Re: [PATCH 01/13] target/riscv: Really use little endianness for 128-bit loads/stores

[Richard Henderson]

On 10/10/25 08:50, Philippe Mathieu-Daudé wrote:

Per commit a2f827ff4f4 ("target/riscv: accessors to registers upper
part and 128-bit load/store") description:

  > The 128-bit ISA adds ldu, lq and sq. We provide support for these
  > instructions. Note that (a) we compute only 64-bit addresses to
  > actually access memory, cowardly utilizing the existing address
  > translation mechanism of QEMU, and (b) we assume for now
  > little-endian memory accesses.

    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

However this commit used MO_TE (target endianness) for the
gen_load_i128() and gen_store_i128() helpers. Likely it was
unnoticed because current targets are only built using little
endianness:

   $ git grep -L TARGET_BIG_ENDIAN=y configs/targets/riscv*
   configs/targets/riscv32-linux-user.mak
   configs/targets/riscv32-softmmu.mak
   configs/targets/riscv64-bsd-user.mak
   configs/targets/riscv64-linux-user.mak
   configs/targets/riscv64-softmmu.mak

Replace by MO_TE -> MO_LE to really use little endianness.

Cc: Fabien Portas <fabien.por...@grenoble-inp.org>
Cc: Frédéric Pétrot <frederic.pet...@univ-grenoble-alpes.fr>
Fixes: a2f827ff4f4 ("target/riscv: accessors to registers upper part and 128-bit 
load/store")
Signed-off-by: Philippe Mathieu-Daudé <phi...@linaro.org>
---
  target/riscv/insn_trans/trans_rvi.c.inc | 12 ++++++++----
  1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/target/riscv/insn_trans/trans_rvi.c.inc 
b/target/riscv/insn_trans/trans_rvi.c.inc
index b9c71604687..df0b555176a 100644
--- a/target/riscv/insn_trans/trans_rvi.c.inc
+++ b/target/riscv/insn_trans/trans_rvi.c.inc
@@ -389,9 +389,11 @@ static bool gen_load_i128(DisasContext *ctx, arg_lb *a, 
MemOp memop)
          }
      } else {
          /* assume little-endian memory access for now */
-        tcg_gen_qemu_ld_tl(destl, addrl, ctx->mem_idx, MO_TEUQ);
+        MemOp memop = MO_LEUQ;
+
+        tcg_gen_qemu_ld_tl(destl, addrl, ctx->mem_idx, memop);
          tcg_gen_addi_tl(addrl, addrl, 8);
-        tcg_gen_qemu_ld_tl(desth, addrl, ctx->mem_idx, MO_TEUQ);
+        tcg_gen_qemu_ld_tl(desth, addrl, ctx->mem_idx, memop);
      }

gen_set_gpr128(ctx, a->rd, destl, desth);

@@ -494,9 +496,11 @@ static bool gen_store_i128(DisasContext *ctx, arg_sb *a, 
MemOp memop)
          tcg_gen_qemu_st_tl(src2l, addrl, ctx->mem_idx, memop);
      } else {
          /* little-endian memory access assumed for now */
-        tcg_gen_qemu_st_tl(src2l, addrl, ctx->mem_idx, MO_TEUQ);
+        MemOp memop = MO_LEUQ;
+
+        tcg_gen_qemu_st_tl(src2l, addrl, ctx->mem_idx, memop);
          tcg_gen_addi_tl(addrl, addrl, 8);
-        tcg_gen_qemu_st_tl(src2h, addrl, ctx->mem_idx, MO_TEUQ);
+        tcg_gen_qemu_st_tl(src2h, addrl, ctx->mem_idx, memop);
      }
      return true;
  }

We fix this to use tcg_gen_qemu_{ld,st}_i128.


r~