re PR tree-optimization/88828 (Inefficient update of the first element of vector registers)

2019-05-14  Richard Biener  <rguenther@suse.de>
	H.J. Lu  <hongjiu.lu@intel.com>

	PR tree-optimization/88828
	* tree-ssa-forwprop.c (simplify_vector_constructor): Handle
	permuting in a single non-constant element not extracted
	from a vector.

	* gcc.target/i386/pr88828-1.c: New test.
	* gcc.target/i386/pr88828-1a.c: Likewise.
	* gcc.target/i386/pr88828-1b.c: Likewise.
	* gcc.target/i386/pr88828-1c.c: Likewise.
	* gcc.target/i386/pr88828-4a.c: Likewise.
	* gcc.target/i386/pr88828-4b.c: Likewise.
	* gcc.target/i386/pr88828-5a.c: Likewise.
	* gcc.target/i386/pr88828-5b.c: Likewise.
	* gcc.target/i386/pr88828-7.c: Likewise.
	* gcc.target/i386/pr88828-7a.c: Likewise.
	* gcc.target/i386/pr88828-7b.c: Likewise.
	* gcc.target/i386/pr88828-8.c: Likewise.
	* gcc.target/i386/pr88828-8a.c: Likewise.
	* gcc.target/i386/pr88828-8b.c: Likewise.
	* gcc.target/i386/pr88828-9.c: Likewise.
	* gcc.target/i386/pr88828-9a.c: Likewise.
	* gcc.target/i386/pr88828-9b.c: Likewise.

Co-Authored-By: H.J. Lu <hongjiu.lu@intel.com>

From-SVN: r271153

gcc/ChangeLog

@@ -1,3 +1,11 @@
+2019-05-14  Richard Biener  <rguenther@suse.de>
+	H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR tree-optimization/88828
+	* tree-ssa-forwprop.c (simplify_vector_constructor): Handle
+	permuting in a single non-constant element not extracted
+	from a vector.
+
 2019-05-14  Przemyslaw Wirkus  <przemyslaw.wirkus@arm.com\>
 
 	* internal-fn.def (SIGNBIT): New.

gcc/testsuite/ChangeLog

@@ -1,3 +1,25 @@
+2019-05-14  Richard Biener  <rguenther@suse.de>
+	H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR tree-optimization/88828
+	* gcc.target/i386/pr88828-1.c: New test.
+	* gcc.target/i386/pr88828-1a.c: Likewise.
+	* gcc.target/i386/pr88828-1b.c: Likewise.
+	* gcc.target/i386/pr88828-1c.c: Likewise.
+	* gcc.target/i386/pr88828-4a.c: Likewise.
+	* gcc.target/i386/pr88828-4b.c: Likewise.
+	* gcc.target/i386/pr88828-5a.c: Likewise.
+	* gcc.target/i386/pr88828-5b.c: Likewise.
+	* gcc.target/i386/pr88828-7.c: Likewise.
+	* gcc.target/i386/pr88828-7a.c: Likewise.
+	* gcc.target/i386/pr88828-7b.c: Likewise.
+	* gcc.target/i386/pr88828-8.c: Likewise.
+	* gcc.target/i386/pr88828-8a.c: Likewise.
+	* gcc.target/i386/pr88828-8b.c: Likewise.
+	* gcc.target/i386/pr88828-9.c: Likewise.
+	* gcc.target/i386/pr88828-9a.c: Likewise.
+	* gcc.target/i386/pr88828-9b.c: Likewise.
+
 2019-05-14  Przemyslaw Wirkus  <przemyslaw.wirkus@arm.com\>
 
 	* gcc.target/aarch64/signbitv4sf.c: New test.

gcc/testsuite/gcc.target/i386/pr88828-1.c

@@ -0,0 +1,49 @@
+/* { dg-do run { target sse2_runtime } } */
+/* { dg-options "-O2 -msse2" } */
+
+#include "pr88828-1a.c"
+#include "pr88828-1b.c"
+#include "pr88828-1c.c"
+
+extern void abort ();
+
+void
+do_check (__v4sf y, float f[4], float z)
+{
+  int i;
+
+  for (i = 0; i < 4; i++)
+    if (i == 0)
+      {
+	if (y[i] != z)
+	  abort ();
+      }
+    else
+      {
+	if (y[i] != f[i])
+	  abort ();
+      }
+}
+
+int
+main (void)
+{
+  float f[4] = { -11, 2, 55553, -4 };
+  float z = 134567;
+  __v4sf x = { f[0], f[1], f[2], f[3] };
+  __v4sf y;
+  int i;
+
+  for (i = 0; i < 4; i++)
+    if (x[i] != f[i])
+      abort ();
+
+  y = foo1 (x, z);
+  do_check (y, f, z);
+  y = foo2 (x, z);
+  do_check (y, f, z);
+  y = foo3 (x, z);
+  do_check (y, f, z);
+
+  return 0;
+}

gcc/testsuite/gcc.target/i386/pr88828-1a.c

@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler "movss" } } */
+/* { dg-final { scan-assembler-not "movaps" } } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+__attribute__((noinline, noclone))
+__v4sf
+foo1 (__v4sf x, float f)
+{
+  __v4sf y = { f, x[1], x[2], x[3] };
+  return y;
+}

gcc/testsuite/gcc.target/i386/pr88828-1b.c

@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler "movss" } } */
+/* { dg-final { scan-assembler-not "movaps" } } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+static __v4sf
+vector_init (float f0,float f1, float f2,float f3)
+{
+  __v4sf y = { f0, f1, f2, f3 };
+   return y;
+}
+
+__attribute__((noinline, noclone))
+__v4sf
+foo2 (__v4sf x, float f)
+{
+  return vector_init (f, x[1], x[2], x[3]) ;
+}

gcc/testsuite/gcc.target/i386/pr88828-1c.c

@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler "movss" } } */
+/* { dg-final { scan-assembler-not "movaps" } } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+__attribute__((noinline, noclone))
+__v4sf
+foo3 (__v4sf x, float f)
+{
+  __v4sf y = x;
+  y[0] = f;
+  return y;
+}

gcc/testsuite/gcc.target/i386/pr88828-4a.c

@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler "movss" } } */
+/* { dg-final { scan-assembler-times "shufps" 1 } } */
+/* { dg-final { scan-assembler-not "movaps" } } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+__attribute__((noinline, noclone))
+__v4sf
+foo (__v4sf x, float f)
+{
+  __v4sf y = { x[0], x[2], x[3], x[1] };
+  y[0] = f;
+  return y;
+}

gcc/testsuite/gcc.target/i386/pr88828-4b.c

@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mavx" } */
+/* { dg-final { scan-assembler-times "vpermilps" 1 } } */
+/* { dg-final { scan-assembler-times "vmovss" 1 { target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-times "vpinsrd" 1 { target ia32 } } } */
+/* { dg-final { scan-assembler-not "vmovss" { target ia32 } } } */
+/* { dg-final { scan-assembler-not "vshufps" } } */
+/* { dg-final { scan-assembler-not "vmovaps" } } */
+/* { dg-final { scan-assembler-not "vmovlhps" } } */
+/* { dg-final { scan-assembler-not "vunpcklps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+__attribute__((noinline, noclone))
+__v4sf
+foo (__v4sf x, float f)
+{
+  __v4sf y = { x[0], x[2], x[3], x[1] };
+  y[0] = f;
+  return y;
+}

gcc/testsuite/gcc.target/i386/pr88828-5a.c

@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler "movss" } } */
+/* { dg-final { scan-assembler-times "shufps" 2 } } */
+/* { dg-final { scan-assembler-times "movaps" 1 } } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+__attribute__((noinline, noclone))
+__v4sf
+foo (__v4sf x, float f)
+{
+  __v4sf y = { x[0], x[2], x[3], x[0] };
+  y[3] = f;
+  return y;
+}

gcc/testsuite/gcc.target/i386/pr88828-5b.c

@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mavx" } */
+/* { dg-final { scan-assembler-times "vpermilps" 1 } } */
+/* { dg-final { scan-assembler-times "vinsertps" 1 } } */
+/* { dg-final { scan-assembler-not "vshufps" } } */
+/* { dg-final { scan-assembler-not "vmovss" } } */
+/* { dg-final { scan-assembler-not "vmovaps" } } */
+/* { dg-final { scan-assembler-not "vmovlhps" } } */
+/* { dg-final { scan-assembler-not "vunpcklps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+__attribute__((noinline, noclone))
+__v4sf
+foo (__v4sf x, float f)
+{
+  __v4sf y = { x[0], x[2], x[3], x[0] };
+  y[3] = f;
+  return y;
+}

gcc/testsuite/gcc.target/i386/pr88828-7.c

@@ -0,0 +1,53 @@
+/* { dg-do run { target sse2_runtime } } */
+/* { dg-options "-O2 -msse2 -fexcess-precision=standard" } */
+
+#include "pr88828-7a.c"
+#include "pr88828-7b.c"
+
+extern void abort ();
+
+float
+bar (float x, float y)
+{
+  return x / y - y * x;
+}
+
+void
+do_check (__v4sf x, float f1[4], float f2[4])
+{
+  int i;
+
+  for (i = 0; i < 4; i++)
+    if (i == 0)
+      {
+	if (x[i] != bar (f1[i], f2[i]))
+	  abort ();
+      }
+    else
+      {
+	if (x[i] != f1[i])
+	  abort ();
+      }
+}
+
+int
+main (void)
+{
+  float f1[4] = { -11, 2, 55553, -4 };
+  float f2[4] = { 111, 3.3, -55.553, 4.8 };
+  __v4sf x = { f1[0], f1[1], f1[2], f1[3] };
+  __v4sf y = { f2[0], f2[1], f2[2], f2[3] };
+  __v4sf z;
+  int i;
+
+  for (i = 0; i < 4; i++)
+    if (x[i] != f1[i] || y[i] != f2[i] )
+      abort ();
+
+  z = foo1 (x, y);
+  do_check (z, f1, f2);
+  x = foo2 (x, y);
+  do_check (z, f1, f2);
+
+  return 0;
+}

gcc/testsuite/gcc.target/i386/pr88828-7a.c

@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpckhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+extern float bar (float, float);
+
+__v4sf
+foo1 (__v4sf x, __v4sf y)
+{
+  __v4sf z = { bar (x[0], y[0]), x[1], x[2], x[3] };
+  return z;
+}

gcc/testsuite/gcc.target/i386/pr88828-7b.c

@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpckhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+extern float bar (float, float);
+
+static __v4sf
+vector_init (float f0,float f1, float f2,float f3)
+{
+  __v4sf y = { f0, f1, f2, f3 };
+   return y;
+}
+
+__v4sf
+foo2 (__v4sf x, __v4sf y)
+{
+  return vector_init (bar (x[0], y[0]), x[1], x[2], x[3]) ;
+}

gcc/testsuite/gcc.target/i386/pr88828-8.c

@@ -0,0 +1,46 @@
+/* { dg-do run { target sse2_runtime } } */
+/* { dg-options "-O2 -msse2" } */
+
+#include "pr88828-8a.c"
+#include "pr88828-8b.c"
+
+extern void abort ();
+
+void
+do_check (__v4sf y, float f[4], float z)
+{
+  int i;
+
+  for (i = 0; i < 4; i++)
+    if (i == 0)
+      {
+	if (y[i] != z)
+	  abort ();
+      }
+    else
+      {
+	if (y[i] != f[i])
+	  abort ();
+      }
+}
+
+int
+main (void)
+{
+  float f[4] = { -11, 2, 55553, -4 };
+  float z = 11.4;
+  __v4sf x = { f[0], f[1], f[2], f[3] };
+  __v4sf y;
+  int i;
+
+  for (i = 0; i < 4; i++)
+    if (x[i] != f[i])
+      abort ();
+
+  y = foo1 (x);
+  do_check (y, f, z);
+  y = foo2 (x);
+  do_check (y, f, z);
+
+  return 0;
+}

gcc/testsuite/gcc.target/i386/pr88828-8a.c

@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpckhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+__v4sf
+foo1 (__v4sf x)
+{
+  __v4sf z = { 11.4, x[1], x[2], x[3] };
+  return z;
+}

gcc/testsuite/gcc.target/i386/pr88828-8b.c

@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpckhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+
+static __v4sf
+vector_init (float f0,float f1, float f2,float f3)
+{
+  __v4sf y = { f0, f1, f2, f3 };
+   return y;
+}
+
+__v4sf
+foo2 (__v4sf x)
+{
+  return vector_init (11.4, x[1], x[2], x[3]) ;
+}

gcc/testsuite/gcc.target/i386/pr88828-9.c

@@ -0,0 +1,46 @@
+/* { dg-do run { target sse2_runtime } } */
+/* { dg-options "-O2 -msse2" } */
+
+#include "pr88828-9a.c"
+#include "pr88828-9b.c"
+
+extern void abort ();
+
+void
+do_check (__v4sf y, float f[4], float z)
+{
+  int i;
+
+  for (i = 0; i < 4; i++)
+    if (i == 0)
+      {
+	if (y[i] != z)
+	  abort ();
+      }
+    else
+      {
+	if (y[i] != f[i])
+	  abort ();
+      }
+}
+
+int
+main (void)
+{
+  float f[4] = { -11, 2, 55553, -4 };
+  float z = 11.4;
+  __m128 x = (__m128) (__v4sf) { f[0], f[1], f[2], f[3] };
+  __m128 y;
+  int i;
+
+  for (i = 0; i < 4; i++)
+    if (x[i] != f[i])
+      abort ();
+
+  y = foo1 (x);
+  do_check (y, f, z);
+  y = foo2 (x);
+  do_check (y, f, z);
+
+  return 0;
+}

gcc/testsuite/gcc.target/i386/pr88828-9a.c

@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpckhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+typedef float __m128 __attribute__ ((__vector_size__ (16), __may_alias__));
+
+__m128
+foo1 (__m128 x)
+{
+  __v4sf z = { 11.4, ((__v4sf) x)[1], ((__v4sf) x)[2], ((__v4sf) x) [3] };
+  return (__m128) z;
+}

gcc/testsuite/gcc.target/i386/pr88828-9b.c

@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse -mno-sse4" } */
+/* { dg-final { scan-assembler-not "movlhps" } } */
+/* { dg-final { scan-assembler-not "unpckhps" } } */
+/* { dg-final { scan-assembler-not "unpcklps" } } */
+/* { dg-final { scan-assembler-not "shufps" } } */
+
+typedef float __v4sf __attribute__ ((__vector_size__ (16)));
+typedef float __m128 __attribute__ ((__vector_size__ (16), __may_alias__));
+
+static __m128
+vector_init (float f0,float f1, float f2,float f3)
+{
+  __v4sf y = { f0, f1, f2, f3 };
+   return (__m128) y;
+}
+
+__m128
+foo2 (__m128 x)
+{
+  return vector_init (11.4, ((__v4sf) x)[1], ((__v4sf) x)[2],
+		      ((__v4sf) x) [3]);
+}

gcc/tree-ssa-forwprop.c

@@ -2065,71 +2065,87 @@ simplify_vector_constructor (gimple_stmt_iterator *gsi)
   conv_code = ERROR_MARK;
   maybe_ident = true;
   tree one_constant = NULL_TREE;
+  tree one_nonconstant = NULL_TREE;
   auto_vec<tree> constants;
   constants.safe_grow_cleared (nelts);
   FOR_EACH_VEC_SAFE_ELT (CONSTRUCTOR_ELTS (op), i, elt)
     {
       tree ref, op1;
+      unsigned int elem;
 
       if (i >= nelts)
 	return false;
 
+      /* Look for elements extracted and possibly converted from
+         another vector.  */
       op1 = get_bit_field_ref_def (elt->value, conv_code);
-      if (op1)
+      if (op1
+	  && TREE_CODE ((ref = TREE_OPERAND (op1, 0))) == SSA_NAME
+	  && VECTOR_TYPE_P (TREE_TYPE (ref))
+	  && useless_type_conversion_p (TREE_TYPE (op1),
+					TREE_TYPE (TREE_TYPE (ref)))
+	  && known_eq (bit_field_size (op1), elem_size)
+	  && constant_multiple_p (bit_field_offset (op1),
+				  elem_size, &elem))
 	{
-	  ref = TREE_OPERAND (op1, 0);
 	  unsigned int j;
 	  for (j = 0; j < 2; ++j)
 	    {
 	      if (!orig[j])
 		{
-		  if (TREE_CODE (ref) != SSA_NAME)
-		    return false;
-		  if (! VECTOR_TYPE_P (TREE_TYPE (ref))
-		      || ! useless_type_conversion_p (TREE_TYPE (op1),
-						      TREE_TYPE (TREE_TYPE (ref))))
-		    return false;
-		  if (j && !useless_type_conversion_p (TREE_TYPE (orig[0]),
-						       TREE_TYPE (ref)))
-		    return false;
-		  orig[j] = ref;
-		  break;
+		  if (j == 0
+		      || useless_type_conversion_p (TREE_TYPE (orig[0]),
+						    TREE_TYPE (ref)))
+		    break;
 		}
 	      else if (ref == orig[j])
 		break;
 	    }
-	  if (j == 2)
-	    return false;
-
-	  unsigned int elt;
-	  if (maybe_ne (bit_field_size (op1), elem_size)
-	      || !constant_multiple_p (bit_field_offset (op1), elem_size, &elt))
-	    return false;
-	  if (j)
-	    elt += nelts;
-	  if (elt != i)
-	    maybe_ident = false;
-	  sel.quick_push (elt);
+	  /* Found a suitable vector element.  */
+	  if (j <= 2)
+	    {
+	      orig[j] = ref;
+	      if (j)
+		elem += nelts;
+	      if (elem != i)
+		maybe_ident = false;
+	      sel.quick_push (elem);
+	      continue;
+	    }
+	  /* Else fallthru.  */
 	}
-      else if (CONSTANT_CLASS_P (elt->value))
+      /* Handle elements not extracted from a vector.
+          1. constants by permuting with constant vector
+	  2. a unique non-constant element by permuting with a splat vector  */
+      if (orig[1]
+	  && orig[1] != error_mark_node)
+	return false;
+      orig[1] = error_mark_node;
+      if (CONSTANT_CLASS_P (elt->value))
 	{
-	  if (orig[1]
-	      && orig[1] != error_mark_node)
+	  if (one_nonconstant)
 	    return false;
-	  orig[1] = error_mark_node;
 	  if (!one_constant)
 	    one_constant = elt->value;
 	  constants[i] = elt->value;
-	  sel.quick_push (i + nelts);
-	  maybe_ident = false;
 	}
       else
-	return false;
+	{
+	  if (one_constant)
+	    return false;
+	  if (!one_nonconstant)
+	    one_nonconstant = elt->value;
+	  else if (!operand_equal_p (one_nonconstant, elt->value, 0))
+	    return false;
+	}
+      sel.quick_push (i + nelts);
+      maybe_ident = false;
     }
   if (i < nelts)
     return false;
 
-  if (! VECTOR_TYPE_P (TREE_TYPE (orig[0]))
+  if (! orig[0]
+      || ! VECTOR_TYPE_P (TREE_TYPE (orig[0]))
       || maybe_ne (TYPE_VECTOR_SUBPARTS (type),
 		   TYPE_VECTOR_SUBPARTS (TREE_TYPE (orig[0]))))
     return false;
@@ -2165,9 +2181,19 @@ simplify_vector_constructor (gimple_stmt_iterator *gsi)
 		       GET_MODE_SIZE (TYPE_MODE (type))))
 	return false;
       op2 = vec_perm_indices_to_tree (mask_type, indices);
+      bool convert_orig0 = false;
       if (!orig[1])
 	orig[1] = orig[0];
-      if (orig[1] == error_mark_node)
+      else if (orig[1] == error_mark_node
+	       && one_nonconstant)
+	{
+	  gimple_seq seq = NULL;
+	  orig[1] = gimple_build_vector_from_val (&seq, UNKNOWN_LOCATION,
+						  type, one_nonconstant);
+	  gsi_insert_seq_before (gsi, seq, GSI_SAME_STMT);
+	  convert_orig0 = true;
+	}
+      else if (orig[1] == error_mark_node)
 	{
 	  tree_vector_builder vec (type, nelts, 1);
 	  for (unsigned i = 0; i < nelts; ++i)
@@ -2177,11 +2203,12 @@ simplify_vector_constructor (gimple_stmt_iterator *gsi)
 	      /* ??? Push a don't-care value.  */
 	      vec.quick_push (one_constant);
 	  orig[1] = vec.build ();
+	  convert_orig0 = true;
 	}
       if (conv_code == ERROR_MARK)
 	gimple_assign_set_rhs_with_ops (gsi, VEC_PERM_EXPR, orig[0],
 					orig[1], op2);
-      else if (TREE_CODE (orig[1]) == VECTOR_CST)
+      else if (convert_orig0)
 	{
 	  gimple *conv
 	    = gimple_build_assign (make_ssa_name (type), conv_code, orig[0]);