Hi,
this is an ICE building the gnattools on ARM, a regression present on the
mainline (and reproducible on x86/Linux by switching to SJLJ exceptions).
For the reduced testcase compiled at -O:
Unable to coalesce ssa_names 2 and 174 which are marked as MUST COALESCE.
comp_last_2(ab) and comp_last_174(ab)
+===========================GNAT BUG DETECTED==============================+
| 4.7.0 20110626 (experimental) [trunk revision 175408] (i586-suse-linux-gnu)
GCC error:|
| SSA corruption |
| Error detected around p.adb:3:4
The SSA names (or rather 2 related ones) have overlapping lifetimes. The
problem is created by forwprop1. Before:
<bb 23>:
# comp_last_1(ab) = PHI <comp_last_159(ab)(20), comp_last_2(ab)(22)>
[...]
comp_last_174(ab) = comp_last_1(ab) + 1;
D.2425_175 = args.P_BOUNDS;
D.2426_176 = D.2425_175->LB0;
if (D.2426_176 > comp_last_174(ab))
goto <bb 39>;
else
goto <bb 38>;
<bb 38>:
D.2425_177 = args.P_BOUNDS;
D.2427_178 = D.2425_177->UB0;
if (D.2427_178 < comp_last_174(ab))
goto <bb 39>;
else
goto <bb 40>;
[...]
comp_last_185(ab) = comp_last_174(ab) + 1;
D.2425_186 = args.P_BOUNDS;
D.2426_187 = D.2425_186->LB0;
if (D.2426_187 > comp_last_185(ab))
goto <bb 43>;
else
goto <bb 42>;
After:
comp_last_185(ab) = comp_last_1(ab) + 2;
D.2425_186 = args.P_BOUNDS;
D.2426_187 = D.2425_186->LB0;
if (D.2426_187 > comp_last_185(ab))
goto <bb 43>;
else
goto <bb 42>;
The pass already contains a check for this situation in can_propagate_from but
it isn't applied in this case.
Tested on x86_64-suse-linux, OK for the mainline?
2011-06-28 Eric Botcazou <ebotca...@adacore.com>
PR tree-optimization/49539
* tree-ssa-forwprop.c (can_propagate_from): Check for abnormal SSA
by means of stmt_references_abnormal_ssa_name.
(associate_plusminus): Call can_propagate_from before propagating
from definition statements.
(ssa_forward_propagate_and_combine): Remove superfluous newline.
--
Eric Botcazou
Index: tree-ssa-forwprop.c
===================================================================
--- tree-ssa-forwprop.c (revision 175408)
+++ tree-ssa-forwprop.c (working copy)
@@ -260,9 +260,6 @@ get_prop_source_stmt (tree name, bool si
static bool
can_propagate_from (gimple def_stmt)
{
- use_operand_p use_p;
- ssa_op_iter iter;
-
gcc_assert (is_gimple_assign (def_stmt));
/* If the rhs has side-effects we cannot propagate from it. */
@@ -280,9 +277,8 @@ can_propagate_from (gimple def_stmt)
return true;
/* We cannot propagate ssa names that occur in abnormal phi nodes. */
- FOR_EACH_SSA_USE_OPERAND (use_p, def_stmt, iter, SSA_OP_USE)
- if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (use_p)))
- return false;
+ if (stmt_references_abnormal_ssa_name (def_stmt))
+ return false;
/* If the definition is a conversion of a pointer to a function type,
then we can not apply optimizations as some targets require
@@ -1780,7 +1776,8 @@ associate_plusminus (gimple stmt)
{
gimple def_stmt = SSA_NAME_DEF_STMT (rhs2);
if (is_gimple_assign (def_stmt)
- && gimple_assign_rhs_code (def_stmt) == NEGATE_EXPR)
+ && gimple_assign_rhs_code (def_stmt) == NEGATE_EXPR
+ && can_propagate_from (def_stmt))
{
code = (code == MINUS_EXPR) ? PLUS_EXPR : MINUS_EXPR;
gimple_assign_set_rhs_code (stmt, code);
@@ -1797,7 +1794,8 @@ associate_plusminus (gimple stmt)
{
gimple def_stmt = SSA_NAME_DEF_STMT (rhs1);
if (is_gimple_assign (def_stmt)
- && gimple_assign_rhs_code (def_stmt) == NEGATE_EXPR)
+ && gimple_assign_rhs_code (def_stmt) == NEGATE_EXPR
+ && can_propagate_from (def_stmt))
{
code = MINUS_EXPR;
gimple_assign_set_rhs_code (stmt, code);
@@ -1840,7 +1838,7 @@ associate_plusminus (gimple stmt)
if (TREE_CODE (rhs1) == SSA_NAME)
{
gimple def_stmt = SSA_NAME_DEF_STMT (rhs1);
- if (is_gimple_assign (def_stmt))
+ if (is_gimple_assign (def_stmt) && can_propagate_from (def_stmt))
{
enum tree_code def_code = gimple_assign_rhs_code (def_stmt);
if (def_code == PLUS_EXPR
@@ -1940,7 +1938,7 @@ associate_plusminus (gimple stmt)
if (rhs2 && TREE_CODE (rhs2) == SSA_NAME)
{
gimple def_stmt = SSA_NAME_DEF_STMT (rhs2);
- if (is_gimple_assign (def_stmt))
+ if (is_gimple_assign (def_stmt) && can_propagate_from (def_stmt))
{
enum tree_code def_code = gimple_assign_rhs_code (def_stmt);
if (def_code == PLUS_EXPR
@@ -2262,8 +2260,7 @@ ssa_forward_propagate_and_combine (void)
else
gsi_next (&gsi);
}
- else if (code == POINTER_PLUS_EXPR
- && can_propagate_from (stmt))
+ else if (code == POINTER_PLUS_EXPR && can_propagate_from (stmt))
{
if (TREE_CODE (gimple_assign_rhs2 (stmt)) == INTEGER_CST
/* ??? Better adjust the interface to that function
