Hi!
Unfortunately, my latest tree-ssa-math-opts.c patch broke the following
testcase. The problem is that the code is adding .ADD_OVERFLOW or
.SUB_OVERFLOW before or after the stmt on which the function has been
called, which is normally a addition or subtraction that has all the
operands.
But in the a > ~b optimization that stmt is the ~b stmt and the other
comparison operand might be defined only after that ~b stmt, so we can't
insert the .ADD_OVERFLOW next to ~b that we want to delete, but need to
insert it before the a > temp comparison that uses it; and in that case
when removing the BIT_NOT_EXPR stmt we need to ensure the caller doesn't do
gsi_next because gsi_remove already points the iterator to the next stmt.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2020-12-13 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/98256
* tree-ssa-math-opts.c (match_uaddsub_overflow): For BIT_NOT_EXPR,
only handle a single use, and insert .ADD_OVERFLOW before the
comparison rather than after the BIT_NOT_EXPR. Return true iff
it is BIT_NOT_EXPR and it has been removed.
(math_opts_dom_walker::after_dom_children) <case BIT_NOT_EXPR>:
If match_uaddsub_overflow returned true, continue instead of break.
* gcc.c-torture/compile/pr98256.c: New test.
--- gcc/tree-ssa-math-opts.c.jj 2020-12-12 14:48:40.195306781 +0100
+++ gcc/tree-ssa-math-opts.c 2020-12-12 22:42:24.474396562 +0100
@@ -3598,6 +3598,7 @@ match_uaddsub_overflow (gimple_stmt_iter
gimple *use_stmt;
gimple *add_stmt = NULL;
bool add_first = false;
+ gimple *cond_stmt = NULL;
gcc_checking_assert (code == PLUS_EXPR
|| code == MINUS_EXPR
@@ -3628,8 +3629,9 @@ match_uaddsub_overflow (gimple_stmt_iter
return false;
if (rhs2 == NULL)
rhs2 = other;
- else if (rhs2 != other)
+ else
return false;
+ cond_stmt = use_stmt;
}
ovf_use_seen = true;
}
@@ -3818,6 +3820,9 @@ match_uaddsub_overflow (gimple_stmt_iter
}
}
+ if (code == BIT_NOT_EXPR)
+ *gsi = gsi_for_stmt (cond_stmt);
+
tree ctype = build_complex_type (type);
gcall *g = gimple_build_call_internal (code != MINUS_EXPR
? IFN_ADD_OVERFLOW : IFN_SUB_OVERFLOW,
@@ -3843,7 +3848,10 @@ match_uaddsub_overflow (gimple_stmt_iter
tree ovf = make_ssa_name (type);
g2 = gimple_build_assign (ovf, IMAGPART_EXPR,
build1 (IMAGPART_EXPR, type, ctmp));
- gsi_insert_after (gsi, g2, GSI_NEW_STMT);
+ if (code != BIT_NOT_EXPR)
+ gsi_insert_after (gsi, g2, GSI_NEW_STMT);
+ else
+ gsi_insert_before (gsi, g2, GSI_SAME_STMT);
FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs)
{
@@ -3908,11 +3916,12 @@ match_uaddsub_overflow (gimple_stmt_iter
}
else if (code == BIT_NOT_EXPR)
{
- gimple_stmt_iterator gsi2 = gsi_for_stmt (stmt);
- gsi_remove (&gsi2, true);
+ *gsi = gsi_for_stmt (stmt);
+ gsi_remove (gsi, true);
release_ssa_name (lhs);
+ return true;
}
- return true;
+ return false;
}
/* Return true if target has support for divmod. */
@@ -4238,7 +4247,8 @@ math_opts_dom_walker::after_dom_children
break;
case BIT_NOT_EXPR:
- match_uaddsub_overflow (&gsi, stmt, code);
+ if (match_uaddsub_overflow (&gsi, stmt, code))
+ continue;
break;
case TRUNC_MOD_EXPR:
--- gcc/testsuite/gcc.c-torture/compile/pr98256.c.jj 2020-12-12
22:44:34.037940761 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr98256.c 2020-12-12
22:35:54.452778912 +0100
@@ -0,0 +1,9 @@
+/* PR tree-optimization/98256 */
+
+unsigned a, b;
+
+int
+foo (void)
+{
+ return !!(~a / b);
+}
Jakub
