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[PATCH] Maintain single-use chains in forwprop better
- From: Richard Guenther <rguenther at suse dot de>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 21 Jul 2011 13:30:12 +0200 (CEST)
- Subject: [PATCH] Maintain single-use chains in forwprop better
This is another place where we fail to properly keep single-use
chains by leaving around dead code. This confuses propagation
of comparisons which is restricted for non-single-uses.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2011-07-21 Richard Guenther <rguenther@suse.de>
* tree-ssa-forwprop.c (combine_conversions): Return whether
we have to run cfg-cleanup. Properly remove dead stmts.
(ssa_forward_propagate_and_combine): Adjust.
Index: gcc/tree-ssa-forwprop.c
===================================================================
--- gcc/tree-ssa-forwprop.c.orig 2011-07-21 12:12:36.000000000 +0200
+++ gcc/tree-ssa-forwprop.c 2011-07-21 12:05:13.000000000 +0200
@@ -2136,9 +2136,10 @@ out:
}
/* Combine two conversions in a row for the second conversion at *GSI.
- Returns true if there were any changes made. */
+ Returns 1 if there were any changes made, 2 if cfg-cleanup needs to
+ run. Else it returns 0. */
-static bool
+static int
combine_conversions (gimple_stmt_iterator *gsi)
{
gimple stmt = gsi_stmt (*gsi);
@@ -2155,15 +2156,15 @@ combine_conversions (gimple_stmt_iterato
if (useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (op0)))
{
gimple_assign_set_rhs_code (stmt, TREE_CODE (op0));
- return true;
+ return 1;
}
if (TREE_CODE (op0) != SSA_NAME)
- return false;
+ return 0;
def_stmt = SSA_NAME_DEF_STMT (op0);
if (!is_gimple_assign (def_stmt))
- return false;
+ return 0;
if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt)))
{
@@ -2202,7 +2203,7 @@ combine_conversions (gimple_stmt_iterato
gimple_assign_set_rhs1 (stmt, unshare_expr (defop0));
gimple_assign_set_rhs_code (stmt, TREE_CODE (defop0));
update_stmt (stmt);
- return true;
+ return remove_prop_source_from_use (op0) ? 2 : 1;
}
/* Likewise, if the intermediate and initial types are either both
@@ -2224,7 +2225,7 @@ combine_conversions (gimple_stmt_iterato
{
gimple_assign_set_rhs1 (stmt, defop0);
update_stmt (stmt);
- return true;
+ return remove_prop_source_from_use (op0) ? 2 : 1;
}
/* If we have a sign-extension of a zero-extended value, we can
@@ -2235,7 +2236,7 @@ combine_conversions (gimple_stmt_iterato
{
gimple_assign_set_rhs1 (stmt, defop0);
update_stmt (stmt);
- return true;
+ return remove_prop_source_from_use (op0) ? 2 : 1;
}
/* Two conversions in a row are not needed unless:
@@ -2264,7 +2265,7 @@ combine_conversions (gimple_stmt_iterato
{
gimple_assign_set_rhs1 (stmt, defop0);
update_stmt (stmt);
- return true;
+ return remove_prop_source_from_use (op0) ? 2 : 1;
}
/* A truncation to an unsigned type should be canonicalized as
@@ -2288,11 +2289,11 @@ combine_conversions (gimple_stmt_iterato
else
gimple_assign_set_rhs_from_tree (gsi, tem);
update_stmt (gsi_stmt (*gsi));
- return true;
+ return 1;
}
}
- return false;
+ return 0;
}
/* Main entry point for the forward propagation and statement combine
@@ -2454,7 +2455,12 @@ ssa_forward_propagate_and_combine (void)
else if (CONVERT_EXPR_CODE_P (code)
|| code == FLOAT_EXPR
|| code == FIX_TRUNC_EXPR)
- changed = combine_conversions (&gsi);
+ {
+ int did_something = combine_conversions (&gsi);
+ if (did_something == 2)
+ cfg_changed = true;
+ changed = did_something != 0;
+ }
break;
}