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Re: [Qemu-ppc] [PATCH v1 07/10] target/ppc: update ov/ov32 for nego


From: Richard Henderson
Subject: Re: [Qemu-ppc] [PATCH v1 07/10] target/ppc: update ov/ov32 for nego
Date: Tue, 21 Feb 2017 06:55:46 +1100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0

On 02/20/2017 09:11 PM, Nikunj A Dadhania wrote:
For 64-bit mode if the register RA contains 0x8000_0000_0000_0000, OV
and OV32 are set to 1.

For 32-bit mode if the register RA contains 0x8000_0000, OV and OV32 are
set to 1.

Use the tcg-ops for negation (neg_tl) and drop gen_op_arith_neg() as
nego was the last user.

Signed-off-by: Nikunj A Dadhania <address@hidden>
---
 target/ppc/translate.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 9fa3b5a..0168e1c 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -1473,14 +1473,6 @@ static void gen_subfic(DisasContext *ctx)
 }

 /* neg neg. nego nego. */
-static inline void gen_op_arith_neg(DisasContext *ctx, bool compute_ov)
-{
-    TCGv zero = tcg_const_tl(0);
-    gen_op_arith_subf(ctx, cpu_gpr[rD(ctx->opcode)], cpu_gpr[rA(ctx->opcode)],
-                      zero, 0, 0, compute_ov, Rc(ctx->opcode));
-    tcg_temp_free(zero);
-}
-
 static void gen_neg(DisasContext *ctx)
 {
     tcg_gen_neg_tl(cpu_gpr[rD(ctx->opcode)], cpu_gpr[rA(ctx->opcode)]);
@@ -1488,7 +1480,20 @@ static void gen_neg(DisasContext *ctx)

 static void gen_nego(DisasContext *ctx)
 {
-    gen_op_arith_neg(ctx, 1);
+    TCGv t0 = tcg_temp_new();
+    TCGv zero = tcg_const_tl(0);
+
+    if (NARROW_MODE(ctx)) {
+        tcg_gen_xori_tl(t0, cpu_gpr[rA(ctx->opcode)], INT32_MIN);
+    } else {
+        tcg_gen_xori_tl(t0, cpu_gpr[rA(ctx->opcode)], (target_ulong)INT64_MIN);
+    }
+
+    tcg_gen_setcond_tl(TCG_COND_EQ, cpu_ov, t0, zero);
+    tcg_gen_mov_tl(cpu_ov32, cpu_ov);
+    tcg_gen_neg_tl(cpu_gpr[rD(ctx->opcode)], cpu_gpr[rA(ctx->opcode)]);
+    tcg_temp_free(t0);
+    tcg_temp_free(zero);
 }

Again, you're forgetting "nego.". Don't try to simplify from gen_op_arith_subf by hand.


r~



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