Eric Botcazou - [4.1] Fix PR rtl-optimization/30931 (original) (raw)

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• From: Eric Botcazou
• To: gcc-patches at gcc dot gnu dot org
• Date: Tue, 27 Feb 2007 21:24:55 +0100
• Subject: [4.1] Fix PR rtl-optimization/30931

It's again a regression from the 3.x series present on the 4.1 branch and due to the old loop optimizer, a variant of PR rtl-optimization/30787.

The GIV associated with the second p[i].first

for (i=0; i < 2; i++) while (p[i].first && p[i].done) p[i].first = 0;

is correctly detected as not "always executed", but it is nevertheless reduced because it is first combined with the "always executed" first p[i].first.

Fixed by disallowing combining for GIVs that are not "always executed".
Bootstrapped/regtested on x86_64-suse-linux and applied to 4.1 branch.

2007-02-27 Eric Botcazou ebotcazou@libertysurf.fr

    PR rtl-optimization/30931
    * loop.c (combine_givs_p): Return false if either GIV is not
always executed.

2007-02-27 Eric Botcazou ebotcazou@libertysurf.fr

    * gcc.c-torture/execute/20070227-1.c: New test.

-- Eric Botcazou

Index: loop.c

--- loop.c (revision 122251) +++ loop.c (working copy) @@ -8700,6 +8700,10 @@ combine_givs_p (struct induction *g1, st { rtx comb, ret;

• /* We cannot combine givs that are not always in sync. */
• if (!g1->always_executed || !g2->always_executed)
• return NULL_RTX;
• /* With the introduction of ext dependent givs, we must care for modes. G2 must not use a wider mode than G1. */ if (GET_MODE_SIZE (g1->mode) < GET_MODE_SIZE (g2->mode)) @@ -8708,6 +8712,7 @@ combine_givs_p (struct induction *g1, st ret = comb = express_from (g1, g2); if (comb == NULL_RTX) return NULL_RTX;
• if (g1->mode != g2->mode) ret = gen_lowpart (g2->mode, comb);

@@ -8718,9 +8723,7 @@ combine_givs_p (struct induction *g1, st combination to be the other way round. */ if (comb == g1->dest_reg && (g1->giv_type == DEST_REG || g2->giv_type == DEST_ADDR))

• {

•  return ret;

• }

• return ret;

/* If G2 can be expressed as a function of G1 and that function is valid as an address and no more expensive than using a register for G2,

/* PR rtl-optimization/30931 / / Testcase by Peter Bergner bergner@gcc.gnu.org */

struct s { int first; int done; };

void bug (struct s *p) { int i; for (i=0; i < 2; i++) { while (p[i].first && p[i].done) p[i].first = 0; } }

int main (void) { struct s array[2]; array[0].first = 1; array[0].done = 1; array[1].first = 0; array[1].done = 0;

bug (array);

return 0; }