[Qemu-devel] [PATCH v2] target-sh4: add atomic tas

[Laurent Vivier <laurent@vivier.eu>]

Implement real atomic tas:

    When (Rn) = 0, 1 -> T
    Otherwise, 0 -> T
    In both cases, 1 -> MSB of (Rn)

using atomic_fetch_or_i32() and setcondi_i32().

Tested with image from:
http://wiki.qemu.org/download/sh-test-0.2.tar.bz2

This image contains a "tas_test" that runs without
error with this change.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
v2:
- don't use helper but atomic_fetch_or_i32
  Thank you Paolo!

 target-sh4/translate.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/target-sh4/translate.c b/target-sh4/translate.c
index c89a147..1b83d59 100644
--- a/target-sh4/translate.c
+++ b/target-sh4/translate.c
@@ -1640,18 +1640,15 @@ static void _decode_opc(DisasContext * ctx)
 	tcg_gen_shri_i32(REG(B11_8), REG(B11_8), 16);
 	return;
     case 0x401b:		/* tas.b @Rn */
-	{
-	    TCGv addr, val;
-	    addr = tcg_temp_local_new();
-	    tcg_gen_mov_i32(addr, REG(B11_8));
-	    val = tcg_temp_local_new();
-            tcg_gen_qemu_ld_i32(val, addr, ctx->memidx, MO_UB);
+        {
+            TCGv val = tcg_temp_new();
+            TCGv msb = tcg_const_i32(0x80);
+            tcg_gen_atomic_fetch_or_i32(val, REG(B11_8), msb,
+                                        ctx->memidx, MO_UB);
+            tcg_temp_free(msb);
             tcg_gen_setcondi_i32(TCG_COND_EQ, cpu_sr_t, val, 0);
-	    tcg_gen_ori_i32(val, val, 0x80);
-            tcg_gen_qemu_st_i32(val, addr, ctx->memidx, MO_UB);
-	    tcg_temp_free(val);
-	    tcg_temp_free(addr);
-	}
+            tcg_temp_free(val);
+        }
 	return;
     case 0xf00d: /* fsts FPUL,FRn - FPSCR: Nothing */
 	CHECK_FPU_ENABLED
-- 
2.7.4