[PATCH] Fix *vec_duplicate_p (PR rtl-optimization/83682)

[Jakub Jelinek]

Hi!

All the vec_duplicate_p uses in simplify-rtx.c assume that it returns vector
element if it returns true, and while that is the case for CONST_VECTOR
which can't contain anything but scalars, VEC_DUPLICATE is documented:
"This operation converts a scalar into a vector or a small vector into a
larger one by duplicating the input values.  The output vector mode must have
the same submodes as the input vector mode or the scalar modes, and the
number of output parts must be an integer multiple of the number of input
parts." and e.g. on x86 that is heavily used in the backend.
So, simplify-rtx.c checks something and expects to be given a scalar
element, but it can return something different with a different (vector)
mode instead.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2018-01-05  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/83682
        * rtl.h (const_vec_duplicate_p): Only return true for VEC_DUPLICATE
        if it has non-VECTOR_MODE element mode.
        (vec_duplicate_p): Likewise.

        * gcc.target/i386/pr83682.c: New test.

--- gcc/rtl.h.jj        2018-01-04 00:43:14.704702340 +0100
+++ gcc/rtl.h   2018-01-05 16:03:52.420823342 +0100
@@ -2969,7 +2969,9 @@ const_vec_duplicate_p (T x, T *elt)
       *elt = CONST_VECTOR_ENCODED_ELT (x, 0);
       return true;
     }
-  if (GET_CODE (x) == CONST && GET_CODE (XEXP (x, 0)) == VEC_DUPLICATE)
+  if (GET_CODE (x) == CONST
+      && GET_CODE (XEXP (x, 0)) == VEC_DUPLICATE
+      && !VECTOR_MODE_P (GET_MODE (XEXP (XEXP (x, 0), 0))))
     {
       *elt = XEXP (XEXP (x, 0), 0);
       return true;
@@ -2984,7 +2986,8 @@ template <typename T>
 inline bool
 vec_duplicate_p (T x, T *elt)
 {
-  if (GET_CODE (x) == VEC_DUPLICATE)
+  if (GET_CODE (x) == VEC_DUPLICATE
+      && !VECTOR_MODE_P (GET_MODE (XEXP (x, 0))))
     {
       *elt = XEXP (x, 0);
       return true;
--- gcc/testsuite/gcc.target/i386/pr83682.c.jj  2018-01-05 16:06:57.299885887 
+0100
+++ gcc/testsuite/gcc.target/i386/pr83682.c     2018-01-05 16:06:26.630875486 
+0100
@@ -0,0 +1,17 @@
+/* PR rtl-optimization/83682 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -msse2" } */
+
+typedef float V __attribute__((__vector_size__(16)));
+typedef double W __attribute__((__vector_size__(16)));
+V b;
+W c;
+
+void
+foo (void *p)
+{
+  V e = __builtin_ia32_cvtsd2ss (b, c);
+  V g = e;
+  float f = g[0];
+  __builtin_memcpy (p, &f, sizeof (f));
+}

        Jakub