diff --git a/src/cmd/5c/reg.c b/src/cmd/5c/reg.c
index c6d760c509b..42c5193de54 100644
--- a/src/cmd/5c/reg.c
+++ b/src/cmd/5c/reg.c
@@ -1150,12 +1150,13 @@ addreg(Adr *a, int rn)
  *	1	R1
  *	...	...
  *	10	R10
+ *	12  R12
  */
 int32
 RtoB(int r)
 {
 
-	if(r < 2 || r >= REGTMP-2)	// excluded R9 and R10 for m and g
+	if(r < 2 || (r >= REGTMP-2 && r != 12))	// excluded R9 and R10 for m and g, but not R12
 		return 0;
 	return 1L << r;
 }
@@ -1163,7 +1164,7 @@ RtoB(int r)
 int
 BtoR(int32 b)
 {
-	b &= 0x01fcL;	// excluded R9 and R10 for m and g
+	b &= 0x11fcL;	// excluded R9 and R10 for m and g, but not R12
 	if(b == 0)
 		return 0;
 	return bitno(b);
@@ -1174,7 +1175,7 @@ BtoR(int32 b)
  *	18	F2
  *	19	F3
  *	...	...
- *	23	F7
+ *	31	F15
  */
 int32
 FtoB(int f)
@@ -1189,7 +1190,7 @@ int
 BtoF(int32 b)
 {
 
-	b &= 0xfc0000L;
+	b &= 0xfffc0000L;
 	if(b == 0)
 		return 0;
 	return bitno(b) - 16;
diff --git a/src/cmd/5g/reg.c b/src/cmd/5g/reg.c
index 82e2166b847..bc3fca5048a 100644
--- a/src/cmd/5g/reg.c
+++ b/src/cmd/5g/reg.c
@@ -34,8 +34,8 @@
 #include "gg.h"
 #include "opt.h"
 
-#define	NREGVAR	24
-#define	REGBITS	((uint32)0xffffff)
+#define	NREGVAR	32
+#define	REGBITS	((uint32)0xffffffff)
 #define	P2R(p)	(Reg*)(p->reg)
 
 	void	addsplits(void);
@@ -160,6 +160,14 @@ static char* regname[] = {
 	".F5",
 	".F6",
 	".F7",
+	".F8",
+	".F9",
+	".F10",
+	".F11",
+	".F12",
+	".F13",
+	".F14",
+	".F15",
 };
 
 void
@@ -1486,11 +1494,12 @@ addreg(Adr *a, int rn)
  *	1	R1
  *	...	...
  *	10	R10
+ *	12  R12
  */
 int32
 RtoB(int r)
 {
-	if(r >= REGTMP-2)	// excluded R9 and R10 for m and g
+	if(r >= REGTMP-2 && r != 12)	// excluded R9 and R10 for m and g, but not R12
 		return 0;
 	return 1L << r;
 }
@@ -1498,7 +1507,7 @@ RtoB(int r)
 int
 BtoR(int32 b)
 {
-	b &= 0x01fcL;	// excluded R9 and R10 for m and g
+	b &= 0x11fcL;	// excluded R9 and R10 for m and g, but not R12
 	if(b == 0)
 		return 0;
 	return bitno(b);
@@ -1509,7 +1518,7 @@ BtoR(int32 b)
  *	18	F2
  *	19	F3
  *	...	...
- *	23	F7
+ *	31	F15
  */
 int32
 FtoB(int f)
@@ -1524,7 +1533,7 @@ int
 BtoF(int32 b)
 {
 
-	b &= 0xfc0000L;
+	b &= 0xfffc0000L;
 	if(b == 0)
 		return 0;
 	return bitno(b) - 16;
diff --git a/src/cmd/5l/5.out.h b/src/cmd/5l/5.out.h
index 3c726e924b3..56724d3dbce 100644
--- a/src/cmd/5l/5.out.h
+++ b/src/cmd/5l/5.out.h
@@ -49,12 +49,11 @@
 #define REGM        (REGEXT-1)
 /* compiler allocates external registers R10 down */
 #define	REGTMP		11
-#define	REGSB		12
 #define	REGSP		13
 #define	REGLINK		14
 #define	REGPC		15
 
-#define	NFREG		8
+#define	NFREG		16
 #define	FREGRET		0
 #define	FREGEXT		7
 #define	FREGTMP		15