simplify-rtx.c (simplify_binary_operation_1): Detect the identity.

2012-10-01  Marc Glisse  <marc.glisse@inria.fr>

gcc/
	* simplify-rtx.c (simplify_binary_operation_1) <VEC_SELECT>:
	Detect the identity.
	<VEC_CONCAT>: Handle VEC_SELECTs from the same vector.

gcc/testsuite/
	* gcc.target/i386/vect-rebuild.c: New testcase.

From-SVN: r191909

gcc/ChangeLog

+2012-10-01  Marc Glisse  <marc.glisse@inria.fr>
+
+	* simplify-rtx.c (simplify_binary_operation_1) <VEC_SELECT>:
+	Detect the identity.
+	<VEC_CONCAT>: Handle VEC_SELECTs from the same vector.
+
 2012-10-01  Oleg Endo  <olegendo@gcc.gnu.org>
 
 	PR target/50457

gcc/simplify-rtx.c

@@ -3246,6 +3246,23 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
 	      return gen_rtx_CONST_VECTOR (mode, v);
 	    }
 
+	  /* Recognize the identity.  */
+	  if (GET_MODE (trueop0) == mode)
+	    {
+	      bool maybe_ident = true;
+	      for (int i = 0; i < XVECLEN (trueop1, 0); i++)
+		{
+		  rtx j = XVECEXP (trueop1, 0, i);
+		  if (!CONST_INT_P (j) || INTVAL (j) != i)
+		    {
+		      maybe_ident = false;
+		      break;
+		    }
+		}
+	      if (maybe_ident)
+		return trueop0;
+	    }
+
 	  /* If we build {a,b} then permute it, build the result directly.  */
 	  if (XVECLEN (trueop1, 0) == 2
 	      && CONST_INT_P (XVECEXP (trueop1, 0, 0))
@@ -3371,6 +3388,24 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
 
 	    return gen_rtx_CONST_VECTOR (mode, v);
 	  }
+
+	/* Try to merge VEC_SELECTs from the same vector into a single one.  */
+	if (GET_CODE (trueop0) == VEC_SELECT
+	    && GET_CODE (trueop1) == VEC_SELECT
+	    && rtx_equal_p (XEXP (trueop0, 0), XEXP (trueop1, 0)))
+	  {
+	    rtx par0 = XEXP (trueop0, 1);
+	    rtx par1 = XEXP (trueop1, 1);
+	    int len0 = XVECLEN (par0, 0);
+	    int len1 = XVECLEN (par1, 0);
+	    rtvec vec = rtvec_alloc (len0 + len1);
+	    for (int i = 0; i < len0; i++)
+	      RTVEC_ELT (vec, i) = XVECEXP (par0, 0, i);
+	    for (int i = 0; i < len1; i++)
+	      RTVEC_ELT (vec, len0 + i) = XVECEXP (par1, 0, i);
+	    return simplify_gen_binary (VEC_SELECT, mode, XEXP (trueop0, 0),
+					gen_rtx_PARALLEL (VOIDmode, vec));
+	  }
       }
       return 0;
 

gcc/testsuite/ChangeLog

+2012-10-01  Marc Glisse  <marc.glisse@inria.fr>
+
+	* gcc.target/i386/vect-rebuild.c: New testcase.
+
 2012-09-30  Uros Bizjak  <ubizjak@gmail.com>
 
 	* gcc.target/i386/pad-10.c (foo2): Return x - z.

gcc/testsuite/gcc.target/i386/vect-rebuild.c

+/* { dg-do compile } */
+/* { dg-options "-O -mavx -fno-tree-forwprop" } */
+
+typedef double v2df __attribute__ ((__vector_size__ (16)));
+typedef double v4df __attribute__ ((__vector_size__ (32)));
+
+v2df f1 (v2df x)
+{
+  v2df xx = { x[0], x[1] };
+  return xx;
+}
+
+v4df f2 (v4df x)
+{
+  v4df xx = { x[0], x[1], x[2], x[3] };
+  return xx;
+}
+
+v2df g (v2df x)
+{
+  v2df xx = { x[1], x[0] };
+  return xx;
+}
+
+v2df h (v4df x)
+{
+  v2df xx = { x[2], x[3] };
+  return xx;
+}
+
+/* { dg-final { scan-assembler-not "unpck" } } */
+/* { dg-final { scan-assembler-times "\tv?permilpd\[ \t\]" 1 } } */
+/* { dg-final { scan-assembler-times "\tv?extractf128\[ \t\]" 1 } } */