ppc: Add support for 'mffsl' instruction

ISA 3.0B added a set of Floating-Point Status and Control Register (FPSCR)
instructions: mffsce, mffscdrn, mffscdrni, mffscrn, mffscrni, mffsl.
This patch adds support for 'mffsl'.

'mffsl' is identical to 'mffs', except it only returns mode, status, and enable
bits from the FPSCR.

On CPUs without support for 'mffsl' (below ISA 3.0), the 'mffsl' instruction
will execute identically to 'mffs'.

Note: I renamed FPSCR_RN to FPSCR_RN0 so I could create an FPSCR_RN mask which
is both bits of the FPSCR rounding mode, as defined in the ISA.

I also fixed a typo in the definition of FPSCR_FR.

Signed-off-by: Paul A. Clarke <pc@us.ibm.com>

v4:
- nit: added some braces to resolve a checkpatch complaint.

v3:
- Changed tcg_gen_and_i64 to tcg_gen_andi_i64, eliminating the need for a
  temporary, per review from Richard Henderson.

v2:
- I found that I copied too much of the 'mffs' implementation.
  The 'Rc' condition code bits are not needed for 'mffsl'.  Removed.
- I now free the (renamed) 'tmask' temporary.
- I now bail early for older ISA to the original 'mffs' implementation.

Message-Id: <1565982203-11048-1-git-send-email-pc@us.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 22 insertions, 0 deletions

diff --git a/target/ppc/translate/fp-impl.inc.c b/target/ppc/translate/fp-impl.inc.c
index 9dcff947c0..7cd9d8db05 100644
--- a/target/ppc/translate/fp-impl.inc.c
+++ b/target/ppc/translate/fp-impl.inc.c
@@ -617,6 +617,28 @@ static void gen_mffs(DisasContext *ctx)
     tcg_temp_free_i64(t0);
 }
 
+/* mffsl */
+static void gen_mffsl(DisasContext *ctx)
+{
+    TCGv_i64 t0;
+
+    if (unlikely(!(ctx->insns_flags2 & PPC2_ISA300))) {
+        return gen_mffs(ctx);
+    }
+
+    if (unlikely(!ctx->fpu_enabled)) {
+        gen_exception(ctx, POWERPC_EXCP_FPU);
+        return;
+    }
+    t0 = tcg_temp_new_i64();
+    gen_reset_fpstatus();
+    tcg_gen_extu_tl_i64(t0, cpu_fpscr);
+    /* Mask everything except mode, status, and enables.  */
+    tcg_gen_andi_i64(t0, t0, FP_MODE | FP_STATUS | FP_ENABLES);
+    set_fpr(rD(ctx->opcode), t0);
+    tcg_temp_free_i64(t0);
+}
+
 /* mtfsb0 */
 static void gen_mtfsb0(DisasContext *ctx)
 {