[gcc r17-3488] RISC-V: Remove obsolete CACHE_ALIGNED_STD fusion

https://gcc.gnu.org/g:1beab80079e26aac82c62452dd9217caae226c7c

commit r17-3488-g1beab80079e26aac82c62452dd9217caae226c7c
Author: Jin Ma <[email protected]>
Date:   Wed Aug 12 15:27:18 2026 +0800

    RISC-V: Remove obsolete CACHE_ALIGNED_STD fusion
    
    CACHE_ALIGNED_STD modeled a Veyron V1 store-commit optimization.  That
    design will not reach silicon and no upstream tune enables the fusion.
    Remove the specialized recognizer and its unused flag.
    
    gcc/ChangeLog:
    
            * config/riscv/riscv-fusion.cc (riscv_fuse_cache_aligned_std):
            Remove.
            (riscv_fusion_table): Remove its entry.
            * config/riscv/riscv-protos.h (enum riscv_fusion_pairs): Remove
            RISCV_FUSE_CACHE_ALIGNED_STD.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/riscv/fusion-cache-aligned-std.c: Remove.
    
    Signed-off-by: Jin Ma <[email protected]>

Diff:
---
 gcc/config/riscv/riscv-fusion.cc                   | 65 ----------------------
 gcc/config/riscv/riscv-protos.h                    |  7 +--
 .../gcc.target/riscv/fusion-cache-aligned-std.c    | 21 -------
 3 files changed, 3 insertions(+), 90 deletions(-)

diff --git a/gcc/config/riscv/riscv-fusion.cc b/gcc/config/riscv/riscv-fusion.cc
index ca4de9dfc9eb..2ce9b9659745 100644
--- a/gcc/config/riscv/riscv-fusion.cc
+++ b/gcc/config/riscv/riscv-fusion.cc
@@ -561,69 +561,6 @@ riscv_fuse_auipc_ld (rtx_insn *prev, rtx_insn *curr)
   return false;
 }
 
-/* Check for RISCV_FUSE_CACHE_ALIGNED_STD fusion.
-   prev (sd) == (set (mem:DI (rs1, offset1)) (reg:DI rs2))
-   curr (sd) == (set (mem:DI (rs1, offset2)) (reg:DI rs3))
-
-   Constraints:
-     rs1 has at least 128-bit pointer alignment
-     min (offset1, offset2) is 16-byte aligned
-     abs (offset1 - offset2) == 8.  */
-
-static bool
-riscv_fuse_cache_aligned_std (rtx_insn *prev, rtx_insn *curr)
-{
-  rtx prev_set = single_set (prev);
-  rtx curr_set = single_set (curr);
-  if (!prev_set || !curr_set || any_condjump_p (curr))
-    return false;
-
-  if (MEM_P (SET_DEST (prev_set))
-      && MEM_P (SET_DEST (curr_set))
-      && SCALAR_INT_MODE_P (GET_MODE (SET_DEST (curr_set)))
-      /* We can probably relax this condition.  The documentation is a bit
-	 unclear about sub-word cases.  So we just model DImode for now.  */
-      && GET_MODE (SET_DEST (curr_set)) == DImode
-      && GET_MODE (SET_DEST (prev_set)) == DImode)
-    {
-      rtx base_prev, base_curr, offset_prev, offset_curr;
-
-      extract_base_offset_in_addr (SET_DEST (prev_set),
-				   &base_prev, &offset_prev);
-      extract_base_offset_in_addr (SET_DEST (curr_set),
-				   &base_curr, &offset_curr);
-
-      /* Proceed only if we find both bases, both bases are register and
-	 bases are the same register.  */
-      if (base_prev != NULL_RTX && base_curr != NULL_RTX
-	  && REG_P (base_prev) && REG_P (base_curr)
-	  && REGNO (base_prev) == REGNO (base_curr)
-	  /* The alignment of the base pointer is more useful than the
-	     alignment of the memory reference for determining if we're
-	     on opposite sides of a cache line.  */
-	  && REGNO_POINTER_ALIGN (ORIGINAL_REGNO (base_prev)) >= 128)
-	{
-	  /* The two stores must be contained within opposite halves of
-	     the same 16 byte aligned block of memory.  We know the
-	     pointer has suitable alignment, so we just need to check
-	     the offsets of the two stores for suitable alignment.  */
-
-	  /* Get the smaller offset into OFFSET_PREV.  */
-	  if (INTVAL (offset_prev) > INTVAL (offset_curr))
-	    std::swap (offset_prev, offset_curr);
-
-	  /* We have a match if the smaller offset (OFFSET_PREV) is 16
-	     byte aligned and the higher offset is 8 bytes more than
-	     the lower offset.  */
-	  if ((INTVAL (offset_prev) % 16) == 0
-	      && (INTVAL (offset_prev) + 8 == INTVAL (offset_curr)))
-	    return true;
-	}
-    }
-
-  return false;
-}
-
 /* Check for RISCV_FUSE_ALIGNED_STD fusion.
    prev (store) == (set (mem (rs1, offset1)) (reg rs2))
    curr (store) == (set (mem (rs1, offset2)) (reg rs3))
@@ -850,8 +787,6 @@ static const struct riscv_fusion_entry riscv_fusion_table[] =
     riscv_fuse_lui_ld, "RISCV_FUSE_LUI_LD" },
   { RISCV_FUSE_AUIPC_LD,
     riscv_fuse_auipc_ld, "RISCV_FUSE_AUIPC_LD" },
-  { RISCV_FUSE_CACHE_ALIGNED_STD,
-    riscv_fuse_cache_aligned_std, "RISCV_FUSE_CACHE_ALIGNED_STD" },
   { RISCV_FUSE_ALIGNED_STD,
     riscv_fuse_aligned_std, "RISCV_FUSE_ALIGNED_STD" },
   { RISCV_FUSE_BFEXT,
diff --git a/gcc/config/riscv/riscv-protos.h b/gcc/config/riscv/riscv-protos.h
index f23aeacf895e..e9612cca1a1d 100644
--- a/gcc/config/riscv/riscv-protos.h
+++ b/gcc/config/riscv/riscv-protos.h
@@ -863,10 +863,9 @@ enum riscv_fusion_pairs
   RISCV_FUSE_AUIPC_LD = HOST_WIDE_INT_1U << 7,
   RISCV_FUSE_LDPREINCREMENT = HOST_WIDE_INT_1U << 8,
   RISCV_FUSE_ALIGNED_STD = HOST_WIDE_INT_1U << 9,
-  RISCV_FUSE_CACHE_ALIGNED_STD = HOST_WIDE_INT_1U << 10,
-  RISCV_FUSE_BFEXT = HOST_WIDE_INT_1U << 11,
-  RISCV_FUSE_EXPANDED_LD = HOST_WIDE_INT_1U << 12,
-  RISCV_FUSE_B_ALUI = HOST_WIDE_INT_1U << 13,
+  RISCV_FUSE_BFEXT = HOST_WIDE_INT_1U << 10,
+  RISCV_FUSE_EXPANDED_LD = HOST_WIDE_INT_1U << 11,
+  RISCV_FUSE_B_ALUI = HOST_WIDE_INT_1U << 12,
 };
 
 extern bool riscv_macro_fusion_p (void);
diff --git a/gcc/testsuite/gcc.target/riscv/fusion-cache-aligned-std.c b/gcc/testsuite/gcc.target/riscv/fusion-cache-aligned-std.c
deleted file mode 100644
index 5484e0c05758..000000000000
--- a/gcc/testsuite/gcc.target/riscv/fusion-cache-aligned-std.c
+++ /dev/null
@@ -1,21 +0,0 @@
-/* Verify RISCV_FUSE_CACHE_ALIGNED_STD correctly matches consecutive
-   stores to the same cache line.  This exercises the fix for base
-   register comparison (changed from != to ==).  */
-/* { dg-do compile } */
-/* { dg-skip-if "" { *-*-* } { "-O0" "-O1" "-Og" "-Os" "-Oz" "-flto" } } */
-/* { dg-options "-march=rv64gc -mabi=lp64d -mtune=sifive-p600-series -fdump-rtl-sched1" } */
-/* No upstream mtune currently enables RISCV_FUSE_CACHE_ALIGNED_STD.  */
-/* { dg-final { scan-rtl-dump "RISCV_FUSE_CACHE_ALIGNED_STD" "sched1" { xfail *-*-* } } } */
-
-struct pair
-{
-  long a;
-  long b;
-} __attribute__ ((aligned (16)));
-
-void
-store_pair (struct pair *p, long x, long y)
-{
-  p->a = x;
-  p->b = y;
-}