combine vec_perm_expr with constructor

[Marc Glisse <marc dot glisse at inria dot fr>]

Hello,

this patch (bootstrapped and regtested on x86_64) deals with the same 
issue as the one at:

http://gcc.gnu.org/ml/gcc-patches/2012-08/msg00205.html

that is combining a shuffle of a constructor into a constructor, but at 
the tree-ssa level. An advantage is that it works with any size of vectors 
(the RTL patch only handles size 2 IIRC). A drawback is that it only 
applies to __builtin_shuffle, not the builtins that the x86 front-end 
uses.

Note that fold already knew this optimization (my thanks to whoever wrote 
it, it helped a lot), it just never got a chance to apply it.

In the call to fold_ternary, I am not sure if TREE_TYPE(op0) is the right 
argument, I could also use the type of the lhs, I don't know if that would 
make any difference.


While I am here, I would like to write a patch that converts w={v[1],v[0]} 
to a builtin_shuffle (under the same conditions where a builtin_shuffle is 
not lowered to a constructor of elements, obviously). Is forwprop still 
the right pass to add it, or is there another more relevant one?


2012-08-22  Marc Glisse  <marc.glisse@inria.fr>

gcc/
	* tree-ssa-forwprop.c (simplify_permutation): Handle CONSTRUCTOR.

gcc/testsuite/
 	* gcc.dg/tree-ssa/forwprop-20.c: New testcase.

--
Marc Glisse

Index: testsuite/gcc.dg/tree-ssa/forwprop-20.c
===================================================================
--- testsuite/gcc.dg/tree-ssa/forwprop-20.c	(revision 0)
+++ testsuite/gcc.dg/tree-ssa/forwprop-20.c	(revision 0)
@@ -0,0 +1,70 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target double64 } */
+/* { dg-options "-O2 -fdump-tree-optimized" }  */
+
+#include <stdint.h>
+
+/* All of these optimizations happen for unsupported vector modes as a
+   consequence of the lowering pass. We need to test with a vector mode
+   that is supported by default on at least some architectures, or make
+   the test target specific so we can pass a flag like -mavx.  */
+
+typedef double vecf __attribute__ ((vector_size (2 * sizeof (double))));
+typedef int64_t veci __attribute__ ((vector_size (2 * sizeof (int64_t))));
+
+void f (double d, vecf* r)
+{
+  vecf x = { -d, 5 };
+  vecf y = {  1, 4 };
+  veci m = {  2, 0 };
+  *r = __builtin_shuffle (x, y, m); // { 1, -d }
+}
+
+void g (float d, vecf* r)
+{
+  vecf x = { d, 5 };
+  vecf y = { 1, 4 };
+  veci m = { 2, 1 };
+  *r = __builtin_shuffle (x, y, m); // { 1, 5 }
+}
+
+void h (double d, vecf* r)
+{
+  vecf x = { d + 1, 5 };
+  vecf y = {   1  , 4 };
+  veci m = {   2  , 0 };
+  *r = __builtin_shuffle (y, x, m); // { d + 1, 1 }
+}
+
+void i (float d, vecf* r)
+{
+  vecf x = { d, 5 };
+  veci m = { 1, 0 };
+  *r = __builtin_shuffle (x, m); // { 5, d }
+}
+
+void j (vecf* r)
+{
+  vecf y = {  1, 2 };
+  veci m = {  0, 0 };
+  *r = __builtin_shuffle (y, m); // { 1, 1 }
+}
+
+void k (vecf* r)
+{
+  vecf x = {  3, 4 };
+  vecf y = {  1, 2 };
+  veci m = {  3, 0 };
+  *r = __builtin_shuffle (x, y, m); // { 2, 3 }
+}
+
+void l (double d, vecf* r)
+{
+  vecf x = { -d, 5 };
+  vecf y = {  d, 4 };
+  veci m = {  2, 0 };
+  *r = __builtin_shuffle (x, y, m); // { d, -d }
+}
+
+/* { dg-final { scan-tree-dump-not "VEC_PERM_EXPR" "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */

Property changes on: testsuite/gcc.dg/tree-ssa/forwprop-20.c
___________________________________________________________________
Added: svn:keywords
   + Author Date Id Revision URL
Added: svn:eol-style
   + native

Index: tree-ssa-forwprop.c
===================================================================
--- tree-ssa-forwprop.c	(revision 190666)
+++ tree-ssa-forwprop.c	(working copy)
@@ -2602,75 +2602,130 @@ is_combined_permutation_identity (tree m
       if (j == i)
 	maybe_identity2 = false;
       else if (j == i + nelts)
 	maybe_identity1 = false;
       else
 	return 0;
     }
   return maybe_identity1 ? 1 : maybe_identity2 ? 2 : 0;
 }
 
-/* Combine two shuffles in a row.  Returns 1 if there were any changes
-   made, 2 if cfg-cleanup needs to run.  Else it returns 0.  */
+/* Combine a shuffle with its arguments.  Returns 1 if there were any
+   changes made, 2 if cfg-cleanup needs to run.  Else it returns 0.  */
  
 static int
 simplify_permutation (gimple_stmt_iterator *gsi)
 {
   gimple stmt = gsi_stmt (*gsi);
   gimple def_stmt;
-  tree op0, op1, op2, op3;
-  enum tree_code code = gimple_assign_rhs_code (stmt);
-  enum tree_code code2;
+  tree op0, op1, op2, op3, arg0, arg1;
+  enum tree_code code;
 
-  gcc_checking_assert (code == VEC_PERM_EXPR);
+  gcc_checking_assert (gimple_assign_rhs_code (stmt) == VEC_PERM_EXPR);
 
   op0 = gimple_assign_rhs1 (stmt);
   op1 = gimple_assign_rhs2 (stmt);
   op2 = gimple_assign_rhs3 (stmt);
 
-  if (TREE_CODE (op0) != SSA_NAME)
-    return 0;
-
   if (TREE_CODE (op2) != VECTOR_CST)
     return 0;
 
-  if (op0 != op1)
-    return 0;
+  if (TREE_CODE (op0) == VECTOR_CST)
+    {
+      code = VECTOR_CST;
+      arg0 = op0;
+    }
+  else if (TREE_CODE (op0) == SSA_NAME)
+    {
+      def_stmt = SSA_NAME_DEF_STMT (op0);
+      if (!def_stmt || !is_gimple_assign (def_stmt)
+	  || !can_propagate_from (def_stmt))
+	return 0;
 
-  def_stmt = SSA_NAME_DEF_STMT (op0);
-  if (!def_stmt || !is_gimple_assign (def_stmt)
-      || !can_propagate_from (def_stmt))
+      code = gimple_assign_rhs_code (def_stmt);
+      arg0 = gimple_assign_rhs1 (def_stmt);
+    }
+  else
     return 0;
 
-  code2 = gimple_assign_rhs_code (def_stmt);
-
   /* Two consecutive shuffles.  */
-  if (code2 == VEC_PERM_EXPR)
+  if (code == VEC_PERM_EXPR)
     {
       tree orig;
       int ident;
+
+      if (op0 != op1)
+	return 0;
       op3 = gimple_assign_rhs3 (def_stmt);
       if (TREE_CODE (op3) != VECTOR_CST)
 	return 0;
       ident = is_combined_permutation_identity (op3, op2);
       if (!ident)
 	return 0;
       orig = (ident == 1) ? gimple_assign_rhs1 (def_stmt)
 			  : gimple_assign_rhs2 (def_stmt);
       gimple_assign_set_rhs1 (stmt, unshare_expr (orig));
       gimple_assign_set_rhs_code (stmt, TREE_CODE (orig));
       gimple_set_num_ops (stmt, 2);
       update_stmt (stmt);
       return remove_prop_source_from_use (op0) ? 2 : 1;
     }
 
-  return false;
+  /* Shuffle of a constructor.  */
+  else if (code == CONSTRUCTOR || code == VECTOR_CST)
+    {
+      tree opt;
+      bool ret = false;
+      if (op0 != op1)
+	{
+	  if (TREE_CODE (op1) == VECTOR_CST)
+	    arg1 = op1;
+	  else if (TREE_CODE (op1) == SSA_NAME)
+	    {
+	      enum tree_code code2;
+	      gimple def_stmt2 = SSA_NAME_DEF_STMT (op1);
+	      if (!def_stmt2 || !is_gimple_assign (def_stmt2)
+		  || !can_propagate_from (def_stmt2))
+		return 0;
+
+	      code2 = gimple_assign_rhs_code (def_stmt2);
+	      if (code2 != CONSTRUCTOR && code2 != VECTOR_CST)
+		return 0;
+	      arg1 = gimple_assign_rhs1 (def_stmt2);
+	    }
+	  else
+	    return 0;
+
+	  if ((TREE_CODE (op0) == SSA_NAME && !has_single_use (op0))
+	      || (TREE_CODE (op1) == SSA_NAME && !has_single_use (op1)))
+	    return 0;
+	}
+      else
+	{
+	  /* Already used twice in this statement.  */
+	  if (TREE_CODE (op0) == SSA_NAME && num_imm_uses (op0) > 2)
+	    return 0;
+	  arg1 = arg0;
+	}
+      opt = fold_ternary (VEC_PERM_EXPR, TREE_TYPE(op0), arg0, arg1, op2);
+      if (!opt)
+	return 0;
+      gimple_assign_set_rhs_from_tree (gsi, opt);
+      update_stmt (gsi_stmt (*gsi));
+      if (TREE_CODE (op0) == SSA_NAME)
+	ret = remove_prop_source_from_use (op0);
+      if (op0 != op1 && TREE_CODE (op1) == SSA_NAME)
+	ret |= remove_prop_source_from_use (op1);
+      return ret ? 2 : 1;
+    }
+
+  return 0;
 }
 
 /* Main entry point for the forward propagation and statement combine
    optimizer.  */
 
 static unsigned int
 ssa_forward_propagate_and_combine (void)
 {
   basic_block bb;
   unsigned int todoflags = 0;