On January 23, 2020 7:22:02 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>The following testcase is miscompiled, because the postreload pass
>changes:
>-(insn 14 13 23 2 (parallel [
>- (set (reg:DI 1 dx [94])
>- (plus:DI (reg:DI 1 dx [95])
>- (reg:DI 5 di [92])))
>- (clobber (reg:CC 17 flags))
>- ]) "pr93402.c":8:30 186 {*adddi_1}
>- (expr_list:REG_EQUAL (plus:DI (reg:DI 5 di [92])
>- (const_int 111111111111 [0x19debd01c7]))
>- (nil)))
>-(insn 23 14 25 2 (set (reg:SI 0 ax)
>+(insn 23 13 25 2 (set (reg:SI 0 ax)
> (const_int 0 [0])) "pr93402.c":10:1 67 {*movsi_internal}
> (nil))
> (insn 25 23 26 2 (use (reg:SI 0 ax)) "pr93402.c":10:1 -1
> (nil))
>-(insn 26 25 35 2 (use (reg:DI 1 dx)) "pr93402.c":10:1 -1
>+(insn 26 25 35 2 (use (plus:DI (reg:DI 1 dx [95])
>+ (reg:DI 5 di [92]))) "pr93402.c":10:1 -1
> (nil))
>A USE insn is not a normal insn and verify_changes called from
>apply_change_group is happy about any changes into it.
>The following patch avoids this optimization if we were to change
>the USE operand (this routine only changes a reg into (plus reg reg2)).
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and
>later for release branches?
Ok. Looks like the same thing Richard fixed for autoinc.
Richard.
>2020-01-23 Jakub Jelinek <ja...@redhat.com>
>
> PR rtl-optimization/93402
> * postreload.c (reload_combine_recognize_pattern): Don't try to adjust
> USE insns.
>
> * gcc.c-torture/execute/pr93402.c: New test.
>
>--- gcc/postreload.c.jj 2020-01-12 11:54:36.000000000 +0100
>+++ gcc/postreload.c 2020-01-23 17:23:25.359929516 +0100
>@@ -1078,6 +1078,10 @@ reload_combine_recognize_pattern (rtx_in
> struct reg_use *use = reg_state[regno].reg_use + i;
> if (GET_MODE (*use->usep) != mode)
> return false;
>+ /* Don't try to adjust (use (REGX)). */
>+ if (GET_CODE (PATTERN (use->insn)) == USE
>+ && &XEXP (PATTERN (use->insn), 0) == use->usep)
>+ return false;
> }
>
> /* Look for (set (REGX) (CONST_INT))
>--- gcc/testsuite/gcc.c-torture/execute/pr93402.c.jj 2020-01-23
>17:25:46.496803852 +0100
>+++ gcc/testsuite/gcc.c-torture/execute/pr93402.c 2020-01-23
>17:25:05.221425501 +0100
>@@ -0,0 +1,21 @@
>+/* PR rtl-optimization/93402 */
>+
>+struct S { unsigned int a; unsigned long long b; };
>+
>+__attribute__((noipa)) struct S
>+foo (unsigned long long x)
>+{
>+ struct S ret;
>+ ret.a = 0;
>+ ret.b = x * 11111111111ULL + 111111111111ULL;
>+ return ret;
>+}
>+
>+int
>+main ()
>+{
>+ struct S a = foo (1);
>+ if (a.a != 0 || a.b != 122222222222ULL)
>+ __builtin_abort ();
>+ return 0;
>+}
>
> Jakub
