[PATCH] Fix expansion ICE on stores into parts of hard registers (PR middle-end/80173)

[Jakub Jelinek]

Hi!

On some arches like x86_64 we allow some aggregates in named register
variables.  If those registers are wider than word, store_bit_field_1
was assuming it must be multiple registers and attempted to pick
a word sized subregister of it, which is fine for pseudos, but if the
destination is a hard register, sometimes such subreg will fail.
If it is a hard register and we know that its mode means a single
register (otherwise we wouldn't allow creating a named register variable for
it), then that subreg is certainly counter-productive, we just want to store
into the whole register.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-03-30  Jakub Jelinek  <ja...@redhat.com>

        PR middle-end/80173
        * expmed.c (store_bit_field_1): Don't attempt to create
        a word subreg out of hard registers wider than word if they
        have HARD_REGNO_NREGS of 1 for their mode.

        * gcc.target/i386/pr80173.c: New test.

--- gcc/expmed.c.jj     2017-01-01 12:45:39.000000000 +0100
+++ gcc/expmed.c        2017-03-30 14:51:01.814449691 +0200
@@ -965,8 +965,14 @@ store_bit_field_1 (rtx str_rtx, unsigned
     }
 
   /* If OP0 is a multi-word register, narrow it to the affected word.
-     If the region spans two words, defer to store_split_bit_field.  */
-  if (!MEM_P (op0) && GET_MODE_SIZE (GET_MODE (op0)) > UNITS_PER_WORD)
+     If the region spans two words, defer to store_split_bit_field.
+     Don't do this if op0 is a single hard register wider than word
+     such as a float or vector register.  */
+  if (!MEM_P (op0)
+      && GET_MODE_SIZE (GET_MODE (op0)) > UNITS_PER_WORD
+      && (!REG_P (op0)
+         || !HARD_REGISTER_P (op0)
+         || HARD_REGNO_NREGS (REGNO (op0), GET_MODE (op0)) != 1))
     {
       if (bitnum % BITS_PER_WORD + bitsize > BITS_PER_WORD)
        {
--- gcc/testsuite/gcc.target/i386/pr80173.c.jj  2017-03-30 15:05:49.600889474 
+0200
+++ gcc/testsuite/gcc.target/i386/pr80173.c     2017-03-30 15:05:33.000000000 
+0200
@@ -0,0 +1,22 @@
+/* PR middle-end/80173 */
+/* { dg-do compile { target lp64 } } */
+/* { dg-options "-O2 -ffixed-xmm7" } */
+
+typedef int V __attribute__ ((vector_size (2 * sizeof (int))));
+
+struct U { V a; V b; };
+
+int
+foo (int i)
+{
+  register struct U u asm ("xmm7") = {{-1, 0}, {-1, 0}};
+  return u.b[i];
+}
+
+int
+bar (int i)
+{
+  register struct U u asm ("xmm7");
+  u = (struct U) {{-1, 0}, {-1, 0}};
+  return u.b[i];
+}

        Jakub