Re: [PATCH] target/mips: Remove unreachable 32-bit code on 64-bit Loongson Ext

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 26/10/24 12:45, Philippe Mathieu-Daudé wrote:
> Loongson fixed-point multiplies and divisions opcodes are
> specific to 64-bit cores (Loongson-2 and Loongson-3 families).
> Simplify by removing the 32-bit checks.
> 
> Reported-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> Based-on: <20230831203024.87300-1-philmd@linaro.org>
> ---
>   target/mips/tcg/loong_translate.c | 43 +++----------------------------
>   target/mips/tcg/translate.c       |  2 +-
>   target/mips/tcg/meson.build       |  2 +-
>   3 files changed, 6 insertions(+), 41 deletions(-)


> @@ -295,6 +258,8 @@ static bool trans_DMULTu_G(DisasContext *s, arg_muldiv *a)
>   
>   bool decode_ext_loongson(DisasContext *ctx, uint32_t insn)
>   {
> +    assert(ctx->hflags & MIPS_HFLAG_64);
> +
>       if ((ctx->insn_flags & INSN_LOONGSON2E)
>               && decode_godson2(ctx, ctx->opcode)) {
>           return true;
> diff --git a/target/mips/tcg/translate.c b/target/mips/tcg/translate.c
> index 9839575247e..68a5c21bb2d 100644
> --- a/target/mips/tcg/translate.c
> +++ b/target/mips/tcg/translate.c
> @@ -15020,7 +15020,7 @@ static void decode_opc(CPUMIPSState *env, DisasContext *ctx)
>       if (cpu_supports_isa(env, INSN_VR54XX) && decode_ext_vr54xx(ctx, ctx->opcode)) {
>           return;
>       }
> -    if (decode_ext_loongson(ctx, ctx->opcode)) {
> +    if (TARGET_LONG_BITS == 64 && decode_ext_loongson(ctx, ctx->opcode)) {
>           return;
>       }

Thinking of single binary, better is to extract decode_running_64bit()
and check as runtime; IOW squash:

-- >8 --
diff --git a/target/mips/tcg/translate.h b/target/mips/tcg/translate.h
index 36f3396477a..aa70f27fbba 100644
--- a/target/mips/tcg/translate.h
+++ b/target/mips/tcg/translate.h
@@ -219,0 +220,2 @@ bool decode_ase_mxu(DisasContext *ctx, uint32_t insn);
+bool decode_running_64bit(DisasContext *ctx);
+
diff --git a/target/mips/tcg/translate.c b/target/mips/tcg/translate.c
index 68a5c21bb2d..67480106226 100644
--- a/target/mips/tcg/translate.c
+++ b/target/mips/tcg/translate.c
@@ -1617,0 +1618,5 @@ static inline void check_ps(DisasContext *ctx)
+bool decode_running_64bit(DisasContext *ctx)
+{
+    return ctx->hflags & MIPS_HFLAG_64;
+}
+
@@ -1624 +1629 @@ void check_mips_64(DisasContext *ctx)
-    if (unlikely((TARGET_LONG_BITS != 64) || !(ctx->hflags & 
MIPS_HFLAG_64))) {
+    if (unlikely((TARGET_LONG_BITS != 64) || !decode_running_64bit(ctx))) {
@@ -15023 +15028 @@ static void decode_opc(CPUMIPSState *env, 
DisasContext *ctx)
-    if (TARGET_LONG_BITS == 64 && decode_ext_loongson(ctx, ctx->opcode)) {
+    if (decode_running_64bit(ctx) && decode_ext_loongson(ctx, 
ctx->opcode)) {
diff --git a/target/mips/tcg/meson.build b/target/mips/tcg/meson.build
index fd91148df74..fbb6d6eb407 100644
--- a/target/mips/tcg/meson.build
+++ b/target/mips/tcg/meson.build
@@ -18,0 +19 @@ mips_ss.add(files(
+  'loong_translate.c',
@@ -33 +33,0 @@ mips_ss.add(when: 'TARGET_MIPS64', if_true: files(
-  'loong_translate.c',
---