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>

disas/ppc.c

@@ -1765,6 +1765,9 @@ extract_tbr (unsigned long insn,
 /* An X_MASK with the RA and RB fields fixed.  */
 #define XRARB_MASK (X_MASK | RA_MASK | RB_MASK)
 
+/* An X form instruction with the RA field fixed.  */
+#define XRA(op, xop, ra) (X((op), (xop)) | (((ra) << 16) & XRA_MASK))
+
 /* An XRARB_MASK, but with the L bit clear.  */
 #define XRLARB_MASK (XRARB_MASK & ~((unsigned long) 1 << 16))
 
@@ -4998,6 +5001,8 @@ const struct powerpc_opcode powerpc_opcodes[] = {
 { "ddivq",   XRC(63,546,0), X_MASK,	POWER6,		{ FRT, FRA, FRB } },
 { "ddivq.",  XRC(63,546,1), X_MASK,	POWER6,		{ FRT, FRA, FRB } },
 
+{ "mffsl",   XRA(63,583,12), XRARB_MASK,	POWER9,	{ FRT } },
+
 { "mffs",    XRC(63,583,0), XRARB_MASK,	COM,		{ FRT } },
 { "mffs.",   XRC(63,583,1), XRARB_MASK,	COM,		{ FRT } },
 

target/ppc/cpu.h

@@ -591,7 +591,7 @@ enum {
 #define FPSCR_XE     3  /* Floating-point inexact exception enable           */
 #define FPSCR_NI     2  /* Floating-point non-IEEE mode                      */
 #define FPSCR_RN1    1
-#define FPSCR_RN     0  /* Floating-point rounding control                   */
+#define FPSCR_RN0    0  /* Floating-point rounding control                   */
 #define fpscr_fex    (((env->fpscr) >> FPSCR_FEX)    & 0x1)
 #define fpscr_vx     (((env->fpscr) >> FPSCR_VX)     & 0x1)
 #define fpscr_ox     (((env->fpscr) >> FPSCR_OX)     & 0x1)
@@ -614,7 +614,7 @@ enum {
 #define fpscr_ze     (((env->fpscr) >> FPSCR_ZE)     & 0x1)
 #define fpscr_xe     (((env->fpscr) >> FPSCR_XE)     & 0x1)
 #define fpscr_ni     (((env->fpscr) >> FPSCR_NI)     & 0x1)
-#define fpscr_rn     (((env->fpscr) >> FPSCR_RN)     & 0x3)
+#define fpscr_rn     (((env->fpscr) >> FPSCR_RN0)    & 0x3)
 /* Invalid operation exception summary */
 #define fpscr_ix ((env->fpscr) & ((1 << FPSCR_VXSNAN) | (1 << FPSCR_VXISI)  | \
                                   (1 << FPSCR_VXIDI)  | (1 << FPSCR_VXZDZ)  | \
@@ -640,15 +640,15 @@ enum {
 #define FP_VXZDZ        (1ull << FPSCR_VXZDZ)
 #define FP_VXIMZ        (1ull << FPSCR_VXIMZ)
 #define FP_VXVC         (1ull << FPSCR_VXVC)
-#define FP_FR           (1ull << FSPCR_FR)
+#define FP_FR           (1ull << FPSCR_FR)
 #define FP_FI           (1ull << FPSCR_FI)
 #define FP_C            (1ull << FPSCR_C)
 #define FP_FL           (1ull << FPSCR_FL)
 #define FP_FG           (1ull << FPSCR_FG)
 #define FP_FE           (1ull << FPSCR_FE)
 #define FP_FU           (1ull << FPSCR_FU)
 #define FP_FPCC         (FP_FL | FP_FG | FP_FE | FP_FU)
-#define FP_FPRF         (FP_C  | FP_FL | FP_FG | FP_FE | FP_FU)
+#define FP_FPRF         (FP_C | FP_FPCC)
 #define FP_VXSOFT       (1ull << FPSCR_VXSOFT)
 #define FP_VXSQRT       (1ull << FPSCR_VXSQRT)
 #define FP_VXCVI        (1ull << FPSCR_VXCVI)
@@ -659,7 +659,12 @@ enum {
 #define FP_XE           (1ull << FPSCR_XE)
 #define FP_NI           (1ull << FPSCR_NI)
 #define FP_RN1          (1ull << FPSCR_RN1)
-#define FP_RN           (1ull << FPSCR_RN)
+#define FP_RN0          (1ull << FPSCR_RN0)
+#define FP_RN           (FP_RN1 | FP_RN0)
+
+#define FP_MODE         FP_RN
+#define FP_ENABLES      (FP_VE | FP_OE | FP_UE | FP_ZE | FP_XE)
+#define FP_STATUS       (FP_FR | FP_FI | FP_FPRF)
 
 /* the exception bits which can be cleared by mcrfs - includes FX */
 #define FP_EX_CLEAR_BITS (FP_FX     | FP_OX     | FP_UX     | FP_ZX     | \

target/ppc/fpu_helper.c

@@ -403,7 +403,7 @@ void helper_fpscr_clrbit(CPUPPCState *env, uint32_t bit)
     if (prev == 1) {
         switch (bit) {
         case FPSCR_RN1:
-        case FPSCR_RN:
+        case FPSCR_RN0:
             fpscr_set_rounding_mode(env);
             break;
         case FPSCR_VXSNAN:
@@ -557,7 +557,7 @@ void helper_fpscr_setbit(CPUPPCState *env, uint32_t bit)
             }
             break;
         case FPSCR_RN1:
-        case FPSCR_RN:
+        case FPSCR_RN0:
             fpscr_set_rounding_mode(env);
             break;
         default:

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)
 {

target/ppc/translate/fp-ops.inc.c

@@ -104,7 +104,9 @@ GEN_HANDLER_E(fcpsgn, 0x3F, 0x08, 0x00, 0x00000000, PPC_NONE, PPC2_ISA205),
 GEN_HANDLER_E(fmrgew, 0x3F, 0x06, 0x1E, 0x00000001, PPC_NONE, PPC2_VSX207),
 GEN_HANDLER_E(fmrgow, 0x3F, 0x06, 0x1A, 0x00000001, PPC_NONE, PPC2_VSX207),
 GEN_HANDLER(mcrfs, 0x3F, 0x00, 0x02, 0x0063F801, PPC_FLOAT),
-GEN_HANDLER(mffs, 0x3F, 0x07, 0x12, 0x001FF800, PPC_FLOAT),
+GEN_HANDLER_E_2(mffs, 0x3F, 0x07, 0x12, 0x00, 0x00000000, PPC_FLOAT, PPC_NONE),
+GEN_HANDLER_E_2(mffsl, 0x3F, 0x07, 0x12, 0x18, 0x00000000, PPC_FLOAT,
+    PPC2_ISA300),
 GEN_HANDLER(mtfsb0, 0x3F, 0x06, 0x02, 0x001FF800, PPC_FLOAT),
 GEN_HANDLER(mtfsb1, 0x3F, 0x06, 0x01, 0x001FF800, PPC_FLOAT),
 GEN_HANDLER(mtfsf, 0x3F, 0x07, 0x16, 0x00000000, PPC_FLOAT),