mips: allow disabling CP1 emulator

This saves RAM, obviously.

arch/mips/Kconfig

@@ -2216,6 +2216,16 @@ config MIPS_FP_SUPPORT
 
 	  If unsure, say y.
 
+config MIPS_FP_DISABLE_EMULATOR
+	bool "Disable FPU emulator"
+	depends on MIPS_FP_SUPPORT
+	default n
+	help
+	  If you know that your processor supports all floating point instructions
+	  then you can say y here to shrink the kernel a little (~40KiB on MIPS32).
+
+	  Don't enable this unless you absolutely know what you're doing.
+
 config CPU_R2300_FPU
 	bool
 	depends on MIPS_FP_SUPPORT

arch/mips/math-emu/cp1emu.c

@@ -1465,6 +1465,10 @@ static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 {
 	unsigned int rcsr = 0;	/* resulting csr */
 
+#ifdef CONFIG_MIPS_FP_DISABLE_EMULATOR
+	return 0;
+#endif
+
 	MIPS_FPU_EMU_INC_STATS(cp1xops);
 
 	switch (MIPSInst_FMA_FFMT(ir)) {
@@ -1695,6 +1699,10 @@ static int fpu_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 	} rv;			/* resulting value */
 	u64 bits;
 
+#ifdef CONFIG_MIPS_FP_DISABLE_EMULATOR
+	return 0;
+#endif
+
 	MIPS_FPU_EMU_INC_STATS(cp1ops);
 	switch (rfmt = (MIPSInst_FFMT(ir) & 0xf)) {
 	case s_fmt: {		/* 0 */