Re: [PATCH] LoongArch: Use LSX and LASX for block move

[chenglulu]

Hi,RuoYao:

 I think the test example memcpy-vec-3.c submitted in r14-3818 is 
implemented incorrectly.

The 16-byte length in this test example will cause can_move_by_pieces to 
return true when with '-mstrict-align', so no vector load instructions 
will be generated.

在 2023/9/8 上午12:14, Xi Ruoyao 写道:
gcc/ChangeLog:

        * config/loongarch/loongarch.h (LARCH_MAX_MOVE_PER_INSN):
        Define to the maximum amount of bytes able to be loaded or
        stored with one machine instruction.
        * config/loongarch/loongarch.cc (loongarch_mode_for_move_size):
        New static function.
        (loongarch_block_move_straight): Call
        loongarch_mode_for_move_size for machine_mode to be moved.
        (loongarch_expand_block_move): Use LARCH_MAX_MOVE_PER_INSN
        instead of UNITS_PER_WORD.
---

Bootstrapped and regtested on loongarch64-linux-gnu, with PR110939 patch
applied, the "lib_build_self_spec = %<..." line in t-linux commented out
(because it's silently making -mlasx in BOOT_CFLAGS ineffective, Yujie
is working on a proper fix), and BOOT_CFLAGS="-O3 -mlasx".  Ok for trunk?

  gcc/config/loongarch/loongarch.cc | 22 ++++++++++++++++++----
  gcc/config/loongarch/loongarch.h  |  3 +++
  2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/gcc/config/loongarch/loongarch.cc 
b/gcc/config/loongarch/loongarch.cc
index 6698414281e..509ef2b97f1 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -5191,6 +5191,20 @@ loongarch_function_ok_for_sibcall (tree decl 
ATTRIBUTE_UNUSED,
    return true;
  }
  
+static machine_mode
+loongarch_mode_for_move_size (HOST_WIDE_INT size)
+{
+  switch (size)
+    {
+    case 32:
+      return V32QImode;
+    case 16:
+      return V16QImode;
+    }
+
+  return int_mode_for_size (size * BITS_PER_UNIT, 0).require ();
+}
+
  /* Emit straight-line code to move LENGTH bytes from SRC to DEST.
     Assume that the areas do not overlap.  */
  
@@ -5220,7 +5234,7 @@ loongarch_block_move_straight (rtx dest, rtx src, HOST_WIDE_INT length,
  
    for (delta_cur = delta, i = 0, offs = 0; offs < length; delta_cur /= 2)
      {
-      mode = int_mode_for_size (delta_cur * BITS_PER_UNIT, 0).require ();
+      mode = loongarch_mode_for_move_size (delta_cur);
  
        for (; offs + delta_cur <= length; offs += delta_cur, i++)
        {
@@ -5231,7 +5245,7 @@ loongarch_block_move_straight (rtx dest, rtx src, 
HOST_WIDE_INT length,
  
    for (delta_cur = delta, i = 0, offs = 0; offs < length; delta_cur /= 2)
      {
-      mode = int_mode_for_size (delta_cur * BITS_PER_UNIT, 0).require ();
+      mode = loongarch_mode_for_move_size (delta_cur);
  
        for (; offs + delta_cur <= length; offs += delta_cur, i++)
        loongarch_emit_move (adjust_address (dest, mode, offs), regs[i]);
@@ -5326,8 +5340,8 @@ loongarch_expand_block_move (rtx dest, rtx src, rtx 
r_length, rtx r_align)
  
    HOST_WIDE_INT align = INTVAL (r_align);
  
-  if (!TARGET_STRICT_ALIGN || align > UNITS_PER_WORD)
-    align = UNITS_PER_WORD;
+  if (!TARGET_STRICT_ALIGN || align > LARCH_MAX_MOVE_PER_INSN)
+    align = LARCH_MAX_MOVE_PER_INSN;
  
    if (length <= align * LARCH_MAX_MOVE_OPS_STRAIGHT)
      {
diff --git a/gcc/config/loongarch/loongarch.h b/gcc/config/loongarch/loongarch.h
index 3fc9dc43ab1..7e391205583 100644
--- a/gcc/config/loongarch/loongarch.h
+++ b/gcc/config/loongarch/loongarch.h
@@ -1181,6 +1181,9 @@ typedef struct {
     least twice.  */
  #define LARCH_MAX_MOVE_OPS_STRAIGHT (LARCH_MAX_MOVE_OPS_PER_LOOP_ITER * 2)
  
+#define LARCH_MAX_MOVE_PER_INSN \
+  (ISA_HAS_LASX ? 32 : (ISA_HAS_LSX ? 16 : UNITS_PER_WORD))
+
  /* The base cost of a memcpy call, for MOVE_RATIO and friends.  These
     values were determined experimentally by benchmarking with CSiBE.
  */