[4/4] target/ppc: Rework store conditional to avoid branch

Commit Message

Nicholas Piggin June 4, 2023, 10:28 a.m. UTC

Rework store conditional to avoid a branch in the success case.
Change some of the variable names and layout while here so
gen_conditional_store more closely matches gen_stqcx_.

Signed-off-by: Nicholas Piggin <[e-mail]>
---
 target/ppc/translate.c | 65 ++++++++++++++++++++----------------------
 1 file changed, 31 insertions(+), 34 deletions(-)

Comments

Richard Henderson June 4, 2023, 4:22 p.m. UTC | #1

On 6/4/23 03:28, Nicholas Piggin wrote:
> Rework store conditional to avoid a branch in the success case.
> Change some of the variable names and layout while here so
> gen_conditional_store more closely matches gen_stqcx_.
> 
> Signed-off-by: Nicholas Piggin <[e-mail]>
> ---
>   target/ppc/translate.c | 65 ++++++++++++++++++++----------------------
>   1 file changed, 31 insertions(+), 34 deletions(-)
> 
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 77e1c5abb6..cf99e961f7 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -3812,31 +3812,32 @@ static void gen_stdat(DisasContext *ctx)
>   
>   static void gen_conditional_store(DisasContext *ctx, MemOp memop)
>   {
> -    TCGLabel *l1 = gen_new_label();
> -    TCGLabel *l2 = gen_new_label();
> -    TCGv t0 = tcg_temp_new();
> -    int reg = rS(ctx->opcode);
> +    TCGLabel *lfail;
> +    TCGv EA;
> +    TCGv cr0;
> +    TCGv t0;
> +    int rs = rS(ctx->opcode);
>   
> +    lfail = gen_new_label();
> +    EA = tcg_temp_new();
> +    cr0 = tcg_temp_new();
> +    t0 = tcg_temp_new();
> +
> +    tcg_gen_mov_tl(cr0, cpu_so);
>       gen_set_access_type(ctx, ACCESS_RES);
> -    gen_addr_reg_index(ctx, t0);
> -    tcg_gen_brcond_tl(TCG_COND_NE, t0, cpu_reserve, l1);
> -    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_size, memop_size(memop), l1);
> +    gen_addr_reg_index(ctx, EA);
> +    tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, lfail);
> +    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_size, memop_size(memop), lfail);
>   
> -    t0 = tcg_temp_new();
>       tcg_gen_atomic_cmpxchg_tl(t0, cpu_reserve, cpu_reserve_val,
> -                              cpu_gpr[reg], ctx->mem_idx,
> -                              DEF_MEMOP(memop) | MO_ALIGN);
> +                              cpu_gpr[rs], ctx->mem_idx,
> +                              memop | MO_ALIGN);

Lost DEF_MEMOP here.  Otherwise,

Reviewed-by: Richard Henderson <[e-mail]>

r~

Patch

diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 77e1c5abb6..cf99e961f7 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -3812,31 +3812,32 @@  static void gen_stdat(DisasContext *ctx)
 
 static void gen_conditional_store(DisasContext *ctx, MemOp memop)
 {
-    TCGLabel *l1 = gen_new_label();
-    TCGLabel *l2 = gen_new_label();
-    TCGv t0 = tcg_temp_new();
-    int reg = rS(ctx->opcode);
+    TCGLabel *lfail;
+    TCGv EA;
+    TCGv cr0;
+    TCGv t0;
+    int rs = rS(ctx->opcode);
 
+    lfail = gen_new_label();
+    EA = tcg_temp_new();
+    cr0 = tcg_temp_new();
+    t0 = tcg_temp_new();
+
+    tcg_gen_mov_tl(cr0, cpu_so);
     gen_set_access_type(ctx, ACCESS_RES);
-    gen_addr_reg_index(ctx, t0);
-    tcg_gen_brcond_tl(TCG_COND_NE, t0, cpu_reserve, l1);
-    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_size, memop_size(memop), l1);
+    gen_addr_reg_index(ctx, EA);
+    tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, lfail);
+    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_size, memop_size(memop), lfail);
 
-    t0 = tcg_temp_new();
     tcg_gen_atomic_cmpxchg_tl(t0, cpu_reserve, cpu_reserve_val,
-                              cpu_gpr[reg], ctx->mem_idx,
-                              DEF_MEMOP(memop) | MO_ALIGN);
+                              cpu_gpr[rs], ctx->mem_idx,
+                              memop | MO_ALIGN);
     tcg_gen_setcond_tl(TCG_COND_EQ, t0, t0, cpu_reserve_val);
     tcg_gen_shli_tl(t0, t0, CRF_EQ_BIT);
-    tcg_gen_or_tl(t0, t0, cpu_so);
-    tcg_gen_trunc_tl_i32(cpu_crf[0], t0);
-    tcg_gen_br(l2);
+    tcg_gen_or_tl(cr0, cr0, t0);
 
-    gen_set_label(l1);
-
-    tcg_gen_trunc_tl_i32(cpu_crf[0], cpu_so);
-
-    gen_set_label(l2);
+    gen_set_label(lfail);
+    tcg_gen_trunc_tl_i32(cpu_crf[0], cr0);
     tcg_gen_movi_tl(cpu_reserve, -1);
 }
 
@@ -3890,25 +3891,26 @@  static void gen_lqarx(DisasContext *ctx)
 /* stqcx. */
 static void gen_stqcx_(DisasContext *ctx)
 {
-    TCGLabel *lab_fail, *lab_over;
-    int rs = rS(ctx->opcode);
+    TCGLabel *lfail;
     TCGv EA, t0, t1;
+    TCGv cr0;
     TCGv_i128 cmp, val;
+    int rs = rS(ctx->opcode);
 
     if (unlikely(rs & 1)) {
         gen_inval_exception(ctx, POWERPC_EXCP_INVAL_INVAL);
         return;
     }
 
-    lab_fail = gen_new_label();
-    lab_over = gen_new_label();
+    lfail = gen_new_label();
+    EA = tcg_temp_new();
+    cr0 = tcg_temp_new();
 
+    tcg_gen_mov_tl(cr0, cpu_so);
     gen_set_access_type(ctx, ACCESS_RES);
-    EA = tcg_temp_new();
     gen_addr_reg_index(ctx, EA);
-
-    tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, lab_fail);
-    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_size, 128, lab_fail);
+    tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, lfail);
+    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_size, 128, lfail);
 
     cmp = tcg_temp_new_i128();
     val = tcg_temp_new_i128();
@@ -3931,15 +3933,10 @@  static void gen_stqcx_(DisasContext *ctx)
 
     tcg_gen_setcondi_tl(TCG_COND_EQ, t0, t0, 0);
     tcg_gen_shli_tl(t0, t0, CRF_EQ_BIT);
-    tcg_gen_or_tl(t0, t0, cpu_so);
-    tcg_gen_trunc_tl_i32(cpu_crf[0], t0);
-
-    tcg_gen_br(lab_over);
-    gen_set_label(lab_fail);
-
-    tcg_gen_trunc_tl_i32(cpu_crf[0], cpu_so);
+    tcg_gen_or_tl(cr0, cr0, t0);
 
-    gen_set_label(lab_over);
+    gen_set_label(lfail);
+    tcg_gen_trunc_tl_i32(cpu_crf[0], cr0);
     tcg_gen_movi_tl(cpu_reserve, -1);
 }
 #endif /* defined(TARGET_PPC64) */