MIPS: math-emu: Add mfhc1 & mthc1 support.

This patch adds support for the mfhc1 & mthc1 instructions to the FPU
emulator. These instructions were introduced in release 2 of the MIPS32
& MIPS64 architectures and allow access to the most significant 32 bits
of a 64-bit FP register.

[ralf@linux-mips.org: Fix ifdef hell added by original patch.]
Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6112/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/uapi/asm/inst.h

@@ -98,8 +98,9 @@ enum rt_op {
  */
 enum cop_op {
 	mfc_op	      = 0x00, dmfc_op	    = 0x01,
-	cfc_op	      = 0x02, mtc_op	    = 0x04,
-	dmtc_op	      = 0x05, ctc_op	    = 0x06,
+	cfc_op	      = 0x02, mfhc_op	    = 0x03,
+	mtc_op        = 0x04, dmtc_op	    = 0x05,
+	ctc_op	      = 0x06, mthc_op	    = 0x07,
 	bc_op	      = 0x08, cop_op	    = 0x10,
 	copm_op	      = 0x18
 };

arch/mips/math-emu/cp1emu.c

@@ -878,6 +878,10 @@ static inline int cop1_64bit(struct pt_regs *xcp)
 			ctx->fpr[x & ~1] >> 32 << 32 | (u32)(si) : \
 			ctx->fpr[x & ~1] << 32 >> 32 | (u64)(si) << 32)
 
+#define SIFROMHREG(si, x)	((si) = (int)(ctx->fpr[x] >> 32))
+#define SITOHREG(si, x)		(ctx->fpr[x] = \
+				ctx->fpr[x] << 32 >> 32 | (u64)(si) << 32)
+
 #define DIFROMREG(di, x) ((di) = ctx->fpr[x & ~(cop1_64bit(xcp) == 0)])
 #define DITOREG(di, x)	(ctx->fpr[x & ~(cop1_64bit(xcp) == 0)] = (di))
 
@@ -1055,6 +1059,25 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 			break;
 #endif
 
+		case mfhc_op:
+			if (!cpu_has_mips_r2)
+				goto sigill;
+
+			/* copregister rd -> gpr[rt] */
+			if (MIPSInst_RT(ir) != 0) {
+				SIFROMHREG(xcp->regs[MIPSInst_RT(ir)],
+					MIPSInst_RD(ir));
+			}
+			break;
+
+		case mthc_op:
+			if (!cpu_has_mips_r2)
+				goto sigill;
+
+			/* copregister rd <- gpr[rt] */
+			SITOHREG(xcp->regs[MIPSInst_RT(ir)], MIPSInst_RD(ir));
+			break;
+
 		case mfc_op:
 			/* copregister rd -> gpr[rt] */
 			if (MIPSInst_RT(ir) != 0) {
@@ -1263,6 +1286,7 @@ static int cop1Emulate(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 #endif
 
 	default:
+sigill:
 		return SIGILL;
 	}