MIPS: math-emu: Emulate MIPSr6 sel.fmt instruction

Add support for emulating the MIPSr6 sel.fmt instruction, which was
previously missing from the FPU emulation code. This instruction selects
its result from 2 possible source registers, based upon bit 0 of the
destination register, and is valid only for S (single) & D (double) data
types.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Maciej W. Rozycki <macro@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13153/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/math-emu/cp1emu.c

@@ -1675,7 +1675,7 @@ static int fpu_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 			union ieee754sp(*b) (union ieee754sp, union ieee754sp);
 			union ieee754sp(*u) (union ieee754sp);
 		} handler;
-		union ieee754sp fs, ft;
+		union ieee754sp fd, fs, ft;
 
 		switch (MIPSInst_FUNC(ir)) {
 			/* binary ops */
@@ -1946,6 +1946,17 @@ static int fpu_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 			rfmt = w_fmt;
 			goto copcsr;
 
+		case fsel_op:
+			if (!cpu_has_mips_r6)
+				return SIGILL;
+
+			SPFROMREG(fd, MIPSInst_FD(ir));
+			if (fd.bits & 0x1)
+				SPFROMREG(rv.s, MIPSInst_FT(ir));
+			else
+				SPFROMREG(rv.s, MIPSInst_FS(ir));
+			break;
+
 		case fcvtl_op:
 			if (!cpu_has_mips_3_4_5_64_r2_r6)
 				return SIGILL;
@@ -1994,7 +2005,7 @@ static int fpu_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 	}
 
 	case d_fmt: {
-		union ieee754dp fs, ft;
+		union ieee754dp fd, fs, ft;
 		union {
 			union ieee754dp(*b) (union ieee754dp, union ieee754dp);
 			union ieee754dp(*u) (union ieee754dp);
@@ -2244,6 +2255,17 @@ static int fpu_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 			rfmt = w_fmt;
 			goto copcsr;
 
+		case fsel_op:
+			if (!cpu_has_mips_r6)
+				return SIGILL;
+
+			DPFROMREG(fd, MIPSInst_FD(ir));
+			if (fd.bits & 0x1)
+				DPFROMREG(rv.d, MIPSInst_FT(ir));
+			else
+				DPFROMREG(rv.d, MIPSInst_FS(ir));
+			break;
+
 		case fcvtl_op:
 			if (!cpu_has_mips_3_4_5_64_r2_r6)
 				return SIGILL;