| Message ID | 20130208002702.GL4385@tucnak.redhat.com |
|---|---|
| State | New |
| Headers | show |
From: Jakub Jelinek <jakub@redhat.com> Date: Fri, 8 Feb 2013 01:27:02 +0100 > +void > +fn (void) > +{ > + if (b) > + { > + int *p, *q; > + char g; > + > + if (f++) > + for (;; e++); > + lbl: > + for (b = 0; b < 2; b++) > + t /= d + 1 ? : i || a < c < (d = f) ? : 1 | (j = 2); > + > + *p = g >= *q ^ c != a ^ *p; I know this is "just a testcase" but it looks like both 'p' and 'q' can be uninitialized at this point.
On Thu, Feb 07, 2013 at 09:01:15PM -0500, David Miller wrote: > From: Jakub Jelinek <jakub@redhat.com> > Date: Fri, 8 Feb 2013 01:27:02 +0100 > > > +void > > +fn (void) > > +{ > > + if (b) > > + { > > + int *p, *q; > > + char g; > > + > > + if (f++) > > + for (;; e++); > > + lbl: > > + for (b = 0; b < 2; b++) > > + t /= d + 1 ? : i || a < c < (d = f) ? : 1 | (j = 2); > > + > > + *p = g >= *q ^ c != a ^ *p; > > I know this is "just a testcase" but it looks like both 'p' and 'q' > can be uninitialized at this point. Yeah, that is why it is just an dg-do assemble testcase, not dg-do run. The uninitialized vars are necessary to reproduce the problem, at least I haven't managed to adjust the testcase to reproduce without those. Jakub
On 13-02-07 7:27 PM, Jakub Jelinek wrote: > Hi! > > As the following testcase shows, get_reload_reg could sometimes return > a reused reg in a wrong mode. If curr_insn_input_reloads[i].input > and original have VOIDmode, they could compare equal (same integer > constant), yet mode might be different from > GET_MODE (curr_insn_input_reloads[i].reg). > If we need a wider reg than we already have, we can't reuse it easily, > but if we need a narrower one, we can just use a subreg of the wider one. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? > > 2013-02-07 Jakub Jelinek <jakub@redhat.com> > > PR rtl-optimization/56195 > * lra-constraints.c (get_reload_reg): Don't reuse regs > if they have smaller mode than requested, if they have > wider mode than requested, try to return a SUBREG. > > * gcc.dg/torture/pr56195.c: New test. > Sure, Jakub. Thanks.
--- gcc/lra-constraints.c.jj 2013-02-07 18:34:39.000000000 +0100 +++ gcc/lra-constraints.c 2013-02-07 20:58:25.558920536 +0100 @@ -421,8 +421,20 @@ get_reload_reg (enum op_type type, enum if (rtx_equal_p (curr_insn_input_reloads[i].input, original) && in_class_p (curr_insn_input_reloads[i].reg, rclass, &new_class)) { - *result_reg = curr_insn_input_reloads[i].reg; - regno = REGNO (*result_reg); + rtx reg = curr_insn_input_reloads[i].reg; + regno = REGNO (reg); + /* If input is equal to original and both are VOIDmode, + GET_MODE (reg) might be still different from mode. + Ensure we don't return *result_reg with wrong mode. */ + if (GET_MODE (reg) != mode) + { + if (GET_MODE_SIZE (GET_MODE (reg)) < GET_MODE_SIZE (mode)) + continue; + reg = lowpart_subreg (mode, reg, GET_MODE (reg)); + if (reg == NULL_RTX || GET_CODE (reg) != SUBREG) + continue; + } + *result_reg = reg; if (lra_dump_file != NULL) { fprintf (lra_dump_file, " Reuse r%d for reload ", regno); --- gcc/testsuite/gcc.dg/torture/pr56195.c.jj 2013-02-07 21:08:34.244334032 +0100 +++ gcc/testsuite/gcc.dg/torture/pr56195.c 2013-02-07 21:08:18.000000000 +0100 @@ -0,0 +1,31 @@ +/* PR rtl-optimization/56195 */ +/* { dg-do assemble } */ + +int i, a, t, b, c, d, e, f, j, *h; + +void +fn (void) +{ + if (b) + { + int *p, *q; + char g; + + if (f++) + for (;; e++); + lbl: + for (b = 0; b < 2; b++) + t /= d + 1 ? : i || a < c < (d = f) ? : 1 | (j = 2); + + *p = g >= *q ^ c != a ^ *p; + + if (!e) + { + q = p; + goto lbl; + } + } + + if (h++) + goto lbl; +}