rtlanal: Fix set_noop_p for volatile loads or stores [PR114768]
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Commit Message
Hi!
On the following testcase, combine propagates the mem/v load into mem store
with the same address and then removes it, because noop_move_p says it is a
no-op move. If it was the other way around, i.e. mem/v store and mem load,
or both would be mem/v, it would be kept.
The problem is that rtx_equal_p never checks any kind of flags on the rtxes
(and I think it would be quite dangerous to change it at this point), and
set_noop_p checks side_effects_p on just one of the operands, not both.
In the MEM <- MEM set, it only checks it on the destination, in
store to ZERO_EXTRACT only checks it on the source.
The following patch adds the missing side_effects_p checks.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2024-04-19 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/114768
* rtlanal.cc (set_noop_p): Don't return true for MEM <- MEM
sets if src has side-effects or for stores into ZERO_EXTRACT
if ZERO_EXTRACT operand has side-effects.
* gcc.dg/pr114768.c: New test.
Jakub
Comments
On Fri, 19 Apr 2024, Jakub Jelinek wrote:
> Hi!
>
> On the following testcase, combine propagates the mem/v load into mem store
> with the same address and then removes it, because noop_move_p says it is a
> no-op move. If it was the other way around, i.e. mem/v store and mem load,
> or both would be mem/v, it would be kept.
> The problem is that rtx_equal_p never checks any kind of flags on the rtxes
> (and I think it would be quite dangerous to change it at this point), and
> set_noop_p checks side_effects_p on just one of the operands, not both.
> In the MEM <- MEM set, it only checks it on the destination, in
> store to ZERO_EXTRACT only checks it on the source.
>
> The following patch adds the missing side_effects_p checks.
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2024-04-19 Jakub Jelinek <jakub@redhat.com>
>
> PR rtl-optimization/114768
> * rtlanal.cc (set_noop_p): Don't return true for MEM <- MEM
> sets if src has side-effects or for stores into ZERO_EXTRACT
> if ZERO_EXTRACT operand has side-effects.
>
> * gcc.dg/pr114768.c: New test.
>
> --- gcc/rtlanal.cc.jj 2024-02-24 12:45:28.674249100 +0100
> +++ gcc/rtlanal.cc 2024-04-18 15:09:55.199499083 +0200
> @@ -1637,12 +1637,15 @@ set_noop_p (const_rtx set)
> return true;
>
> if (MEM_P (dst) && MEM_P (src))
> - return rtx_equal_p (dst, src) && !side_effects_p (dst);
> + return (rtx_equal_p (dst, src)
> + && !side_effects_p (dst)
> + && !side_effects_p (src));
>
> if (GET_CODE (dst) == ZERO_EXTRACT)
> - return rtx_equal_p (XEXP (dst, 0), src)
> - && !BITS_BIG_ENDIAN && XEXP (dst, 2) == const0_rtx
> - && !side_effects_p (src);
> + return (rtx_equal_p (XEXP (dst, 0), src)
> + && !BITS_BIG_ENDIAN && XEXP (dst, 2) == const0_rtx
> + && !side_effects_p (src)
> + && !side_effects_p (XEXP (dst, 0)));
>
> if (GET_CODE (dst) == STRICT_LOW_PART)
> dst = XEXP (dst, 0);
> --- gcc/testsuite/gcc.dg/pr114768.c.jj 2024-04-18 15:37:49.139433678 +0200
> +++ gcc/testsuite/gcc.dg/pr114768.c 2024-04-18 15:43:30.389730365 +0200
> @@ -0,0 +1,10 @@
> +/* PR rtl-optimization/114768 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-rtl-final" } */
> +/* { dg-final { scan-rtl-dump "\\\(mem/v:" "final" { target { ! { nvptx*-*-* } } } } } */
> +
> +void
> +foo (int *p)
> +{
> + *p = *(volatile int *) p;
> +}
>
> Jakub
>
>
Hi Jakub!
On 2024-04-19T08:24:03+0200, Jakub Jelinek <jakub@redhat.com> wrote:
> --- gcc/testsuite/gcc.dg/pr114768.c.jj 2024-04-18 15:37:49.139433678 +0200
> +++ gcc/testsuite/gcc.dg/pr114768.c 2024-04-18 15:43:30.389730365 +0200
> @@ -0,0 +1,10 @@
> +/* PR rtl-optimization/114768 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-rtl-final" } */
> +/* { dg-final { scan-rtl-dump "\\\(mem/v:" "final" { target { ! { nvptx*-*-* } } } } } */
> +
> +void
> +foo (int *p)
> +{
> + *p = *(volatile int *) p;
> +}
Why exclude nvptx target here? As far as I can see, it does behave in
the exactly same way as expected; see 'diff' of before vs. after the
'gcc/rtlanal.cc' code changes:
PASS: gcc.dg/pr114768.c (test for excess errors)
[-FAIL:-]{+PASS:+} gcc.dg/pr114768.c scan-rtl-dump final "\\(mem/v:"
--- 0/pr114768.c.347r.final 2024-04-19 11:34:34.577037596 +0200
+++ ./pr114768.c.347r.final 2024-04-19 12:08:00.118312524 +0200
@@ -13,15 +13,27 @@
;; entry block defs 1 [%stack] 2 [%frame] 3 [%args]
;; exit block uses 1 [%stack] 2 [%frame]
;; regs ever live
-;; ref usage r1={1d,2u} r2={1d,2u} r3={1d,1u}
-;; total ref usage 8{3d,5u,0e} in 1{1 regular + 0 call} insns.
+;; ref usage r1={1d,3u} r2={1d,3u} r3={1d,2u} r22={1d,1u} r23={1d,2u}
+;; total ref usage 16{5d,11u,0e} in 4{4 regular + 0 call} insns.
(note 1 0 4 NOTE_INSN_DELETED)
(note 4 1 2 2 [bb 2] NOTE_INSN_BASIC_BLOCK)
-(note 2 4 3 2 NOTE_INSN_DELETED)
+(insn 2 4 3 2 (set (reg/v/f:DI 23 [ p ])
+ (unspec:DI [
+ (const_int 0 [0])
+ ] UNSPEC_ARG_REG)) "source-gcc/gcc/testsuite/gcc.dg/pr114768.c":8:1 14 {load_arg_regdi}
+ (nil))
(note 3 2 6 2 NOTE_INSN_FUNCTION_BEG)
-(note 6 3 10 2 NOTE_INSN_DELETED)
-(note 10 6 11 2 NOTE_INSN_EPILOGUE_BEG)
-(jump_insn 11 10 12 2 (return) "source-gcc/gcc/testsuite/gcc.dg/pr114768.c":10:1 289 {return}
+(insn 6 3 7 2 (set (reg:SI 22 [ _1 ])
+ (mem/v:SI (reg/v/f:DI 23 [ p ]) [1 MEM[(volatile int *)p_3(D)]+0 S4 A32])) "source-gcc/gcc/testsuite/gcc.dg/pr114768.c":9:8 6 {*movsi_insn}
+ (nil))
+(insn 7 6 10 2 (set (mem:SI (reg/v/f:DI 23 [ p ]) [1 *p_3(D)+0 S4 A32])
+ (reg:SI 22 [ _1 ])) "source-gcc/gcc/testsuite/gcc.dg/pr114768.c":9:6 6 {*movsi_insn}
+ (expr_list:REG_DEAD (reg/v/f:DI 23 [ p ])
+ (expr_list:REG_DEAD (reg:SI 22 [ _1 ])
+ (nil))))
+(note 10 7 13 2 NOTE_INSN_EPILOGUE_BEG)
+(note 13 10 11 3 [bb 3] NOTE_INSN_BASIC_BLOCK)
+(jump_insn 11 13 12 3 (return) "source-gcc/gcc/testsuite/gcc.dg/pr114768.c":10:1 289 {return}
(nil)
-> return)
(barrier 12 11 0)
--- 0/pr114768.s 2024-04-19 11:34:34.577037596 +0200
+++ ./pr114768.s 2024-04-19 12:08:00.118312524 +0200
@@ -13,5 +13,10 @@
{
.reg.u64 %ar0;
ld.param.u64 %ar0, [%in_ar0];
+ .reg.u32 %r22;
+ .reg.u64 %r23;
+ mov.u64 %r23, %ar0;
+ ld.u32 %r22, [%r23];
+ st.u32 [%r23], %r22;
ret;
}
Grüße
Thomas
On Fri, Apr 19, 2024 at 12:23:03PM +0200, Thomas Schwinge wrote:
> On 2024-04-19T08:24:03+0200, Jakub Jelinek <jakub@redhat.com> wrote:
> > --- gcc/testsuite/gcc.dg/pr114768.c.jj 2024-04-18 15:37:49.139433678 +0200
> > +++ gcc/testsuite/gcc.dg/pr114768.c 2024-04-18 15:43:30.389730365 +0200
> > @@ -0,0 +1,10 @@
> > +/* PR rtl-optimization/114768 */
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fdump-rtl-final" } */
> > +/* { dg-final { scan-rtl-dump "\\\(mem/v:" "final" { target { ! { nvptx*-*-* } } } } } */
> > +
> > +void
> > +foo (int *p)
> > +{
> > + *p = *(volatile int *) p;
> > +}
>
> Why exclude nvptx target here? As far as I can see, it does behave in
> the exactly same way as expected; see 'diff' of before vs. after the
> 'gcc/rtlanal.cc' code changes:
I wasn't sure if the non-RA targets (for which we don't have an effective
target) even have final dump.
If they do as you show, then guess the target guard can go.
Jakub
@@ -1637,12 +1637,15 @@ set_noop_p (const_rtx set)
return true;
if (MEM_P (dst) && MEM_P (src))
- return rtx_equal_p (dst, src) && !side_effects_p (dst);
+ return (rtx_equal_p (dst, src)
+ && !side_effects_p (dst)
+ && !side_effects_p (src));
if (GET_CODE (dst) == ZERO_EXTRACT)
- return rtx_equal_p (XEXP (dst, 0), src)
- && !BITS_BIG_ENDIAN && XEXP (dst, 2) == const0_rtx
- && !side_effects_p (src);
+ return (rtx_equal_p (XEXP (dst, 0), src)
+ && !BITS_BIG_ENDIAN && XEXP (dst, 2) == const0_rtx
+ && !side_effects_p (src)
+ && !side_effects_p (XEXP (dst, 0)));
if (GET_CODE (dst) == STRICT_LOW_PART)
dst = XEXP (dst, 0);
@@ -0,0 +1,10 @@
+/* PR rtl-optimization/114768 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-rtl-final" } */
+/* { dg-final { scan-rtl-dump "\\\(mem/v:" "final" { target { ! { nvptx*-*-* } } } } } */
+
+void
+foo (int *p)
+{
+ *p = *(volatile int *) p;
+}