
+
vals->put (dest, src);
regs->safe_push (dest);
diff --git a/gcc/testsuite/gcc.dg/pr63917.c b/gcc/testsuite/gcc.dg/pr63917.c
new file mode 100644
index 0000000..422b15d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr63917.c
@@ -0,0 +1,45 @@
+/* { dg-options " -O3 " } */
+
+int d, i;
+
+struct S
+{
+ int f0;
+} *b, c, e, h, **g = &b;
+
+static struct S *f = &e;
+
+int
+fn1 (int p)
+{
+ int a = 0;
+ return a || p < 0 || p >= 2 || 1 >> p;
+}
+
+int
+main ()
+{
+ int k = 1, l, *m = &c.f0;
+
+ for (;;)
+ {
+ l = fn1 (i);
+ *m = k && i;
+ if (l)
+ {
+ int n[1] = {0};
+ }
+ break;
+ }
+
+ *g = &h;
+
+ if (d)
+ (*m)--;
+ d = (f != 0) | (i >= 0);
+
+ if (c.f0 != 0)
+ __builtin_abort ();
+
+ return 0;
+}
