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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.
This commit is contained in:
Jonathan Wright 2021-10-11 18:37:32 +01:00
parent 8197ab94b4
commit 2fc2026061
1 changed files with 0 additions and 13 deletions
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13
gcc/expr.c
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@ -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);