patch-2.4.0-test10 linux/arch/i386/kernel/i387.c

• Lines: 75
• Date: Mon Oct 23 15:57:29 2000
• Orig file: v2.4.0-test9/linux/arch/i386/kernel/i387.c
• Orig date: Sun Sep 3 10:57:33 2000

diff -u --recursive --new-file v2.4.0-test9/linux/arch/i386/kernel/i387.c linux/arch/i386/kernel/i387.c
@@ -33,22 +33,24 @@
 #endif
 
 /*
- * FPU lazy state save handling.
+ * The _current_ task is using the FPU for the first time
+ * so initialize it and set the mxcsr to its default
+ * value at reset if we support FXSR and then
+ * remeber the current task has used the FPU.
  */
-
-void save_fpu( struct task_struct *tsk )
+void init_fpu(void)
 {
-	if ( HAVE_FXSR ) {
-		asm volatile( "fxsave %0 ; fwait"
-			      : "=m" (tsk->thread.i387.fxsave) );
-	} else {
-		asm volatile( "fnsave %0 ; fwait"
-			      : "=m" (tsk->thread.i387.fsave) );
-	}
-	tsk->flags &= ~PF_USEDFPU;
-	stts();
+	__asm__("fninit");
+	if ( HAVE_FXSR )
+		load_mxcsr(0x1f80);
+		
+	current->used_math = 1;
 }
 
+/*
+ * FPU lazy state save handling.
+ */
+
 void save_init_fpu( struct task_struct *tsk )
 {
 	if ( HAVE_FXSR ) {
@@ -79,16 +81,16 @@
 
 static inline unsigned short twd_i387_to_fxsr( unsigned short twd )
 {
-	unsigned short ret = 0;
-	int i;
-
-	for ( i = 0 ; i < 8 ; i++ ) {
-		if ( (twd & 0x3) != 0x3 ) {
-			ret |= (1 << i);
-		}
-		twd = twd >> 2;
-	}
-	return ret;
+	unsigned int tmp; /* to avoid 16 bit prefixes in the code */
+ 
+	/* Transform each pair of bits into 01 (valid) or 00 (empty) */
+        tmp = ~twd;
+        tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
+        /* and move the valid bits to the lower byte. */
+        tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
+        tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
+        tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
+        return tmp;
 }
 
 static inline unsigned long twd_fxsr_to_i387( struct i387_fxsave_struct *fxsave )
@@ -105,8 +107,8 @@
 		if ( twd & 0x1 ) {
 			st = (struct _fpxreg *) FPREG_ADDR( fxsave, i );
 
-			switch ( st->exponent ) {
-			case 0xffff:
+			switch ( st->exponent & 0x7fff ) {
+			case 0x7fff:
 				tag = 2;		/* Special */
 				break;
 			case 0x0000: