[PATCH] tree-ssa-sink: Improve code sinking pass

[Ajit Agarwal <aagarwa1@linux.ibm.com>]

Hello Richard:

Currently, code sinking will sink code at the use points with loop having same
nesting depth. The following patch improves code sinking by placing the sunk
code in begining of the block after the labels.

For example :

void bar();
int j;
void foo(int a, int b, int c, int d, int e, int f)
{
  int l;
  l = a + b + c + d +e + f;
  if (a != 5)
    {
      bar();
      j = l;
    }
}

Code Sinking does the following:

void bar();
int j;
void foo(int a, int b, int c, int d, int e, int f)
{
  int l;

  if (a != 5)
    {
      l = a + b + c + d +e + f;
      bar();
      j = l;
    }
}

Bootstrapped regtested on powerpc64-linux-gnu.

Thanks & Regards

tree-ssa-sink: Improve code sinking pass

Currently, code sinking will sink code at the use points with loop having same
nesting depth. The following patch improves code sinking by placing the sunk
code in begining of the block after the labels.

2024-03-13  Ajit Kumar Agarwal  <aagarwa1@linux.ibm.com>

gcc/ChangeLog:

        PR tree-optimization/81953
        * tree-ssa-sink.cc (statement_sink_location):Sink statements at
	the begining of the basic block after labels.

gcc/testsuite/ChangeLog:

        PR tree-optimization/81953
        * gcc.dg/tree-ssa/ssa-sink-21.c: New test.
---
 gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c | 15 +++++++++++++++
 gcc/tree-ssa-sink.cc                        |  7 ++-----
 2 files changed, 17 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c
new file mode 100644
index 00000000000..d3b79ca5803
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-21.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-sink-stats" } */
+void bar();
+int j;
+void foo(int a, int b, int c, int d, int e, int f)
+{
+  int l;
+  l = a + b + c + d +e + f;
+  if (a != 5)
+    {
+      bar();
+      j = l;
+    }
+}
+/* { dg-final { scan-tree-dump {l_12\s+=\s+_4\s+\+\s+f_11\(D\);\n\s+bar\s+\(\)} sink1 } } */
diff --git a/gcc/tree-ssa-sink.cc b/gcc/tree-ssa-sink.cc
index 880d6f70a80..1ec5c048fe7 100644
--- a/gcc/tree-ssa-sink.cc
+++ b/gcc/tree-ssa-sink.cc
@@ -208,7 +208,6 @@ select_best_block (basic_block early_bb,
  	 loop nest.  */
       temp_bb = get_immediate_dominator (CDI_DOMINATORS, temp_bb);
     }
-
   /* Placing a statement before a setjmp-like function would be invalid
      (it cannot be reevaluated when execution follows an abnormal edge).
      If we selected a block with abnormal predecessors, just punt.  */
@@ -430,6 +429,7 @@ statement_sink_location (gimple *stmt, basic_block frombb,
 	    continue;
 	  break;
 	}
+
       use = USE_STMT (one_use);
 
       if (gimple_code (use) != GIMPLE_PHI)
@@ -439,10 +439,7 @@ statement_sink_location (gimple *stmt, basic_block frombb,
 	  if (sinkbb == frombb)
 	    return false;
 
-	  if (sinkbb == gimple_bb (use))
-	    *togsi = gsi_for_stmt (use);
-	  else
-	    *togsi = gsi_after_labels (sinkbb);
+	  *togsi = gsi_after_labels (sinkbb);
 
 	  return true;
 	}
-- 
2.39.3