[linuxsh-dev] FPU patch update

[NIIBE Y. <gn...@m1...>]

Here is an update of FPU patch, which includes fcnvsd exception fix
by Kaz.  Please note that we need new GCC to build the kernel with
this patch.
	ftp://ftp.m17n.org/pub/linux-sh/testing/gcc-sh-linux_3.0.3-2.diff.gz

For me, it works fine with the case of GNU Java.

2001-12-28  NIIBE Yutaka  <gn...@m1...>

	(do_fpu_error): Handle denormalized floating point number.
	Remove un-needed grab_fpu.

	* arch/sh/kernel/head.S (_stext): Don't initialize FPU, as FPU is
	not used by kernel.
	(SR): Initial value with FD=1 (no FPU use).

	* include/asm-sh/processor.h (unlazy_fpu): Don't need to grab_fpu.
	(clear_fpu): Call release_fpu.

	* arch/sh/kernel/entry.S (PF_USEDFPU, __PF_USEDFPU): Removed.
	(restore_all, handle_exception): Simplified.
	(__fpu_prepare_fd, __init_task_flags): Removed

	* arch/sh/kernel/fpu.c (enable_fpu_in_danger): Removed.
	(fpu_prepare_fd): Removed.

2001-12-28  Kazumoto Kojima  <kk...@rr...>

	* include/asm-sh/processor.h (FPSCR_ENABLE_MASK, FPSCR_FLAG_MASK):
	New macros.

	* arch/sh/kernel/fpu.c (denormal_to_double, ieee_fpe_handler): 
	New functions.

Index: arch/sh/kernel/entry.S
===================================================================
RCS file: /cvsroot/linuxsh/linux/arch/sh/kernel/entry.S,v
retrieving revision 1.1.1.1
diff -u -3 -p -r1.1.1.1 entry.S
--- arch/sh/kernel/entry.S	2001/10/15 20:44:47	1.1.1.1
+++ arch/sh/kernel/entry.S	2001/12/28 02:48:09
@@ -66,7 +66,6 @@ need_resched	= 20
 tsk_ptrace	= 24
 
 PT_TRACESYS  = 0x00000002
-PF_USEDFPU   = 0x00100000
 
 ENOSYS = 38
 EINVAL = 22
@@ -567,12 +566,6 @@ __irq_stat:
 
 	.align 2
 restore_all:
-#if defined(__SH4__)
-	mov.l	__fpu_prepare_fd, r0
-	jsr	@r0
-	 stc	sr, r4
-#endif
-	!
 	mov.l	@r15+, r0
 	mov.l	@r15+, r1
 	mov.l	@r15+, r2
@@ -585,7 +578,7 @@ restore_all:
 	stc	sr, r8
 	mov.l	__blrb_flags, r9	! BL =1, RB=1
 	or	r9, r8
-	ldc	r8, sr		! here, change the register bank
+	ldc	r8, sr			! here, change the register bank
 	!
 	mov.l	@r15+, r8
 	mov.l	@r15+, r9
@@ -594,25 +587,25 @@ restore_all:
 	mov.l	@r15+, r12
 	mov.l	@r15+, r13
 	mov.l	@r15+, r14
-	mov.l	@r15+, k4	! original stack pointer
+	mov.l	@r15+, k4		! original stack pointer
 	ldc.l	@r15+, spc
 	lds.l	@r15+, pr
-	mov.l	@r15+, k3	! original SR
+	mov.l	@r15+, k3		! original SR
 	ldc.l	@r15+, gbr
 	lds.l	@r15+, mach
 	lds.l	@r15+, macl
-	add	#4, r15	! Skip syscall number
+	add	#4, r15			! Skip syscall number
 	!
 	! Calculate new SR value
-	mov	k3, k2	! original SR value
+	mov	k3, k2			! original SR value
 	mov.l	1f, k1
 	stc	sr, k0
-	and	k1, k0	! Get current FD-bit
+	and	k1, k0			! Get current FD-bit
 	mov.l	2f, k1
-	and	k1, k2	! Mask orignal SR value
-	or	k0, k2	! Inherit current FD-bit
+	and	k1, k2			! Mask orignal SR value
+	or	k0, k2			! Inherit current FD-bit
 	!
-	mov	k3, k0	! Calculate IMASK-bits
+	mov	k3, k0			! Calculate IMASK-bits
 	shlr2	k0
 	and	#0x3c, k0
 	cmp/eq	#0x3c, k0
@@ -620,69 +613,15 @@ restore_all:
 	 shll2	k0
 	mov	g_imask, k0
 	!
-7:	or	k0, k2	! Set the IMASK-bits
+7:	or	k0, k2			! Set the IMASK-bits
 	ldc	k2, ssr
 	!
-#if defined(__SH4__)
-	shll	k2
-	shll	k2
-	bf	9f		! user mode
-	/* Kernel to kernel transition */
-	mov.l	1f, k1
-	tst	k1, k3
-	bf	9f		! it hadn't FPU
-	! Kernel to kernel and FPU was used
-	! There's the case we don't get FPU now
-	stc	sr, k2
-	tst	k1, k2
-	bt	8f
-	! We need to grab FPU here
-	xor	k1, k2
-	ldc	k2, sr		! Grab FPU
-	mov.l	__init_task_flags, k1
-	mov.l	@k1, k2
-	mov.l	__PF_USEDFPU, k0
-	or	k0, k2
-	mov.l	k2, @k1		! Set init_task.flags |= PF_USEDFPU
-	!
-	! Restoring FPU...
-	!
-8:	mov.l	3f, k1
-	lds	k1, fpscr
-	fmov.s	@r15+, fr0
-	fmov.s	@r15+, fr1
-	fmov.s	@r15+, fr2
-	fmov.s	@r15+, fr3
-	fmov.s	@r15+, fr4
-	fmov.s	@r15+, fr5
-	fmov.s	@r15+, fr6
-	fmov.s	@r15+, fr7
-	fmov.s	@r15+, fr8
-	fmov.s	@r15+, fr9
-	fmov.s	@r15+, fr10
-	fmov.s	@r15+, fr11
-	fmov.s	@r15+, fr12
-	fmov.s	@r15+, fr13
-	fmov.s	@r15+, fr14
-	fmov.s	@r15+, fr15
-	lds.l	@r15+, fpscr
-	lds.l	@r15+, fpul
-9:
-#endif
 	mov	k4, r15
 	rte
 	 nop
 
 	.align	2
 __blrb_flags:	.long	0x30000000
-#if defined(__SH4__)
-__fpu_prepare_fd:
-	.long	SYMBOL_NAME(fpu_prepare_fd)
-__init_task_flags:
-	.long	SYMBOL_NAME(init_task_union)+4
-__PF_USEDFPU:
-	.long	PF_USEDFPU
-#endif
 1:	.long	0x00008000	! FD
 2:	.long	0xffff7f0f	! ~(IMASK+FD)
 3:	.long	0x00080000	! SZ=0, PR=1
@@ -732,61 +671,21 @@ handle_exception:
 	! Using k0, k1 for scratch registers (r0_bank1, r1_bank),
 	! save all registers onto stack.
 	!
-	stc	ssr, k0	! from kernel space?
-	shll	k0		! Check MD bit (bit30) by shifting it into the T bit
-	shll	k0
-#if defined(__SH4__)
-	bf/s	8f		! it's from user to kernel transition
-	 mov	r15, k0	! save original stack to k0
-	/* It's a kernel to kernel transition. */
-	/* Is the FPU disabled? */
-	mov.l	2f, k1
-	stc	ssr, k0
-	tst	k1, k0
-	mov.l	4f, k1
-	bf/s	9f		! FPU is not enabled, no need to save it
-	 mov	r15, k0	! save original stack to k0
-	! FPU is enabled, save it
-	! /* XXX: Need to save another bank of FPU if all FPU feature is used */
-	! /* Currently it's not the case for GCC (only udivsi3_i4, divsi3_i4) */
-	sts.l	fpul,  @-r15
-	sts.l	fpscr, @-r15
-	mov.l	6f, k1
-	lds	k1, fpscr
-	mov.l	3f, k1
-	fmov.s	fr15, @-r15
-	fmov.s	fr14, @-r15
-	fmov.s	fr13, @-r15
-	fmov.s	fr12, @-r15
-	fmov.s	fr11, @-r15
-	fmov.s	fr10, @-r15
-	fmov.s	fr9, @-r15
-	fmov.s	fr8, @-r15
-	fmov.s	fr7, @-r15
-	fmov.s	fr6, @-r15
-	fmov.s	fr5, @-r15
-	fmov.s	fr4, @-r15
-	fmov.s	fr3, @-r15
-	fmov.s	fr2, @-r15
-	fmov.s	fr1, @-r15
-	bra 9f
-	 fmov.s	fr0, @-r15
-#else
-	mov.l	3f, k1
-	bt/s	9f		! it's a kernel to kernel transition, and skip the FPU save.
-	 mov	r15, k0	! save original stack to k0 anyway
-#endif
-8:	/* User space to kernel */
+	stc	ssr, k0		! Is it from kernel space?
+	shll	k0		! Check MD bit (bit30) by shifting it into...
+	shll	k0		!       ...the T bit
+	bt/s	9f		! It's a kernel to kernel transition.
+	 mov	r15, k0		! save original stack to k0
+	/* User space to kernel */
 	mov	#0x20, k1
-	shll8	k1			! k1 <= 8192 == THREAD_SIZE
+	shll8	k1		! k1 <= 8192 == THREAD_SIZE
 	add	current, k1
 	mov	k1, r15		! change to kernel stack
 	!
-	mov.l	4f, k1			! let kernel release FPU
-9:	! Save the user registers on the stack.
-	! At this point, k1 should have been set to the new SR value
-  	mov	#-1, k4
-	mov.l	k4, @-r15		! syscall_nr (default: -1)
+9:  	mov	#-1, k4
+	mov.l	3f, k1
+	! Save the user registers on the stack.
+	mov.l	k4, @-r15	! syscall_nr (default: -1)
 	!
 	sts.l	macl, @-r15
 	sts.l	mach, @-r15
@@ -806,11 +705,11 @@ handle_exception:
 	mov.l	r9, @-r15
 	mov.l	r8, @-r15
 	!
-	stc	sr, r8	! Back to normal register bank, and
-	or	k1, r8	! Block all interrupts, may release FPU
+	stc	sr, r8		! Back to normal register bank, and
+	or	k1, r8		! Block all interrupts
 	mov.l	5f, k1
-	and	k1, r8	! ...
-	ldc	r8, sr	! ...changed here.
+	and	k1, r8		! ...
+	ldc	r8, sr		! ...changed here.
 	!
 	mov.l	r7, @-r15
 	mov.l	r6, @-r15
@@ -831,9 +730,7 @@ handle_exception:
 	 nop
 	.align	2
 1:	.long	SYMBOL_NAME(exception_handling_table)
-2:	.long	0x00008000	! FD=1
 3:	.long	0x000000f0	! FD=0, IMASK=15
-4:	.long	0x000080f0	! FD=1, IMASK=15
 5:	.long	0xcfffffff	! RB=0, BL=0
 6:	.long	0x00080000	! SZ=0, PR=1
 
Index: arch/sh/kernel/fpu.c
===================================================================
RCS file: /cvsroot/linuxsh/linux/arch/sh/kernel/fpu.c,v
retrieving revision 1.1.1.1
diff -u -3 -p -r1.1.1.1 fpu.c
--- arch/sh/kernel/fpu.c	2001/10/15 20:44:48	1.1.1.1
+++ arch/sh/kernel/fpu.c	2001/12/28 02:48:09
@@ -18,6 +18,10 @@
 #include <asm/processor.h>
 #include <asm/io.h>
 
+/*
+ * Save FPU registers onto task structure.
+ * Assume called with FPU enabled (SR.FD=0).
+ */
 void
 save_fpu(struct task_struct *tsk)
 {
@@ -118,7 +122,8 @@ restore_fpu(struct task_struct *tsk)
  * double precission represents signaling NANS.  
  */
 
-void fpu_init(void)
+static void
+fpu_init(void)
 {
 	asm volatile("lds	%0, fpul\n\t"
 		     "lds	%1, fpscr\n\t"
@@ -160,15 +165,125 @@ void fpu_init(void)
 		     : "r" (0), "r" (FPSCR_INIT));
 }
 
+/**
+ *	denormal_to_double - Given denormalized float number,
+ *	                     store double float
+ *
+ *	@fpu: Pointer to sh_fpu_hard structure
+ *	@n: Index to FP register
+ */
+static void
+denormal_to_double (struct sh_fpu_hard_struct *fpu, int n)
+{
+	unsigned long du, dl;
+	unsigned long x = fpu->fpul;
+	int exp = 1023 - 126;
+
+	if (x != 0 && (x & 0x7f800000) == 0) {
+		du = (x & 0x80000000);
+		while ((x & 0x00800000) == 0) {
+			x <<= 1;
+			exp--;
+		}
+		x &= 0x007fffff;
+		du |= (exp << 20) | (x >> 3);
+		dl = x << 29;
+
+		fpu->fp_regs[n] = du;
+		fpu->fp_regs[n+1] = dl;
+	}
+}
+
+/**
+ *	ieee_fpe_handler - Handle denormalized number exception
+ *
+ *	@regs: Pointer to register structure
+ *
+ *	Returns 1 when it's handled (should not cause exception).
+ */
+static int
+ieee_fpe_handler (struct pt_regs *regs)
+{
+	unsigned short insn = *(unsigned short *) regs->pc;
+	unsigned short finsn;
+	unsigned long nextpc;
+	int nib[4] = {
+		(insn >> 12) & 0xf,
+		(insn >> 8) & 0xf,
+		(insn >> 4) & 0xf,
+		insn & 0xf};
+
+	if (nib[0] == 0xb ||
+	    (nib[0] == 0x4 && nib[2] == 0x0 && nib[3] == 0xb)) /* bsr & jsr */
+		regs->pr = regs->pc + 4;
+  
+	if (nib[0] == 0xa || nib[0] == 0xb) { /* bra & bsr */
+		nextpc = regs->pc + 4 + ((short) ((insn & 0xfff) << 4) >> 3);
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (nib[0] == 0x8 && nib[1] == 0xd) { /* bt/s */
+		if (regs->sr & 1)
+			nextpc = regs->pc + 4 + ((char) (insn & 0xff) << 1);
+		else
+			nextpc = regs->pc + 4;
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (nib[0] == 0x8 && nib[1] == 0xf) { /* bf/s */
+		if (regs->sr & 1)
+			nextpc = regs->pc + 4;
+		else
+			nextpc = regs->pc + 4 + ((char) (insn & 0xff) << 1);
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (nib[0] == 0x4 && nib[3] == 0xb &&
+		 (nib[2] == 0x0 || nib[2] == 0x2)) { /* jmp & jsr */
+		nextpc = regs->regs[nib[1]];
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (nib[0] == 0x0 && nib[3] == 0x3 &&
+		 (nib[2] == 0x0 || nib[2] == 0x2)) { /* braf & bsrf */
+		nextpc = regs->pc + 4 + regs->regs[nib[1]];
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (insn == 0x000b) { /* rts */
+		nextpc = regs->pr;
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else {
+		nextpc = regs->pc + 2;
+		finsn = insn;
+	}
+
+	if ((finsn & 0xf1ff) == 0xf0ad) { /* fcnvsd */
+		struct task_struct *tsk = current;
+
+		save_fpu(tsk);
+		if ((tsk->thread.fpu.hard.fpscr & (1 << 17))) {
+			/* FPU error */
+			denormal_to_double (&tsk->thread.fpu.hard,
+					    (finsn >> 8) & 0xf);
+			tsk->thread.fpu.hard.fpscr &=
+				~(FPSCR_CAUSE_MASK | FPSCR_FLAG_MASK);
+			grab_fpu();
+			restore_fpu(tsk);
+			tsk->flags |= PF_USEDFPU;
+		} else {
+			tsk->thread.trap_no = 11;
+			tsk->thread.error_code = 0;
+			force_sig(SIGFPE, tsk);
+		}
+
+		regs->pc = nextpc;
+		return 1;
+	}
+
+	return 0;
+}
+
 asmlinkage void
 do_fpu_error(unsigned long r4, unsigned long r5, unsigned long r6, unsigned long r7,
 	     struct pt_regs regs)
 {
 	struct task_struct *tsk = current;
 
-	regs.pc += 2;
+	if (ieee_fpe_handler (&regs))
+		return;
 
-	grab_fpu();
+	regs.pc += 2;
 	save_fpu(tsk);
 	tsk->thread.trap_no = 11;
 	tsk->thread.error_code = 0;
@@ -181,102 +296,12 @@ do_fpu_state_restore(unsigned long r4, u
 {
 	struct task_struct *tsk = current;
 
-	if (!user_mode(&regs)) {
-		if (tsk != &init_task) {
-			unlazy_fpu(tsk);
-		}
-		tsk = &init_task;
-		if (tsk->flags & PF_USEDFPU) {
-			/*
-			 * This weird situation can be occurred.
-			 *
-			 * There's race condition in __cli:
-			 *
-			 *   (1) SR --> register
-			 *   (2) Set IMASK of register
-			 *   (3) SR <-- register
-			 *
-			 * Between (1) and (2), or (2) and (3) getting
-			 * interrupt, and interrupt handler (or
-			 * softirq) may use FPU.
-			 *
-			 * Then, SR.FD is overwritten by (3).
-			 *
-			 * This results init_task.PF_USEDFPU is on,
-			 * with SR.FD == 1.
-			 *
-			 */
-			release_fpu();
-			return;
-		}
-	}
-
 	grab_fpu();
-	if (tsk->used_math) {
-		/* Using the FPU again.  */
-		restore_fpu(tsk);
-	} else	{
-		/* First time FPU user.  */
-		fpu_init();
-		tsk->used_math = 1;
-	}
-	tsk->flags |= PF_USEDFPU;
-	release_fpu();
-}
-
-/*
- * Change current FD flag to set FD flag back to exception
- */
-asmlinkage void
-fpu_prepare_fd(unsigned long sr, unsigned long r5, unsigned long r6,
-	       unsigned long r7, struct pt_regs regs)
-{
-	__cli();
 	if (!user_mode(&regs)) {
-		if (init_task.flags & PF_USEDFPU)
-			grab_fpu();
-		else {
-			if (!(sr & SR_FD)) {
-				BUG();
-				release_fpu();
-			}
-		}
+		printk(KERN_ERR "BUG: FPU is used in kernel mode.\n");
 		return;
 	}
 
-	if (sr & SR_FD) { /* Kernel doesn't grab FPU */
-		if (current->flags & PF_USEDFPU)
-			grab_fpu();
-		else {
-			if (init_task.flags & PF_USEDFPU) {
-				/*
-				 * This weird situation can be occurred.
-				 * See the comment in do_fpu_state_restore.
-				 */
-				grab_fpu();
-				save_fpu(&init_task);
-			}
-		}
-	} else {
-		if (init_task.flags & PF_USEDFPU)
-			save_fpu(&init_task);
-		else {
-			BUG();
-			release_fpu();
-		}
-	}
-}
-
-/* Short cut for the FPU exception */
-asmlinkage void
-enable_fpu_in_danger(void)
-{
-	struct task_struct *tsk = current;
-
-	if (tsk != &init_task)
-		unlazy_fpu(tsk);
-
-	tsk = &init_task;
 	if (tsk->used_math) {
 		/* Using the FPU again.  */
 		restore_fpu(tsk);
Index: arch/sh/kernel/head.S
===================================================================
RCS file: /cvsroot/linuxsh/linux/arch/sh/kernel/head.S,v
retrieving revision 1.1.1.1
diff -u -3 -p -r1.1.1.1 head.S
--- arch/sh/kernel/head.S	2001/10/15 20:44:48	1.1.1.1
+++ arch/sh/kernel/head.S	2001/12/28 02:48:09
@@ -50,12 +50,6 @@ ENTRY(_stext)
 	sub	r1, r0		!
 	ldc	r0, r7_bank	! ... and init_task
 	!
-#if defined(__SH4__)
-	!                       Initialize fpu
-	mov.l   7f, r0
-	jsr     @r0
-	 nop
-#endif
 	!			Enable cache
 	mov.l	6f, r0
 	jsr	@r0
@@ -74,12 +68,9 @@ ENTRY(_stext)
 	 nop
 
 	.balign 4
-1:	.long	0x400000F0		! MD=1, RB=0, BL=0, FD=0, IMASK=0xF
+1:	.long	0x400080F0		! MD=1, RB=0, BL=0, FD=1, IMASK=0xF
 2:	.long	SYMBOL_NAME(stack)
 3:	.long	SYMBOL_NAME(__bss_start)
 4:	.long	SYMBOL_NAME(_end)
 5:	.long	SYMBOL_NAME(start_kernel)
 6:	.long	SYMBOL_NAME(cache_init)
-#if defined(__SH4__)
-7:	.long   SYMBOL_NAME(fpu_init)
-#endif
Index: include/asm-sh/processor.h
===================================================================
RCS file: /cvsroot/linuxsh/linux/include/asm-sh/processor.h,v
retrieving revision 1.1.1.1
diff -u -3 -p -r1.1.1.1 processor.h
--- include/asm-sh/processor.h	2001/10/15 20:45:10	1.1.1.1
+++ include/asm-sh/processor.h	2001/12/28 02:48:09
@@ -184,18 +184,22 @@ extern void save_fpu(struct task_struct 
 
 #define unlazy_fpu(tsk) do { 			\
 	if ((tsk)->flags & PF_USEDFPU) {	\
-		grab_fpu();			\
 		save_fpu(tsk); 			\
 	}					\
 } while (0)
 
 #define clear_fpu(tsk) do { 			\
-	if ((tsk)->flags & PF_USEDFPU)	 	\
+	if ((tsk)->flags & PF_USEDFPU) { 	\
 		(tsk)->flags &= ~PF_USEDFPU; 	\
+		release_fpu();			\
+	}					\
 } while (0)
 
 /* Double presision, NANS as NANS, rounding to nearest, no exceptions */
 #define FPSCR_INIT  0x00080000
+
+#define	FPSCR_CAUSE_MASK	0x0001f000	/* Cause bits */
+#define	FPSCR_FLAG_MASK		0x0000007c	/* Flag bits */
 
 /*
  * Return saved PC of a blocked thread.
--