Re: [PATCH] Don't optimize away non-pure/const calls during ccp (PR tree-optimization/51683)
On Wed, Dec 28, 2011 at 8:04 PM, Jakub Jelinek ja...@redhat.com wrote:
Hi!
For some calls (like memcpy and other builtins that are known to pass
through the first argument) we know the value of the lhs, but still
we shouldn't be replacing the call with just a mere assignment of that
known value to the LHS SSA_NAME, because the call has other side-effects.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux,
ok for trunk?
Ok.
Thanks,
Richard.
2011-12-28 Jakub Jelinek ja...@redhat.com
PR tree-optimization/51683
* tree-ssa-propagate.c (substitute_and_fold): Don't optimize away
calls with side-effects.
* tree-ssa-ccp.c (ccp_fold_stmt): Likewise.
* gcc.dg/pr51683.c: New test.
--- gcc/tree-ssa-propagate.c.jj 2011-11-11 20:54:59.0 +0100
+++ gcc/tree-ssa-propagate.c 2011-12-27 12:23:41.334187258 +0100
@@ -1056,6 +1056,12 @@ substitute_and_fold (ssa_prop_get_value_
}
else if (is_gimple_call (def_stmt))
{
+ int flags = gimple_call_flags (def_stmt);
+
+ /* Don't optimize away calls that have side-effects. */
+ if ((flags (ECF_CONST|ECF_PURE)) == 0
+ || (flags ECF_LOOPING_CONST_OR_PURE))
+ continue;
if (update_call_from_tree (gsi, val)
maybe_clean_or_replace_eh_stmt (def_stmt, gsi_stmt (gsi)))
gimple_purge_dead_eh_edges (gimple_bb (gsi_stmt (gsi)));
--- gcc/tree-ssa-ccp.c.jj 2011-12-19 09:21:07.0 +0100
+++ gcc/tree-ssa-ccp.c 2011-12-27 12:29:48.620880857 +0100
@@ -1878,6 +1878,7 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi
case GIMPLE_CALL:
{
tree lhs = gimple_call_lhs (stmt);
+ int flags = gimple_call_flags (stmt);
tree val;
tree argt;
bool changed = false;
@@ -1888,7 +1889,10 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi
type issues. */
if (lhs
TREE_CODE (lhs) == SSA_NAME
- (val = get_constant_value (lhs)))
+ (val = get_constant_value (lhs))
+ /* Don't optimize away calls that have side-effects. */
+ (flags (ECF_CONST|ECF_PURE)) != 0
+ (flags ECF_LOOPING_CONST_OR_PURE) == 0)
{
tree new_rhs = unshare_expr (val);
bool res;
--- gcc/testsuite/gcc.dg/pr51683.c.jj 2011-12-27 12:21:43.662925435 +0100
+++ gcc/testsuite/gcc.dg/pr51683.c 2011-12-27 12:21:23.0 +0100
@@ -0,0 +1,18 @@
+/* PR tree-optimization/51683 */
+/* { dg-do compile } */
+/* { dg-options -O2 -fdump-tree-optimized } */
+
+static inline void *
+bar (void *p, void *q, int r)
+{
+ return __builtin_memcpy (p, q, r);
+}
+
+void *
+foo (void *p)
+{
+ return bar ((void *) 0x12345000, p, 256);
+}
+
+/* { dg-final { scan-tree-dump memcpy optimized } } */
+/* { dg-final { cleanup-tree-dump optimized } } */
Jakub
[PATCH] Don't optimize away non-pure/const calls during ccp (PR tree-optimization/51683)
Hi!
For some calls (like memcpy and other builtins that are known to pass
through the first argument) we know the value of the lhs, but still
we shouldn't be replacing the call with just a mere assignment of that
known value to the LHS SSA_NAME, because the call has other side-effects.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux,
ok for trunk?
2011-12-28 Jakub Jelinek ja...@redhat.com
PR tree-optimization/51683
* tree-ssa-propagate.c (substitute_and_fold): Don't optimize away
calls with side-effects.
* tree-ssa-ccp.c (ccp_fold_stmt): Likewise.
* gcc.dg/pr51683.c: New test.
--- gcc/tree-ssa-propagate.c.jj 2011-11-11 20:54:59.0 +0100
+++ gcc/tree-ssa-propagate.c2011-12-27 12:23:41.334187258 +0100
@@ -1056,6 +1056,12 @@ substitute_and_fold (ssa_prop_get_value_
}
else if (is_gimple_call (def_stmt))
{
+ int flags = gimple_call_flags (def_stmt);
+
+ /* Don't optimize away calls that have side-effects. */
+ if ((flags (ECF_CONST|ECF_PURE)) == 0
+ || (flags ECF_LOOPING_CONST_OR_PURE))
+ continue;
if (update_call_from_tree (gsi, val)
maybe_clean_or_replace_eh_stmt (def_stmt, gsi_stmt (gsi)))
gimple_purge_dead_eh_edges (gimple_bb (gsi_stmt (gsi)));
--- gcc/tree-ssa-ccp.c.jj 2011-12-19 09:21:07.0 +0100
+++ gcc/tree-ssa-ccp.c 2011-12-27 12:29:48.620880857 +0100
@@ -1878,6 +1878,7 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi
case GIMPLE_CALL:
{
tree lhs = gimple_call_lhs (stmt);
+ int flags = gimple_call_flags (stmt);
tree val;
tree argt;
bool changed = false;
@@ -1888,7 +1889,10 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi
type issues. */
if (lhs
TREE_CODE (lhs) == SSA_NAME
-(val = get_constant_value (lhs)))
+(val = get_constant_value (lhs))
+ /* Don't optimize away calls that have side-effects. */
+(flags (ECF_CONST|ECF_PURE)) != 0
+(flags ECF_LOOPING_CONST_OR_PURE) == 0)
{
tree new_rhs = unshare_expr (val);
bool res;
--- gcc/testsuite/gcc.dg/pr51683.c.jj 2011-12-27 12:21:43.662925435 +0100
+++ gcc/testsuite/gcc.dg/pr51683.c 2011-12-27 12:21:23.0 +0100
@@ -0,0 +1,18 @@
+/* PR tree-optimization/51683 */
+/* { dg-do compile } */
+/* { dg-options -O2 -fdump-tree-optimized } */
+
+static inline void *
+bar (void *p, void *q, int r)
+{
+ return __builtin_memcpy (p, q, r);
+}
+
+void *
+foo (void *p)
+{
+ return bar ((void *) 0x12345000, p, 256);
+}
+
+/* { dg-final { scan-tree-dump memcpy optimized } } */
+/* { dg-final { cleanup-tree-dump optimized } } */
Jakub
Re: [PATCH] Don't optimize away non-pure/const calls during ccp (PR tree-optimization/51683)
- Original Message -
else if (is_gimple_call (def_stmt))
{
+ int flags = gimple_call_flags (def_stmt);
+
+ /* Don't optimize away calls that have side-effects. */
+ if ((flags (ECF_CONST|ECF_PURE)) == 0
+ || (flags ECF_LOOPING_CONST_OR_PURE))
This patch does this computation twice; grepping through the tree for ECF_CONST
suggests it's done quite a few more times. Could we get a predicate in
gimple.h to encapsulate this?
-Nathan
Re: [PATCH] Don't optimize away non-pure/const calls during ccp (PR tree-optimization/51683)
On Wed, Dec 28, 2011 at 11:53:41AM -0800, Nathan Froyd wrote:
- Original Message -
else if (is_gimple_call (def_stmt))
{
+ int flags = gimple_call_flags (def_stmt);
+
+ /* Don't optimize away calls that have side-effects. */
+ if ((flags (ECF_CONST|ECF_PURE)) == 0
+ || (flags ECF_LOOPING_CONST_OR_PURE))
This patch does this computation twice; grepping through the tree for
ECF_CONST suggests it's done quite a few more times. Could we get a
predicate in gimple.h to encapsulate this?
I think it would be an overkill to have a predicate for
nonlooping_const_or_pure_flags, we don't have predicates for similar
RTL or decl flags either.
We write:
/* We can delete dead const or pure calls as long as they do not
infinite loop. */
(RTL_CONST_OR_PURE_CALL_P (insn)
!RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)))
and not RTL_CONST_OR_PURE_NONLOOPING_CALL_P (insn) etc.
Jakub
