Re: [tree-optimization/61607] Look through SSA_NAME_VALUE chains

2014-07-17 Thread Jeff Law 

On 07/07/14 03:02, Richard Biener wrote:

On Mon, Jun 30, 2014 at 8:56 AM, Jeff Law l...@redhat.com wrote:


SSA_NAME_VALUE is, in effect, a chain of values.  ie, it's possible for
SSA_NAME_VALUE of any given SSA_NAME to refer to another SSA_NAME.


Hmm, but it shouldn't  as we walk in dominator order and should
always do set_ssa_name_value (name, ssa_name_value (value))
there shouldn't be any chains.
They're certainly there and always have been.  You can get chains in 
cases where we derive implicit sets, for example as well as due to loops 
in the CFG.





But maybe I'm missing sth about the lattice used by DOM here ...
(at least none of the callers in DOM care to valueize 'value' before
setting it as value for an SSA name).
It's not really a lattice in the way you'd see in VRP.  It's just an 
equality relationship with an unwinding stack to allow us to restore 
state from earlier points in the domwalk.




jeff

Re: [tree-optimization/61607] Look through SSA_NAME_VALUE chains

2014-07-07 Thread Richard Biener 
On Mon, Jun 30, 2014 at 8:56 AM, Jeff Law l...@redhat.com wrote:

 SSA_NAME_VALUE is, in effect, a chain of values.  ie, it's possible for
 SSA_NAME_VALUE of any given SSA_NAME to refer to another SSA_NAME.

Hmm, but it shouldn't  as we walk in dominator order and should
always do set_ssa_name_value (name, ssa_name_value (value))
there shouldn't be any chains.

But maybe I'm missing sth about the lattice used by DOM here ...
(at least none of the callers in DOM care to valueize 'value' before
setting it as value for an SSA name).

Richard.

  In many
 cases it is advantageous to look deeper into those chains, particularly when
 simplifying conditionals for jump threading.

 The problem with simply following the chains, is they can have loops. This
 can occur when we're threading across a loop backedge.

 I did some fairly simple experiments which showed that chains of 0, or 1
 element are by far the most common.  chains of 2 elements are rare, but do
 occur in practice (such as pr61607).  Chains of  2 elements consistently
 have loops.

 So this patch just looks up to two elements deep in the chain and avoids the
 complication of explicitly looking for loops.  This allows us to pick up the
 obvious equivalency in pr61607 and gets the jumps outside the loop fully
 threaded.

 Bootstrapped and regression tested on x86_64-unknown-linux-gnu. Installed on
 the trunk.






 commit 3e2754da946eb64d7a1d30548c9b6119cda3a014
 Author: Jeff Law l...@redhat.com
 Date:   Sun Jun 29 23:35:50 2014 -0600

 tree-optimization/61607
 * tree-ssa-threadedge.c (simplify_control_stmt_condition): Look
 deeper into the SSA_NAME_VALUE chain.

 tree-optimization/61607
 * gcc.dg/tree-ssa/pr61607.c: New test.

 diff --git a/gcc/ChangeLog b/gcc/ChangeLog
 index 4cc167a..6dfe1d3 100644
 --- a/gcc/ChangeLog
 +++ b/gcc/ChangeLog
 @@ -1,3 +1,9 @@
 +2014-06-30  Jeff Law  l...@redhat.com
 +
 +   tree-optimization/61607
 +   * tree-ssa-threadedge.c (simplify_control_stmt_condition): Look
 +   deeper into the SSA_NAME_VALUE chain.
 +
  2014-06-30  Zhenqiang Chen  zhenqiang.c...@linaro.org

 * loop-invariant.c (get_inv_cost): Handle register class.
 diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
 index 5a9d73a..1df9d4e 100644
 --- a/gcc/testsuite/ChangeLog
 +++ b/gcc/testsuite/ChangeLog
 @@ -1,3 +1,8 @@
 +2014-06-30  Jeff Law  l...@redhat.com
 +
 +   tree-optimization/61607
 +   * gcc.dg/tree-ssa/pr61607.c: New test.
 +
  2014-06-30  Zhenqiang Chen  zhenqiang.c...@linaro.org

 * ira-loop-pressure.c: New test.
 diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr61607.c
 b/gcc/testsuite/gcc.dg/tree-ssa/pr61607.c
 new file mode 100644
 index 000..ec00f51
 --- /dev/null
 +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr61607.c
 @@ -0,0 +1,29 @@
 +/* { dg-do compile } */
 +/* { dg-options -Os -fno-tree-fre -fdump-tree-dom1 } */
 +
 +void foo(int *);
 +void f2(int dst[3], int R)
 +{
 +  int i, inter[2];
 +  _Bool inter0p = 0;
 +  _Bool inter1p = 0;
 +  for (i = 1; i  R; i++)
 +{
 +  inter0p = 1;
 +  inter1p = 1;
 +}
 +  if (inter0p)
 +inter[0] = 1;
 +  if (inter1p)
 +inter[1] = 1;
 +  foo(inter);
 +}
 +
 +
 +/* There should be precisely two conditionals.  One for the loop condition
 +   and one for the test after the loop.  Previously we failed to eliminate
 +   the second conditional after the loop.  */
 +/* { dg-final { scan-tree-dump-times if 2 dom1} } */
 +
 +/* { dg-final { cleanup-tree-dump dom1 } } */
 +
 diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
 index a76a7ce..9807b42 100644
 --- a/gcc/tree-ssa-threadedge.c
 +++ b/gcc/tree-ssa-threadedge.c
 @@ -542,16 +542,26 @@ simplify_control_stmt_condition (edge e,
/* Get the current value of both operands.  */
if (TREE_CODE (op0) == SSA_NAME)
 {
 -  tree tmp = SSA_NAME_VALUE (op0);
 - if (tmp)
 -   op0 = tmp;
 + for (int i = 0; i  2; i++)
 +   {
 + if (TREE_CODE (op0) == SSA_NAME
 +  SSA_NAME_VALUE (op0))
 +   op0 = SSA_NAME_VALUE (op0);
 + else
 +   break;
 +   }
 }

if (TREE_CODE (op1) == SSA_NAME)
 {
 - tree tmp = SSA_NAME_VALUE (op1);
 - if (tmp)
 -   op1 = tmp;
 + for (int i = 0; i  2; i++)
 +   {
 + if (TREE_CODE (op1) == SSA_NAME
 +  SSA_NAME_VALUE (op1))
 +   op1 = SSA_NAME_VALUE (op1);
 + else
 +   break;
 +   }
 }

if (handle_dominating_asserts)
 @@ -625,10 +635,17 @@ simplify_control_stmt_condition (edge e,
  It is possible to get loops in the SSA_NAME_VALUE chains
  (consider threading the backedge of a loop where we have
  a loop invariant SSA_NAME used in the condition.  */
 -  if (cached_lhs
 -  TREE_CODE (cached_lhs) == SSA_NAME
 -

[tree-optimization/61607] Look through SSA_NAME_VALUE chains

2014-06-30 Thread Jeff Law 


SSA_NAME_VALUE is, in effect, a chain of values.  ie, it's possible for 
SSA_NAME_VALUE of any given SSA_NAME to refer to another SSA_NAME.  In 
many cases it is advantageous to look deeper into those chains, 
particularly when simplifying conditionals for jump threading.


The problem with simply following the chains, is they can have loops. 
This can occur when we're threading across a loop backedge.


I did some fairly simple experiments which showed that chains of 0, or 1 
element are by far the most common.  chains of 2 elements are rare, but 
do occur in practice (such as pr61607).  Chains of  2 elements 
consistently have loops.


So this patch just looks up to two elements deep in the chain and avoids 
the complication of explicitly looking for loops.  This allows us to 
pick up the obvious equivalency in pr61607 and gets the jumps outside 
the loop fully threaded.


Bootstrapped and regression tested on x86_64-unknown-linux-gnu. 
Installed on the trunk.






commit 3e2754da946eb64d7a1d30548c9b6119cda3a014
Author: Jeff Law l...@redhat.com
Date:   Sun Jun 29 23:35:50 2014 -0600

tree-optimization/61607
* tree-ssa-threadedge.c (simplify_control_stmt_condition): Look
deeper into the SSA_NAME_VALUE chain.

tree-optimization/61607
* gcc.dg/tree-ssa/pr61607.c: New test.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4cc167a..6dfe1d3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2014-06-30  Jeff Law  l...@redhat.com
+
+   tree-optimization/61607
+   * tree-ssa-threadedge.c (simplify_control_stmt_condition): Look
+   deeper into the SSA_NAME_VALUE chain.
+
 2014-06-30  Zhenqiang Chen  zhenqiang.c...@linaro.org
 
* loop-invariant.c (get_inv_cost): Handle register class.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5a9d73a..1df9d4e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2014-06-30  Jeff Law  l...@redhat.com
+
+   tree-optimization/61607
+   * gcc.dg/tree-ssa/pr61607.c: New test.
+
 2014-06-30  Zhenqiang Chen  zhenqiang.c...@linaro.org
 
* ira-loop-pressure.c: New test.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr61607.c 
b/gcc/testsuite/gcc.dg/tree-ssa/pr61607.c
new file mode 100644
index 000..ec00f51
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr61607.c
@@ -0,0 +1,29 @@
+/* { dg-do compile } */
+/* { dg-options -Os -fno-tree-fre -fdump-tree-dom1 } */
+
+void foo(int *);
+void f2(int dst[3], int R)
+{
+  int i, inter[2];
+  _Bool inter0p = 0;
+  _Bool inter1p = 0;
+  for (i = 1; i  R; i++)
+{
+  inter0p = 1;
+  inter1p = 1;
+}
+  if (inter0p)
+inter[0] = 1;
+  if (inter1p)
+inter[1] = 1;
+  foo(inter);
+}
+
+
+/* There should be precisely two conditionals.  One for the loop condition
+   and one for the test after the loop.  Previously we failed to eliminate
+   the second conditional after the loop.  */
+/* { dg-final { scan-tree-dump-times if 2 dom1} } */
+ 
+/* { dg-final { cleanup-tree-dump dom1 } } */
+
diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
index a76a7ce..9807b42 100644
--- a/gcc/tree-ssa-threadedge.c
+++ b/gcc/tree-ssa-threadedge.c
@@ -542,16 +542,26 @@ simplify_control_stmt_condition (edge e,
   /* Get the current value of both operands.  */
   if (TREE_CODE (op0) == SSA_NAME)
{
-  tree tmp = SSA_NAME_VALUE (op0);
- if (tmp)
-   op0 = tmp;
+ for (int i = 0; i  2; i++)
+   {
+ if (TREE_CODE (op0) == SSA_NAME
+  SSA_NAME_VALUE (op0))
+   op0 = SSA_NAME_VALUE (op0);
+ else
+   break;
+   }
}
 
   if (TREE_CODE (op1) == SSA_NAME)
{
- tree tmp = SSA_NAME_VALUE (op1);
- if (tmp)
-   op1 = tmp;
+ for (int i = 0; i  2; i++)
+   {
+ if (TREE_CODE (op1) == SSA_NAME
+  SSA_NAME_VALUE (op1))
+   op1 = SSA_NAME_VALUE (op1);
+ else
+   break;
+   }
}
 
   if (handle_dominating_asserts)
@@ -625,10 +635,17 @@ simplify_control_stmt_condition (edge e,
 It is possible to get loops in the SSA_NAME_VALUE chains
 (consider threading the backedge of a loop where we have
 a loop invariant SSA_NAME used in the condition.  */
-  if (cached_lhs
-  TREE_CODE (cached_lhs) == SSA_NAME
-  SSA_NAME_VALUE (cached_lhs))
-   cached_lhs = SSA_NAME_VALUE (cached_lhs);
+  if (cached_lhs)
+   {
+ for (int i = 0; i  2; i++)
+   {
+ if (TREE_CODE (cached_lhs) == SSA_NAME
+  SSA_NAME_VALUE (cached_lhs))
+   cached_lhs = SSA_NAME_VALUE (cached_lhs);
+ else
+   break;
+   }
+   }
 
   /* If we're dominated by a suitable ASSERT_EXPR, then
 update CACHED_LHS appropriately.  */