gcc/expr.c: Remove historic workaround for broken SIMD subreg

A long time ago, using a parallel to take a subreg of a SIMD register
was broken. This temporary fix[1] (from 2003) spilled these registers
to memory and reloaded the appropriate part to obtain the subreg.

The fix initially existed for the benefit of the PowerPC E500 - a
platform for which GCC removed support a number of years ago.
Regardless, a proper mechanism for taking a subreg of a SIMD register
exists now anyway.

This patch removes the workaround thus preventing SIMD registers
being dumped to memory unnecessarily - which sometimes can't be fixed
by later passes.

[1] https://gcc.gnu.org/pipermail/gcc-patches/2003-April/102099.html

gcc/ChangeLog:

2021-10-11  Jonathan Wright  <jonathan.wright@arm.com>

	* expr.c (emit_group_load_1): Remove historic workaround.

diff --git a/gcc/expr.c b/gcc/expr.c
index eb33643..5673902 100644 (file)
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -2508,19 +2508,6 @@ emit_group_load_1 (rtx *tmps, rtx dst, rtx orig_src, tree type,
                                           NULL);
            }
        }
-      /* FIXME: A SIMD parallel will eventually lead to a subreg of a
-        SIMD register, which is currently broken.  While we get GCC
-        to emit proper RTL for these cases, let's dump to memory.  */
-      else if (VECTOR_MODE_P (GET_MODE (dst))
-              && REG_P (src))
-       {
-         poly_uint64 slen = GET_MODE_SIZE (GET_MODE (src));
-         rtx mem;
-
-         mem = assign_stack_temp (GET_MODE (src), slen);
-         emit_move_insn (mem, src);
-         tmps[i] = adjust_address (mem, mode, bytepos);
-       }
       else if (CONSTANT_P (src) && GET_MODE (dst) != BLKmode
                && XVECLEN (dst, 0) > 1)
         tmps[i] = simplify_gen_subreg (mode, src, GET_MODE (dst), bytepos);