[PATCH v2 4/4] target/ppc: Rework store conditional to avoid branch

[Nicholas Piggin]

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_.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
v2:
- Reinstate lost DEF_MEMOP [Richard]

I think the DEF_MEMOP is redundant here, but admit that's not something
that should be changed with this patch. I will look at cleaning those up
later.

Thanks,
Nick

 target/ppc/translate.c | 63 ++++++++++++++++++++----------------------
 1 file changed, 30 insertions(+), 33 deletions(-)

diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index acb99d8691..434caad258 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -3813,31 +3813,32 @@ 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_length, 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_length, 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,
+                              cpu_gpr[rs], ctx->mem_idx,
                               DEF_MEMOP(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);
 }
 
@@ -3891,25 +3892,26 @@ 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_length, 16, lab_fail);
+    tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, lfail);
+    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_length, 16, lfail);
 
     cmp = tcg_temp_new_i128();
     val = tcg_temp_new_i128();
@@ -3932,15 +3934,10 @@ 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) */
-- 
2.40.1