[gcc r16-5505] LoongArch: extract the base address to promote the combine of RTX.

[LuluCheng]

https://gcc.gnu.org/g:799ca4cda74dec3d567f2c6f417ab09cb53b5025

commit r16-5505-g799ca4cda74dec3d567f2c6f417ab09cb53b5025
Author: zhaozhou <zhaozhou@loongson.cn>
Date:   Fri Nov 14 11:05:08 2025 +0800

    LoongArch: extract the base address to promote the combine of RTX.
    
    When use 256 bits vec for move src to dest, extract the base address
    what plus operation to promote the combine of RTX.
    
    gcc/ChangeLog:
    
            * config/loongarch/loongarch.cc: Extract plus operation.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/loongarch/vector/lasx/lasx-struct-move.c: New test.

Diff:
---
 gcc/config/loongarch/loongarch.cc                       | 10 ++++++++++
 .../gcc.target/loongarch/vector/lasx/lasx-struct-move.c | 17 +++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
index d85932429d04..c1a53e3e7ca0 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -6087,6 +6087,16 @@ loongarch_block_move_straight (rtx dest, rtx src, HOST_WIDE_INT length,
   /* Allocate a buffer for the temporary registers.  */
   regs = XALLOCAVEC (rtx, num_reg);
 
+  /* Extract the base address what plus operation to promote the combine of
+     RTX.  */
+  if (GET_CODE (XEXP (dest, 0)) == PLUS)
+    {
+      unsigned int dest_align = MEM_ALIGN (dest);
+      rtx dest_reg = copy_addr_to_reg (XEXP (dest, 0));
+      dest = change_address (dest, BLKmode, dest_reg);
+      set_mem_align (dest, dest_align);
+    }
+
   for (delta_cur = delta, i = 0, offs = 0; offs < length; delta_cur /= 2)
     {
       mode = loongarch_mode_for_move_size (delta_cur);
diff --git a/gcc/testsuite/gcc.target/loongarch/vector/lasx/lasx-struct-move.c b/gcc/testsuite/gcc.target/loongarch/vector/lasx/lasx-struct-move.c
new file mode 100644
index 000000000000..ca10e9f47a64
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/vector/lasx/lasx-struct-move.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -lasx" } */
+
+struct vec
+{
+  int vec_a[32];
+  double vec_b[5];
+  char vec_c[32];
+};
+
+void
+foo (struct vec *dest, struct vec *src, int index)
+{
+  dest[index] = *src;
+}
+
+/* { dg-final { scan-assembler-times "alsl\.d" 3} } */