diff mbox series

[5/7] riscv: Use by-pieces to do overlapping accesses in block_move_straight

Message ID 20221113230521.712693-6-christoph.muellner@vrull.eu
State New
Headers
Series riscv: Improve builtins expansion |

Commit Message

Christoph Müllner Nov. 13, 2022, 11:05 p.m. UTC 
  From: Christoph Müllner <christoph.muellner@vrull.eu>

The current implementation of riscv_block_move_straight() emits a couple
of load-store pairs with maximum width (e.g. 8-byte for RV64).
The remainder is handed over to move_by_pieces(), which emits code based
target settings like slow_unaligned_access and overlap_op_by_pieces.

move_by_pieces() will emit overlapping memory accesses with maximum
width only if the given length exceeds the size of one access
(e.g. 15-bytes for 8-byte accesses).

This patch changes the implementation of riscv_block_move_straight()
such, that it preserves a remainder within the interval
[delta..2*delta) instead of [0..delta), so that overlapping memory
access may be emitted (if the requirements for them are given).

gcc/ChangeLog:

	* config/riscv/riscv-string.c (riscv_block_move_straight):
	  Adjust range for emitted load/store pairs.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>
---
 gcc/config/riscv/riscv-string.cc              |  8 ++++----
 .../gcc.target/riscv/memcpy-overlapping.c     | 19 ++++++++-----------
 2 files changed, 12 insertions(+), 15 deletions(-)

Comments

Jeff Law Nov. 14, 2022, 5:16 p.m. UTC | #1 
On 11/13/22 16:05, Christoph Muellner wrote:
> From: Christoph Müllner <christoph.muellner@vrull.eu>
>
> The current implementation of riscv_block_move_straight() emits a couple
> of load-store pairs with maximum width (e.g. 8-byte for RV64).
> The remainder is handed over to move_by_pieces(), which emits code based
> target settings like slow_unaligned_access and overlap_op_by_pieces.
>
> move_by_pieces() will emit overlapping memory accesses with maximum
> width only if the given length exceeds the size of one access
> (e.g. 15-bytes for 8-byte accesses).
>
> This patch changes the implementation of riscv_block_move_straight()
> such, that it preserves a remainder within the interval
> [delta..2*delta) instead of [0..delta), so that overlapping memory
> access may be emitted (if the requirements for them are given).
>
> gcc/ChangeLog:
>
> 	* config/riscv/riscv-string.c (riscv_block_move_straight):
> 	  Adjust range for emitted load/store pairs.

The change to riscv_expand_block_move isn't noted in the ChangeLog.  OK 
with that fixed (I'm assuming you want to attempt to use overlapping 
word ops for that case).


jeff
Christoph Müllner Nov. 14, 2022, 7:01 p.m. UTC | #2 
On Mon, Nov 14, 2022 at 6:16 PM Jeff Law <jeffreyalaw@gmail.com> wrote:

>
> On 11/13/22 16:05, Christoph Muellner wrote:
> > From: Christoph Müllner <christoph.muellner@vrull.eu>
> >
> > The current implementation of riscv_block_move_straight() emits a couple
> > of load-store pairs with maximum width (e.g. 8-byte for RV64).
> > The remainder is handed over to move_by_pieces(), which emits code based
> > target settings like slow_unaligned_access and overlap_op_by_pieces.
> >
> > move_by_pieces() will emit overlapping memory accesses with maximum
> > width only if the given length exceeds the size of one access
> > (e.g. 15-bytes for 8-byte accesses).
> >
> > This patch changes the implementation of riscv_block_move_straight()
> > such, that it preserves a remainder within the interval
> > [delta..2*delta) instead of [0..delta), so that overlapping memory
> > access may be emitted (if the requirements for them are given).
> >
> > gcc/ChangeLog:
> >
> >       * config/riscv/riscv-string.c (riscv_block_move_straight):
> >         Adjust range for emitted load/store pairs.
>
> The change to riscv_expand_block_move isn't noted in the ChangeLog.  OK
> with that fixed (I'm assuming you want to attempt to use overlapping
> word ops for that case).
>

The change in riscv_expand_block_move is a code cleanup.
At the beginning of riscv_expand_block_move we do the following:
  unsigned HOST_WIDE_INT length = UINTVAL (length);
The signature of riscv_block_move_straight wants a "unsigned HOST_WIDE_INT
length".
So we can simply reuse length instead of doing "INTVAL (length)", which is
redundant
and uses the wrong signess (INTVAL vs UINTVAL).

Also, the ChangeLog entry for the test was missing.

Thanks,
Christoph


>
>
> jeff
>
>
>
Jeff Law Nov. 14, 2022, 7:05 p.m. UTC | #3 
On 11/14/22 12:01, Christoph Müllner wrote:
>
>
> On Mon, Nov 14, 2022 at 6:16 PM Jeff Law <jeffreyalaw@gmail.com> wrote:
>
>
>     On 11/13/22 16:05, Christoph Muellner wrote:
>     > From: Christoph Müllner <christoph.muellner@vrull.eu>
>     >
>     > The current implementation of riscv_block_move_straight() emits
>     a couple
>     > of load-store pairs with maximum width (e.g. 8-byte for RV64).
>     > The remainder is handed over to move_by_pieces(), which emits
>     code based
>     > target settings like slow_unaligned_access and overlap_op_by_pieces.
>     >
>     > move_by_pieces() will emit overlapping memory accesses with maximum
>     > width only if the given length exceeds the size of one access
>     > (e.g. 15-bytes for 8-byte accesses).
>     >
>     > This patch changes the implementation of riscv_block_move_straight()
>     > such, that it preserves a remainder within the interval
>     > [delta..2*delta) instead of [0..delta), so that overlapping memory
>     > access may be emitted (if the requirements for them are given).
>     >
>     > gcc/ChangeLog:
>     >
>     >       * config/riscv/riscv-string.c (riscv_block_move_straight):
>     >         Adjust range for emitted load/store pairs.
>
>     The change to riscv_expand_block_move isn't noted in the
>     ChangeLog.  OK
>     with that fixed (I'm assuming you want to attempt to use overlapping
>     word ops for that case).
>
>
> The change in riscv_expand_block_move is a code cleanup.
> At the beginning of riscv_expand_block_move we do the following:
>   unsigned HOST_WIDE_INT length = UINTVAL (length);

AH, missed that.


Thanks,

Jeff
diff mbox series

Patch

diff --git a/gcc/config/riscv/riscv-string.cc b/gcc/config/riscv/riscv-string.cc
index 6882f0be269..1137df475be 100644
--- a/gcc/config/riscv/riscv-string.cc
+++ b/gcc/config/riscv/riscv-string.cc
@@ -57,18 +57,18 @@  riscv_block_move_straight (rtx dest, rtx src, unsigned HOST_WIDE_INT length)
   delta = bits / BITS_PER_UNIT;
 
   /* Allocate a buffer for the temporary registers.  */
-  regs = XALLOCAVEC (rtx, length / delta);
+  regs = XALLOCAVEC (rtx, length / delta - 1);
 
   /* Load as many BITS-sized chunks as possible.  Use a normal load if
      the source has enough alignment, otherwise use left/right pairs.  */
-  for (offset = 0, i = 0; offset + delta <= length; offset += delta, i++)
+  for (offset = 0, i = 0; offset + 2 * delta <= length; offset += delta, i++)
     {
       regs[i] = gen_reg_rtx (mode);
       riscv_emit_move (regs[i], adjust_address (src, mode, offset));
     }
 
   /* Copy the chunks to the destination.  */
-  for (offset = 0, i = 0; offset + delta <= length; offset += delta, i++)
+  for (offset = 0, i = 0; offset + 2 * delta <= length; offset += delta, i++)
     riscv_emit_move (adjust_address (dest, mode, offset), regs[i]);
 
   /* Mop up any left-over bytes.  */
@@ -166,7 +166,7 @@  riscv_expand_block_move (rtx dest, rtx src, rtx length)
 
       if (hwi_length <= (RISCV_MAX_MOVE_BYTES_STRAIGHT / factor))
 	{
-	  riscv_block_move_straight (dest, src, INTVAL (length));
+	  riscv_block_move_straight (dest, src, hwi_length);
 	  return true;
 	}
       else if (optimize && align >= BITS_PER_WORD)
diff --git a/gcc/testsuite/gcc.target/riscv/memcpy-overlapping.c b/gcc/testsuite/gcc.target/riscv/memcpy-overlapping.c
index ffb7248bfd1..ef95bfb879b 100644
--- a/gcc/testsuite/gcc.target/riscv/memcpy-overlapping.c
+++ b/gcc/testsuite/gcc.target/riscv/memcpy-overlapping.c
@@ -25,26 +25,23 @@  COPY_N(15)
 /* Emits 2x {ld,sd} and 1x {lw,sw}.  */
 COPY_N(19)
 
-/* Emits 3x ld and 3x sd.  */
+/* Emits 3x {ld,sd}.  */
 COPY_N(23)
 
 /* The by-pieces infrastructure handles up to 24 bytes.
    So the code below is emitted via cpymemsi/block_move_straight.  */
 
-/* Emits 3x {ld,sd} and 1x {lhu,lbu,sh,sb}.  */
+/* Emits 3x {ld,sd} and 1x {lw,sw}.  */
 COPY_N(27)
 
-/* Emits 3x {ld,sd} and 1x {lw,lbu,sw,sb}.  */
+/* Emits 4x {ld,sd}.  */
 COPY_N(29)
 
-/* Emits 3x {ld,sd} and 2x {lw,sw}.  */
+/* Emits 4x {ld,sd}.  */
 COPY_N(31)
 
-/* { dg-final { scan-assembler-times "ld\t" 21 } } */
-/* { dg-final { scan-assembler-times "sd\t" 21 } } */
+/* { dg-final { scan-assembler-times "ld\t" 23 } } */
+/* { dg-final { scan-assembler-times "sd\t" 23 } } */
 
-/* { dg-final { scan-assembler-times "lw\t" 5 } } */
-/* { dg-final { scan-assembler-times "sw\t" 5 } } */
-
-/* { dg-final { scan-assembler-times "lbu\t" 2 } } */
-/* { dg-final { scan-assembler-times "sb\t" 2 } } */
+/* { dg-final { scan-assembler-times "lw\t" 3 } } */
+/* { dg-final { scan-assembler-times "sw\t" 3 } } */