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imx8: move fpon()/fpoff() into l.s

avoid the dynamic code generating syswr() in the hot path...

--- a/sys/src/9/imx8/fns.h

+++ b/sys/src/9/imx8/fns.h

@@ -14,6 +14,8 @@

 extern void forkret(void);

 extern void noteret(void);

 extern void returnto(void*);

+extern void fpon(void);

+extern void fpoff(void);

 extern void fpsaveregs(void*);

 extern void fploadregs(void*);

 extern void smccall(Ureg*);

--- a/sys/src/9/imx8/fpu.c

+++ b/sys/src/9/imx8/fpu.c

@@ -20,18 +20,6 @@

 }

 void

-fpon(void)

-{

-	syswr(CPACR_EL1, 3<<20);

-}

-

-void

-fpoff(void)

-{

-	syswr(CPACR_EL1, 0<<20);

-}

-

-void

 fpinit(void)

 {

 	fpon();

--- a/sys/src/9/imx8/l.s

+++ b/sys/src/9/imx8/l.s

@@ -394,6 +394,19 @@

 	ISB	$SY

 	RETURN

+/*

+ * floating-point support.

+ */

+TEXT fpon(SB), 1, $-4

+	MOVW $(3<<20), R0

+	MSR R0, CPACR_EL1

+	RETURN

+

+TEXT fpoff(SB), 1, $-4

+	MOVW $(0<<20), R0

+	MSR R0, CPACR_EL1

+	RETURN

+

 TEXT fpsaveregs(SB), 1, $-4

 	WORD	$(1<<30 | 3 << 26 | 2<<22 | 0x1F<<16 | 3<<10 | 0<<5 | 0)  /* MOV { V0, V1, V2, V3  }, (R0)64! */

 	WORD	$(1<<30 | 3 << 26 | 2<<22 | 0x1F<<16 | 3<<10 | 0<<5 | 4)  /* MOV { V4, V5, V6, V7  }, (R0)64! */