tree-ssa-math-opts: Fix up uaddc/usubc pattern matching [PR110271]
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Commit Message
Hi!
The following testcase ICEs, because I misremembered what the return value
from match_arith_overflow is. It isn't true if __builtin_*_overflow was
matched, but it is true only in the BIT_NOT_EXPR case if stmt was removed.
So, if match_arith_overflow matches something, gsi_stmt (gsi) will not
be stmt and match_uaddc_usubc will be confused and can ICE.
The following patch fixes it by checking if gsi_stmt (gsi) == stmt,
in that case we know it is still a PLUS_EXPR/MINUS_EXPR and we can try to
pattern match it further as UADDC/USUBC.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2023-06-16 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/110271
* tree-ssa-math-opts.cc (math_opts_dom_walker::after_dom_children)
<case PLUS_EXPR>: Ignore return value from match_arith_overflow,
instead call match_uaddc_usubc only if gsi_stmt (gsi) is still stmt.
* gcc.c-torture/compile/pr110271.c: New test.
Jakub
Comments
> Am 16.06.2023 um 16:23 schrieb Jakub Jelinek <jakub@redhat.com>:
>
> Hi!
>
> The following testcase ICEs, because I misremembered what the return value
> from match_arith_overflow is. It isn't true if __builtin_*_overflow was
> matched, but it is true only in the BIT_NOT_EXPR case if stmt was removed.
>
> So, if match_arith_overflow matches something, gsi_stmt (gsi) will not
> be stmt and match_uaddc_usubc will be confused and can ICE.
>
> The following patch fixes it by checking if gsi_stmt (gsi) == stmt,
> in that case we know it is still a PLUS_EXPR/MINUS_EXPR and we can try to
> pattern match it further as UADDC/USUBC.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok
Richard
> 2023-06-16 Jakub Jelinek <jakub@redhat.com>
>
> PR tree-optimization/110271
> * tree-ssa-math-opts.cc (math_opts_dom_walker::after_dom_children)
> <case PLUS_EXPR>: Ignore return value from match_arith_overflow,
> instead call match_uaddc_usubc only if gsi_stmt (gsi) is still stmt.
>
> * gcc.c-torture/compile/pr110271.c: New test.
>
> --- gcc/tree-ssa-math-opts.cc.jj 2023-06-15 09:12:28.777829348 +0200
> +++ gcc/tree-ssa-math-opts.cc 2023-06-16 10:44:31.231798664 +0200
> @@ -5558,9 +5558,12 @@ math_opts_dom_walker::after_dom_children
>
> case PLUS_EXPR:
> case MINUS_EXPR:
> - if (!convert_plusminus_to_widen (&gsi, stmt, code)
> - && !match_arith_overflow (&gsi, stmt, code, m_cfg_changed_p))
> - match_uaddc_usubc (&gsi, stmt, code);
> + if (!convert_plusminus_to_widen (&gsi, stmt, code))
> + {
> + match_arith_overflow (&gsi, stmt, code, m_cfg_changed_p);
> + if (gsi_stmt (gsi) == stmt)
> + match_uaddc_usubc (&gsi, stmt, code);
> + }
> break;
>
> case BIT_NOT_EXPR:
> --- gcc/testsuite/gcc.c-torture/compile/pr110271.c.jj 2023-06-16 10:57:32.757621687 +0200
> +++ gcc/testsuite/gcc.c-torture/compile/pr110271.c 2023-06-16 10:57:15.298871335 +0200
> @@ -0,0 +1,24 @@
> +/* PR tree-optimization/110271 */
> +
> +unsigned a, b, c, d, e;
> +
> +void
> +foo (unsigned *x, int y, unsigned int *z)
> +{
> + for (int i = 0; i < y; i++)
> + {
> + b += d;
> + a += b < d;
> + a += c = (__PTRDIFF_TYPE__) x > 3;
> + d = z[1] + (a < c);
> + a += e;
> + d += a < e;
> + }
> +}
> +
> +void
> +bar (unsigned int *z)
> +{
> + unsigned *x = x;
> + foo (x, 9, z);
> +}
>
> Jakub
>
@@ -5558,9 +5558,12 @@ math_opts_dom_walker::after_dom_children
case PLUS_EXPR:
case MINUS_EXPR:
- if (!convert_plusminus_to_widen (&gsi, stmt, code)
- && !match_arith_overflow (&gsi, stmt, code, m_cfg_changed_p))
- match_uaddc_usubc (&gsi, stmt, code);
+ if (!convert_plusminus_to_widen (&gsi, stmt, code))
+ {
+ match_arith_overflow (&gsi, stmt, code, m_cfg_changed_p);
+ if (gsi_stmt (gsi) == stmt)
+ match_uaddc_usubc (&gsi, stmt, code);
+ }
break;
case BIT_NOT_EXPR:
@@ -0,0 +1,24 @@
+/* PR tree-optimization/110271 */
+
+unsigned a, b, c, d, e;
+
+void
+foo (unsigned *x, int y, unsigned int *z)
+{
+ for (int i = 0; i < y; i++)
+ {
+ b += d;
+ a += b < d;
+ a += c = (__PTRDIFF_TYPE__) x > 3;
+ d = z[1] + (a < c);
+ a += e;
+ d += a < e;
+ }
+}
+
+void
+bar (unsigned int *z)
+{
+ unsigned *x = x;
+ foo (x, 9, z);
+}