cmd/internal/obj/mips, cmd/internal/obj: reduce MIPS register space

Change-Id: I43458ce0e78ffc3d0943d28dc8df8e1c9e4cf679
Reviewed-on: https://go-review.googlesource.com/18821Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/internal/obj/mips/a.out.go

@@ -114,7 +114,7 @@ const (
 	REG_LO
 
 	// co-processor 0 control registers
-	REG_M0 = obj.RBaseMIPS64 + 1024 + iota
+	REG_M0
 	REG_M1
 	REG_M2
 	REG_M3
@@ -148,7 +148,7 @@ const (
 	REG_M31
 
 	// FPU control registers
-	REG_FCR0 = obj.RBaseMIPS64 + 2048 + iota
+	REG_FCR0
 	REG_FCR1
 	REG_FCR2
 	REG_FCR3
@@ -181,6 +181,8 @@ const (
 	REG_FCR30
 	REG_FCR31
 
+	REG_LAST = REG_FCR31 // the last defined register
+
 	REG_SPECIAL = REG_M0
 
 	REGZERO  = REG_R0 /* set to zero */

src/cmd/internal/obj/mips/list0.go

@@ -35,7 +35,7 @@ import (
 )
 
 func init() {
-	obj.RegisterRegister(obj.RBaseMIPS64, REG_FCR0+1024, Rconv)
+	obj.RegisterRegister(obj.RBaseMIPS64, REG_LAST&^1023+1024, Rconv)
 	obj.RegisterOpcode(obj.ABaseMIPS64, Anames)
 }
 

src/cmd/internal/obj/util.go

@@ -529,7 +529,7 @@ const (
 	RBaseARM    = 3 * 1024
 	RBasePPC64  = 4 * 1024  // range [4k, 8k)
 	RBaseARM64  = 8 * 1024  // range [8k, 13k)
-	RBaseMIPS64 = 13 * 1024 // range [13k, 16k)
+	RBaseMIPS64 = 13 * 1024 // range [13k, 14k)
 )
 
 // RegisterRegister binds a pretty-printer (Rconv) for register