On Tue, 12 Jan 2021, Jakub Jelinek wrote:
> Hi!
>
> As the testcase shows, my latest changes caused ICE on that testcase.
> The problem is that arith_overflow_check_p now can change the use_stmt
> argument (has a reference), so that if it succeeds (returns non-zero),
> it points it to the GIMPLE_COND or EQ/NE or COND_EXPR assignment from the
> TRUNC_DIV_EXPR assignment.
> The problem was that it would change use_stmt also if it returned 0 in some
> cases, such as multiple imm uses of the division, and in one of the callers
> if arith_overflow_check_p returns 0 it looks at use_stmt again and performs
> other checks, which of course assumes that use_stmt is the one passed
> to arith_overflow_check_p and not e.g. NULL instead or some other unrelated
> stmt.
>
> The following patch fixes that by only changing use_stmt when we are about
> to return non-zero (for the MULT_EXPR case, which is the only one with the
> need to use different use_stmt).
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2021-01-12 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/98629
> * tree-ssa-math-opts.c (arith_overflow_check_p): Don't update use_stmt
> unless returning non-zero.
>
> * gcc.c-torture/compile/pr98629.c: New test.
>
> --- gcc/tree-ssa-math-opts.c.jj 2021-01-11 10:35:02.196501461 +0100
> +++ gcc/tree-ssa-math-opts.c 2021-01-11 23:56:24.154380944 +0100
> @@ -3667,6 +3667,7 @@ arith_overflow_check_p (gimple *stmt, gi
> tree rhs1 = gimple_assign_rhs1 (stmt);
> tree rhs2 = gimple_assign_rhs2 (stmt);
> tree multop = NULL_TREE, divlhs = NULL_TREE;
> + gimple *cur_use_stmt = use_stmt;
>
> if (code == MULT_EXPR)
> {
> @@ -3697,26 +3698,26 @@ arith_overflow_check_p (gimple *stmt, gi
> if (!divlhs)
> return 0;
> use_operand_p use;
> - if (!single_imm_use (divlhs, &use, &use_stmt))
> + if (!single_imm_use (divlhs, &use, &cur_use_stmt))
> return 0;
> }
> - if (gimple_code (use_stmt) == GIMPLE_COND)
> + if (gimple_code (cur_use_stmt) == GIMPLE_COND)
> {
> - ccode = gimple_cond_code (use_stmt);
> - crhs1 = gimple_cond_lhs (use_stmt);
> - crhs2 = gimple_cond_rhs (use_stmt);
> + ccode = gimple_cond_code (cur_use_stmt);
> + crhs1 = gimple_cond_lhs (cur_use_stmt);
> + crhs2 = gimple_cond_rhs (cur_use_stmt);
> }
> - else if (is_gimple_assign (use_stmt))
> + else if (is_gimple_assign (cur_use_stmt))
> {
> - if (gimple_assign_rhs_class (use_stmt) == GIMPLE_BINARY_RHS)
> + if (gimple_assign_rhs_class (cur_use_stmt) == GIMPLE_BINARY_RHS)
> {
> - ccode = gimple_assign_rhs_code (use_stmt);
> - crhs1 = gimple_assign_rhs1 (use_stmt);
> - crhs2 = gimple_assign_rhs2 (use_stmt);
> + ccode = gimple_assign_rhs_code (cur_use_stmt);
> + crhs1 = gimple_assign_rhs1 (cur_use_stmt);
> + crhs2 = gimple_assign_rhs2 (cur_use_stmt);
> }
> - else if (gimple_assign_rhs_code (use_stmt) == COND_EXPR)
> + else if (gimple_assign_rhs_code (cur_use_stmt) == COND_EXPR)
> {
> - tree cond = gimple_assign_rhs1 (use_stmt);
> + tree cond = gimple_assign_rhs1 (cur_use_stmt);
> if (COMPARISON_CLASS_P (cond))
> {
> ccode = TREE_CODE (cond);
> @@ -3792,11 +3793,17 @@ arith_overflow_check_p (gimple *stmt, gi
> {
> if ((crhs1 == divlhs && arith_cast_equal_p (crhs2, multop))
> || (crhs2 == divlhs && arith_cast_equal_p (crhs1, multop)))
> - return ccode == NE_EXPR ? 1 : -1;
> + {
> + use_stmt = cur_use_stmt;
> + return ccode == NE_EXPR ? 1 : -1;
> + }
> }
> else if ((crhs1 == divlhs && operand_equal_p (crhs2, multop, 0))
> || (crhs2 == divlhs && crhs1 == multop))
> - return ccode == NE_EXPR ? 1 : -1;
> + {
> + use_stmt = cur_use_stmt;
> + return ccode == NE_EXPR ? 1 : -1;
> + }
> }
> break;
> default:
> --- gcc/testsuite/gcc.c-torture/compile/pr98629.c.jj 2021-01-12
> 00:00:21.132949613 +0100
> +++ gcc/testsuite/gcc.c-torture/compile/pr98629.c 2021-01-11
> 23:59:58.178206894 +0100
> @@ -0,0 +1,11 @@
> +/* PR tree-optimization/98629 */
> +
> +unsigned int a;
> +int b, c;
> +
> +void
> +foo (void)
> +{
> + unsigned int *e = &a;
> + (a /= a |= b) - (0 <= (*e += *e)) * (c *= *e);
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
