From: Richard Henderson <richard.henderson@linaro.org>

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20190215100058.20015-8-mark.cave-ayland@ilande.co.uk>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 target/ppc/translate/vsx-impl.inc.c | 36 +++++++++--------------------
 1 file changed, 11 insertions(+), 25 deletions(-)

diff --git a/target/ppc/translate/vsx-impl.inc.c b/target/ppc/translate/vsx-impl.inc.c
index 944fc0608a..0e8cecb00a 100644
--- a/target/ppc/translate/vsx-impl.inc.c
+++ b/target/ppc/translate/vsx-impl.inc.c
@@ -1359,38 +1359,24 @@ static void gen_xxsel(DisasContext * ctx)
 
 static void gen_xxspltw(DisasContext *ctx)
 {
-    TCGv_i64 b, b2;
-    TCGv_i64 vsr;
+    int rt = xT(ctx->opcode);
+    int rb = xB(ctx->opcode);
+    int uim = UIM(ctx->opcode);
+    int tofs, bofs;
 
     if (unlikely(!ctx->vsx_enabled)) {
         gen_exception(ctx, POWERPC_EXCP_VSXU);
         return;
     }
 
-    vsr = tcg_temp_new_i64();
-    if (UIM(ctx->opcode) & 2) {
-        get_cpu_vsrl(vsr, xB(ctx->opcode));
-    } else {
-        get_cpu_vsrh(vsr, xB(ctx->opcode));
-    }
-
-    b = tcg_temp_new_i64();
-    b2 = tcg_temp_new_i64();
-
-    if (UIM(ctx->opcode) & 1) {
-        tcg_gen_ext32u_i64(b, vsr);
-    } else {
-        tcg_gen_shri_i64(b, vsr, 32);
-    }
-
-    tcg_gen_shli_i64(b2, b, 32);
-    tcg_gen_or_i64(vsr, b, b2);
-    set_cpu_vsrh(xT(ctx->opcode), vsr);
-    set_cpu_vsrl(xT(ctx->opcode), vsr);
+    tofs = vsr_full_offset(rt);
+    bofs = vsr_full_offset(rb);
+    bofs += uim << MO_32;
+#ifndef HOST_WORDS_BIG_ENDIAN
+    bofs ^= 8 | 4;
+#endif
 
-    tcg_temp_free_i64(vsr);
-    tcg_temp_free_i64(b);
-    tcg_temp_free_i64(b2);
+    tcg_gen_gvec_dup_mem(MO_32, tofs, bofs, 16, 16);
 }
 
 #define pattern(x) (((x) & 0xff) * (~(uint64_t)0 / 0xff))
-- 
2.20.1

On Mon, 18 Feb 2019 at 14:31, David Gibson <david@gibson.dropbear.id.au> wrote:
>
> From: Richard Henderson <richard.henderson@linaro.org>
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> Acked-by: David Gibson <david@gibson.dropbear.id.au>
> Message-Id: <20190215100058.20015-8-mark.cave-ayland@ilande.co.uk>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

So this is a commit from 18 months back, but I happened
to notice an oddity in it while grepping the code base for
something else:

> diff --git a/target/ppc/translate/vsx-impl.inc.c b/target/ppc/translate/vsx-impl.inc.c
> index 944fc0608a..0e8cecb00a 100644
> --- a/target/ppc/translate/vsx-impl.inc.c
> +++ b/target/ppc/translate/vsx-impl.inc.c
> @@ -1359,38 +1359,24 @@ static void gen_xxsel(DisasContext * ctx)
>
>  static void gen_xxspltw(DisasContext *ctx)
>  {
> -    TCGv_i64 b, b2;
> -    TCGv_i64 vsr;
> +    int rt = xT(ctx->opcode);
> +    int rb = xB(ctx->opcode);
> +    int uim = UIM(ctx->opcode);
> +    int tofs, bofs;

[...]

> -    tcg_gen_shli_i64(b2, b, 32);
> -    tcg_gen_or_i64(vsr, b, b2);
> -    set_cpu_vsrh(xT(ctx->opcode), vsr);
> -    set_cpu_vsrl(xT(ctx->opcode), vsr);
> +    tofs = vsr_full_offset(rt);
> +    bofs = vsr_full_offset(rb);
> +    bofs += uim << MO_32;
> +#ifndef HOST_WORDS_BIG_ENDIAN
> +    bofs ^= 8 | 4;
> +#endif

The ifdef is HOST_WORDS_BIGENDIAN without the
third underscore, so this XOR operation will be
done on both little and big-endian hosts.

Should the ifndef line be fixed, or is this actually
a case where the xor really should be done on all hosts
so we should drop the ifndef/endif lines?

>
> -    tcg_temp_free_i64(vsr);
> -    tcg_temp_free_i64(b);
> -    tcg_temp_free_i64(b2);
> +    tcg_gen_gvec_dup_mem(MO_32, tofs, bofs, 16, 16);
>  }

thanks
-- PMM

On 11/6/20 10:47 AM, Peter Maydell wrote:
>> +#ifndef HOST_WORDS_BIG_ENDIAN
>> +    bofs ^= 8 | 4;
>> +#endif
> 
> The ifdef is HOST_WORDS_BIGENDIAN without the
> third underscore, so this XOR operation will be
> done on both little and big-endian hosts.

Ho hum.

> Should the ifndef line be fixed...

This.

I once had a patch set that changed all of our endian tests from defined/undef
to true/false, so that we could detect errors like this.  Perhaps I'll try to
recreate it next dev cycle...


r~