Hi All,
This allows copy_blkmode_to_reg to perform larger copies when it is safe to do
so by calculating
the bitsize per iteration doing the maximum copy allowed that does not read more
than the amount of bits left to copy.
Strictly speaking, this copying is only done if:
1. the target supports fast unaligned access
2. no padding is being used.
This should avoid the issues of the first patch (PR85123) but still work for
targets that are safe
to do so.
Original patch https://gcc.gnu.org/ml/gcc-patches/2017-11/msg01088.html
Previous respin https://gcc.gnu.org/ml/gcc-patches/2018-04/msg00239.html
This produces for the copying of a 3 byte structure:
fun3:
adrp x1, .LANCHOR0
add x1, x1, :lo12:.LANCHOR0
mov x0, 0
sub sp, sp, #16
ldrh w2, [x1, 16]
ldrb w1, [x1, 18]
add sp, sp, 16
bfi x0, x2, 0, 16
bfi x0, x1, 16, 8
ret
whereas before it was producing
fun3:
adrp x0, .LANCHOR0
add x2, x0, :lo12:.LANCHOR0
sub sp, sp, #16
ldrh w1, [x0, #:lo12:.LANCHOR0]
ldrb w0, [x2, 2]
strh w1, [sp, 8]
strb w0, [sp, 10]
ldr w0, [sp, 8]
add sp, sp, 16
ret
Cross compiled and regtested on
aarch64_be-none-elf
armeb-none-eabi
and no issues
Boostrapped and regtested
aarch64-none-linux-gnu
x86_64-pc-linux-gnu
powerpc64-unknown-linux-gnu
arm-none-linux-gnueabihf
and found no issues.
OK for trunk?
Thanks,
Tamar
gcc/
2018-07-23 Tamar Christina <tamar.christ...@arm.com>
* expr.c (copy_blkmode_to_reg): Perform larger copies when safe.
--
diff --git a/gcc/expr.c b/gcc/expr.c
index f665e187ebbbc7874ec88e84ca47ed991491c3e5..17b580aabf761491d8003ac74daa014bc252ea9f 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -2763,6 +2763,7 @@ copy_blkmode_to_reg (machine_mode mode_in, tree src)
int i, n_regs;
unsigned HOST_WIDE_INT bitpos, xbitpos, padding_correction = 0, bytes;
unsigned int bitsize;
+ bool slow_unaligned_access;
rtx *dst_words, dst, x, src_word = NULL_RTX, dst_word = NULL_RTX;
/* No current ABI uses variable-sized modes to pass a BLKmnode type. */
fixed_size_mode mode = as_a <fixed_size_mode> (mode_in);
@@ -2795,6 +2796,10 @@ copy_blkmode_to_reg (machine_mode mode_in, tree src)
n_regs = (bytes + UNITS_PER_WORD - 1) / UNITS_PER_WORD;
dst_words = XALLOCAVEC (rtx, n_regs);
+
+ slow_unaligned_access
+ = targetm.slow_unaligned_access (word_mode, TYPE_ALIGN (TREE_TYPE (src)));
+
bitsize = MIN (TYPE_ALIGN (TREE_TYPE (src)), BITS_PER_WORD);
/* Copy the structure BITSIZE bits at a time. */
@@ -2816,6 +2821,23 @@ copy_blkmode_to_reg (machine_mode mode_in, tree src)
emit_move_insn (dst_word, CONST0_RTX (word_mode));
}
+
+ /* Find the largest integer mode that can be used to copy all or as
+ many bits as possible of the structure if the target supports larger
+ copies. There are too many corner cases here w.r.t to alignments on
+ the read/writes. So if there is any padding just use single byte
+ operations. */
+ opt_scalar_int_mode mode_iter;
+ FOR_EACH_MODE_IN_CLASS (mode_iter, MODE_INT)
+ if (padding_correction == 0
+ && !slow_unaligned_access
+ && GET_MODE_BITSIZE (mode_iter.require ())
+ <= ((bytes * BITS_PER_UNIT) - bitpos)
+ && GET_MODE_BITSIZE (mode_iter.require ()) <= BITS_PER_WORD)
+ bitsize = GET_MODE_BITSIZE (mode_iter.require ());
+ else
+ break;
+
/* We need a new source operand each time bitpos is on a word
boundary. */
if (bitpos % BITS_PER_WORD == 0)
