mirror/gcc
2
0
Fork 0
mirror of git://gcc.gnu.org/git/gcc.git synced 2025-04-13 22:11:47 +08:00
Code Issues Packages Projects Releases Wiki Activity

widening_mul: Fix a > ~b to .ADD_OVERFLOW optimization [PR98256]

Browse Source 
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.

2020-12-13  Jakub Jelinek  <jakub@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.
This commit is contained in:
Jakub Jelinek 2020-12-13 19:25:33 +01:00
parent 3cc4e183f1
commit 49ec63666e
2 changed files with 25 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
gcc/testsuite/gcc.c-torture/compile/pr98256.c Normal file
View File

@ -0,0 +1,9 @@
/* PR tree-optimization/98256 */
unsigned a, b;
int
foo (void)
{
return !!(~a / b);
}

22
gcc/tree-ssa-math-opts.c
View File

@ -3598,6 +3598,7 @@ match_uaddsub_overflow (gimple_stmt_iterator *gsi, gimple *stmt,
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_iterator *gsi, gimple *stmt,
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_iterator *gsi, gimple *stmt,
}
}
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_iterator *gsi, gimple *stmt,
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_iterator *gsi, gimple *stmt,
}
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 (basic_block bb)
break;
case BIT_NOT_EXPR:
match_uaddsub_overflow (&gsi, stmt, code);
if (match_uaddsub_overflow (&gsi, stmt, code))
continue;
break;
case TRUNC_MOD_EXPR: