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Re: [Qemu-ppc] [PATCH 2/2] PPC: e500: Merge 32 and 64 bit SPE emulation

From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH 2/2] PPC: e500: Merge 32 and 64 bit SPE emulation
Date: Wed, 04 Jun 2014 23:51:21 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.5.0

On 04.06.14 23:38, Richard Henderson wrote:
On 06/04/2014 02:09 PM, Alexander Graf wrote:
@@ -9030,13 +8820,10 @@ static inline void gen_evmwumi(DisasContext *ctx)
      t1 = tcg_temp_new_i64();
/* t0 := rA; t1 := rB */
-#if defined(TARGET_PPC64)
-    tcg_gen_ext32u_tl(t0, cpu_gpr[rA(ctx->opcode)]);
-    tcg_gen_ext32u_tl(t1, cpu_gpr[rB(ctx->opcode)]);
      tcg_gen_extu_tl_i64(t0, cpu_gpr[rA(ctx->opcode)]);
+    tcg_gen_ext32u_i64(t0, t0);
Better in one step:

  tcg_gen_ext32u_i64(t0, cpu_gpr[rA(ctx->opcode)]);

But cpu_gpr can be i32 for qemu-system-ppc, no?

@@ -9112,13 +8899,10 @@ static inline void gen_evmwsmi(DisasContext *ctx)
      t1 = tcg_temp_new_i64();
/* t0 := rA; t1 := rB */
+    tcg_gen_extu_tl_i64(t0, cpu_gpr[rA(ctx->opcode)]);
+    tcg_gen_ext32s_i64(t0, t0);
+    tcg_gen_extu_tl_i64(t1, cpu_gpr[rB(ctx->opcode)]);
+    tcg_gen_ext32s_i64(t1, t1);

Although I do wonder about using the actual 32-bit widening multiply
primitives: tcg_gen_mulu2_i32 / tcg_gen_muls2_i32.

I suspect the optimizer would clean up the unsigned version, but it hasn't got
a chance with the signed version.

I personally don't really care too much about SPE performance - anything that doesn't fail works for me ;).

Otherwise, it looks ok.

Thanks a lot for looking through it!


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