Backported patch to 4.7 branch

[Jakub Jelinek]

Hi!

I've bootstrapped/regtested on x86_64-linux and i686-linux and committed the
following backport to 4.7 branch.

2012-08-13  Jakub Jelinek  <ja...@redhat.com>

        Backported from trunk
        2012-07-19  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/53942
        * function.c (assign_parm_setup_reg): Avoid zero/sign extension
        directly from likely spilled non-fixed hard registers, move them
        to pseudo first.

        * gcc.dg/pr53942.c: New test.

--- gcc/function.c      (revision 189680)
+++ gcc/function.c      (revision 189681)
@@ -2987,11 +2987,26 @@ assign_parm_setup_reg (struct assign_par
          && insn_operand_matches (icode, 1, op1))
        {
          enum rtx_code code = unsignedp ? ZERO_EXTEND : SIGN_EXTEND;
-         rtx insn, insns;
+         rtx insn, insns, t = op1;
          HARD_REG_SET hardregs;
 
          start_sequence ();
-         insn = gen_extend_insn (op0, op1, promoted_nominal_mode,
+         /* If op1 is a hard register that is likely spilled, first
+            force it into a pseudo, otherwise combiner might extend
+            its lifetime too much.  */
+         if (GET_CODE (t) == SUBREG)
+           t = SUBREG_REG (t);
+         if (REG_P (t)
+             && HARD_REGISTER_P (t)
+             && ! TEST_HARD_REG_BIT (fixed_reg_set, REGNO (t))
+             && targetm.class_likely_spilled_p (REGNO_REG_CLASS (REGNO (t))))
+           {
+             t = gen_reg_rtx (GET_MODE (op1));
+             emit_move_insn (t, op1);
+           }
+         else
+           t = op1;
+         insn = gen_extend_insn (op0, t, promoted_nominal_mode,
                                  data->passed_mode, unsignedp);
          emit_insn (insn);
          insns = get_insns ();
--- gcc/testsuite/gcc.dg/pr53942.c      (revision 0)
+++ gcc/testsuite/gcc.dg/pr53942.c      (revision 189681)
@@ -0,0 +1,34 @@
+/* PR rtl-optimization/53942 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-additional-options "-mtune=pentium2" { target { { i?86-*-* x86_64-*-* 
} && ia32 } } } */
+
+struct S
+{
+  unsigned short w[3];
+  unsigned int x, y;
+};
+
+struct S *baz (void);
+
+__attribute__ ((noinline))
+static unsigned char
+foo (struct S *x, unsigned char y)
+{
+  unsigned char c = 0;
+  unsigned char v = x->w[0];
+  c |= v;
+  v = ((x->w[1]) & (1 << y)) ? 1 : 0;
+  c |= v << 1;
+  v = ((x->w[2]) & 0xff) & (1 << y);
+  c |= v << 2;
+  return c;
+}
+
+void
+bar (void)
+{
+  struct S *s = baz ();
+  s->x = foo (s, 6);
+  s->y = foo (s, 7);
+}

        Jakub