arch/mips/kernel/branch.c - maze/linux - Git at Google

 /*
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
  * Copyright (C) 1996, 97, 2000, 2001 by Ralf Baechle
  * Copyright (C) 2001 MIPS Technologies, Inc.
  */
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/signal.h>
 #include <linux/module.h>
 #include <asm/branch.h>
 #include <asm/cpu.h>
 #include <asm/cpu-features.h>
 #include <asm/fpu.h>
 #include <asm/fpu_emulator.h>
 #include <asm/inst.h>
 #include <asm/ptrace.h>
 #include <asm/uaccess.h>

 /*
  * Calculate and return exception PC in case of branch delay slot
  * for microMIPS and MIPS16e. It does not clear the ISA mode bit.
  */
 int __isa_exception_epc(struct pt_regs *regs)
 {
 	unsigned short inst;
 	long epc = regs->cp0_epc;

 	/* Calculate exception PC in branch delay slot. */
 	if (__get_user(inst, (u16 __user *) msk_isa16_mode(epc))) {
 		/* This should never happen because delay slot was checked. */
 		force_sig(SIGSEGV, current);
 		return epc;
 	}
 	if (cpu_has_mips16) {
 		if (((union mips16e_instruction)inst).ri.opcode
 				== MIPS16e_jal_op)
 			epc += 4;
 		else
 			epc += 2;
 	} else if (mm_insn_16bit(inst))
 		epc += 2;
 	else
 		epc += 4;

 	return epc;
 }

 /*
  * Compute return address and emulate branch in microMIPS mode after an
  * exception only. It does not handle compact branches/jumps and cannot
  * be used in interrupt context. (Compact branches/jumps do not cause
  * exceptions.)
  */
 int __microMIPS_compute_return_epc(struct pt_regs *regs)
 {
 	u16 __user *pc16;
 	u16 halfword;
 	unsigned int word;
 	unsigned long contpc;
 	struct mm_decoded_insn mminsn = { 0 };

 	mminsn.micro_mips_mode = 1;

 	/* This load never faults. */
 	pc16 = (unsigned short __user *)msk_isa16_mode(regs->cp0_epc);
 	__get_user(halfword, pc16);
 	pc16++;
 	contpc = regs->cp0_epc + 2;
 	word = ((unsigned int)halfword << 16);
 	mminsn.pc_inc = 2;

 	if (!mm_insn_16bit(halfword)) {
 		__get_user(halfword, pc16);
 		pc16++;
 		contpc = regs->cp0_epc + 4;
 		mminsn.pc_inc = 4;
 		word |= halfword;
 	}
 	mminsn.insn = word;

 	if (get_user(halfword, pc16))
 		goto sigsegv;
 	mminsn.next_pc_inc = 2;
 	word = ((unsigned int)halfword << 16);

 	if (!mm_insn_16bit(halfword)) {
 		pc16++;
 		if (get_user(halfword, pc16))
 			goto sigsegv;
 		mminsn.next_pc_inc = 4;
 		word |= halfword;
 	}
 	mminsn.next_insn = word;

 	mm_isBranchInstr(regs, mminsn, &contpc);

 	regs->cp0_epc = contpc;

 	return 0;

 sigsegv:
 	force_sig(SIGSEGV, current);
 	return -EFAULT;
 }

 /*
  * Compute return address and emulate branch in MIPS16e mode after an
  * exception only. It does not handle compact branches/jumps and cannot
  * be used in interrupt context. (Compact branches/jumps do not cause
  * exceptions.)
  */
 int __MIPS16e_compute_return_epc(struct pt_regs *regs)
 {
 	u16 __user *addr;
 	union mips16e_instruction inst;
 	u16 inst2;
 	u32 fullinst;
 	long epc;

 	epc = regs->cp0_epc;

 	/* Read the instruction. */
 	addr = (u16 __user *)msk_isa16_mode(epc);
 	if (__get_user(inst.full, addr)) {
 		force_sig(SIGSEGV, current);
 		return -EFAULT;
 	}

 	switch (inst.ri.opcode) {
 	case MIPS16e_extend_op:
 		regs->cp0_epc += 4;
 		return 0;

 		/*
 		 *  JAL and JALX in MIPS16e mode
 		 */
 	case MIPS16e_jal_op:
 		addr += 1;
 		if (__get_user(inst2, addr)) {
 			force_sig(SIGSEGV, current);
 			return -EFAULT;
 		}
 		fullinst = ((unsigned)inst.full << 16) | inst2;
 		regs->regs[31] = epc + 6;
 		epc += 4;
 		epc >>= 28;
 		epc <<= 28;
 		/*
 		 * JAL:5 X:1 TARGET[20-16]:5 TARGET[25:21]:5 TARGET[15:0]:16
 		 *
 		 * ......TARGET[15:0].................TARGET[20:16]...........
 		 * ......TARGET[25:21]
 		 */
 		epc |=
 		    ((fullinst & 0xffff) << 2) | ((fullinst & 0x3e00000) >> 3) |
 		    ((fullinst & 0x1f0000) << 7);
 		if (!inst.jal.x)
 			set_isa16_mode(epc);	/* Set ISA mode bit. */
 		regs->cp0_epc = epc;
 		return 0;

 		/*
 		 *  J(AL)R(C)
 		 */
 	case MIPS16e_rr_op:
 		if (inst.rr.func == MIPS16e_jr_func) {

 			if (inst.rr.ra)
 				regs->cp0_epc = regs->regs[31];
 			else
 				regs->cp0_epc =
 				    regs->regs[reg16to32[inst.rr.rx]];

 			if (inst.rr.l) {
 				if (inst.rr.nd)
 					regs->regs[31] = epc + 2;
 				else
 					regs->regs[31] = epc + 4;
 			}
 			return 0;
 		}
 		break;
 	}

 	/*
 	 * All other cases have no branch delay slot and are 16-bits.
 	 * Branches do not cause an exception.
 	 */
 	regs->cp0_epc += 2;

 	return 0;
 }

 /**
  * __compute_return_epc_for_insn - Computes the return address and do emulate
  *				    branch simulation, if required.
  *
  * @regs:	Pointer to pt_regs
  * @insn:	branch instruction to decode
  * @returns:	-EFAULT on error and forces SIGBUS, and on success
  *		returns 0 or BRANCH_LIKELY_TAKEN as appropriate after
  *		evaluating the branch.
  */
 int __compute_return_epc_for_insn(struct pt_regs *regs,
 				   union mips_instruction insn)
 {
 	unsigned int bit, fcr31, dspcontrol;
 	long epc = regs->cp0_epc;
 	int ret = 0;

 	switch (insn.i_format.opcode) {
 	/*
 	 * jr and jalr are in r_format format.
 	 */
 	case spec_op:
 		switch (insn.r_format.func) {
 		case jalr_op:
 			regs->regs[insn.r_format.rd] = epc + 8;
 			/* Fall through */
 		case jr_op:
 			regs->cp0_epc = regs->regs[insn.r_format.rs];
 			break;
 		}
 		break;

 	/*
 	 * This group contains:
 	 * bltz_op, bgez_op, bltzl_op, bgezl_op,
 	 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
 	 */
 	case bcond_op:
 		switch (insn.i_format.rt) {
 		case bltz_op:
 		case bltzl_op:
 			if ((long)regs->regs[insn.i_format.rs] < 0) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == bltzl_op)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		case bgez_op:
 		case bgezl_op:
 			if ((long)regs->regs[insn.i_format.rs] >= 0) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == bgezl_op)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		case bltzal_op:
 		case bltzall_op:
 			regs->regs[31] = epc + 8;
 			if ((long)regs->regs[insn.i_format.rs] < 0) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == bltzall_op)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		case bgezal_op:
 		case bgezall_op:
 			regs->regs[31] = epc + 8;
 			if ((long)regs->regs[insn.i_format.rs] >= 0) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == bgezall_op)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		case bposge32_op:
 			if (!cpu_has_dsp)
 				goto sigill;

 			dspcontrol = rddsp(0x01);

 			if (dspcontrol >= 32) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;
 		}
 		break;

 	/*
 	 * These are unconditional and in j_format.
 	 */
 	case jal_op:
 		regs->regs[31] = regs->cp0_epc + 8;
 	case j_op:
 		epc += 4;
 		epc >>= 28;
 		epc <<= 28;
 		epc |= (insn.j_format.target << 2);
 		regs->cp0_epc = epc;
 		if (insn.i_format.opcode == jalx_op)
 			set_isa16_mode(regs->cp0_epc);
 		break;

 	/*
 	 * These are conditional and in i_format.
 	 */
 	case beq_op:
 	case beql_op:
 		if (regs->regs[insn.i_format.rs] ==
 		    regs->regs[insn.i_format.rt]) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 			if (insn.i_format.rt == beql_op)
 				ret = BRANCH_LIKELY_TAKEN;
 		} else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;

 	case bne_op:
 	case bnel_op:
 		if (regs->regs[insn.i_format.rs] !=
 		    regs->regs[insn.i_format.rt]) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 			if (insn.i_format.rt == bnel_op)
 				ret = BRANCH_LIKELY_TAKEN;
 		} else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;

 	case blez_op: /* not really i_format */
 	case blezl_op:
 		/* rt field assumed to be zero */
 		if ((long)regs->regs[insn.i_format.rs] <= 0) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 			if (insn.i_format.rt == bnel_op)
 				ret = BRANCH_LIKELY_TAKEN;
 		} else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;

 	case bgtz_op:
 	case bgtzl_op:
 		/* rt field assumed to be zero */
 		if ((long)regs->regs[insn.i_format.rs] > 0) {
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 			if (insn.i_format.rt == bnel_op)
 				ret = BRANCH_LIKELY_TAKEN;
 		} else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;

 	/*
 	 * And now the FPA/cp1 branch instructions.
 	 */
 	case cop1_op:
 		preempt_disable();
 		if (is_fpu_owner())
 			asm volatile("cfc1\t%0,$31" : "=r" (fcr31));
 		else
 			fcr31 = current->thread.fpu.fcr31;
 		preempt_enable();

 		bit = (insn.i_format.rt >> 2);
 		bit += (bit != 0);
 		bit += 23;
 		switch (insn.i_format.rt & 3) {
 		case 0: /* bc1f */
 		case 2: /* bc1fl */
 			if (~fcr31 & (1 << bit)) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == 2)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;

 		case 1: /* bc1t */
 		case 3: /* bc1tl */
 			if (fcr31 & (1 << bit)) {
 				epc = epc + 4 + (insn.i_format.simmediate << 2);
 				if (insn.i_format.rt == 3)
 					ret = BRANCH_LIKELY_TAKEN;
 			} else
 				epc += 8;
 			regs->cp0_epc = epc;
 			break;
 		}
 		break;
 #ifdef CONFIG_CPU_CAVIUM_OCTEON
 	case lwc2_op: /* This is bbit0 on Octeon */
 		if ((regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
 		     == 0)
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 		else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;
 	case ldc2_op: /* This is bbit032 on Octeon */
 		if ((regs->regs[insn.i_format.rs] &
 		    (1ull<<(insn.i_format.rt+32))) == 0)
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 		else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;
 	case swc2_op: /* This is bbit1 on Octeon */
 		if (regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 		else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;
 	case sdc2_op: /* This is bbit132 on Octeon */
 		if (regs->regs[insn.i_format.rs] &
 		    (1ull<<(insn.i_format.rt+32)))
 			epc = epc + 4 + (insn.i_format.simmediate << 2);
 		else
 			epc += 8;
 		regs->cp0_epc = epc;
 		break;
 #endif
 	}

 	return ret;

 sigill:
 	printk("%s: DSP branch but not DSP ASE - sending SIGBUS.\n", current->comm);
 	force_sig(SIGBUS, current);
 	return -EFAULT;
 }
 EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);

 int __compute_return_epc(struct pt_regs *regs)
 {
 	unsigned int __user *addr;
 	long epc;
 	union mips_instruction insn;

 	epc = regs->cp0_epc;
 	if (epc & 3)
 		goto unaligned;

 	/*
 	 * Read the instruction
 	 */
 	addr = (unsigned int __user *) epc;
 	if (__get_user(insn.word, addr)) {
 		force_sig(SIGSEGV, current);
 		return -EFAULT;
 	}

 	return __compute_return_epc_for_insn(regs, insn);

 unaligned:
 	printk("%s: unaligned epc - sending SIGBUS.\n", current->comm);
 	force_sig(SIGBUS, current);
 	return -EFAULT;
 }
	/*
	* This file is subject to the terms and conditions of the GNU General Public
	* License. See the file "COPYING" in the main directory of this archive
	* for more details.
	*
	* Copyright (C) 1996, 97, 2000, 2001 by Ralf Baechle
	* Copyright (C) 2001 MIPS Technologies, Inc.
	*/
	#include <linux/kernel.h>
	#include <linux/sched.h>
	#include <linux/signal.h>
	#include <linux/module.h>
	#include <asm/branch.h>
	#include <asm/cpu.h>
	#include <asm/cpu-features.h>
	#include <asm/fpu.h>
	#include <asm/fpu_emulator.h>
	#include <asm/inst.h>
	#include <asm/ptrace.h>
	#include <asm/uaccess.h>

	/*
	* Calculate and return exception PC in case of branch delay slot
	* for microMIPS and MIPS16e. It does not clear the ISA mode bit.
	*/
	int __isa_exception_epc(struct pt_regs *regs)
	{
	unsigned short inst;
	long epc = regs->cp0_epc;

	/* Calculate exception PC in branch delay slot. */
	if (__get_user(inst, (u16 __user *) msk_isa16_mode(epc))) {
	/* This should never happen because delay slot was checked. */
	force_sig(SIGSEGV, current);
	return epc;
	}
	if (cpu_has_mips16) {
	if (((union mips16e_instruction)inst).ri.opcode
	== MIPS16e_jal_op)
	epc += 4;
	else
	epc += 2;
	} else if (mm_insn_16bit(inst))
	epc += 2;
	else
	epc += 4;

	return epc;
	}

	/*
	* Compute return address and emulate branch in microMIPS mode after an
	* exception only. It does not handle compact branches/jumps and cannot
	* be used in interrupt context. (Compact branches/jumps do not cause
	* exceptions.)
	*/
	int __microMIPS_compute_return_epc(struct pt_regs *regs)
	{
	u16 __user *pc16;
	u16 halfword;
	unsigned int word;
	unsigned long contpc;
	struct mm_decoded_insn mminsn = { 0 };

	mminsn.micro_mips_mode = 1;

	/* This load never faults. */
	pc16 = (unsigned short __user *)msk_isa16_mode(regs->cp0_epc);
	__get_user(halfword, pc16);
	pc16++;
	contpc = regs->cp0_epc + 2;
	word = ((unsigned int)halfword << 16);
	mminsn.pc_inc = 2;

	if (!mm_insn_16bit(halfword)) {
	__get_user(halfword, pc16);
	pc16++;
	contpc = regs->cp0_epc + 4;
	mminsn.pc_inc = 4;
	word \|= halfword;
	}
	mminsn.insn = word;

	if (get_user(halfword, pc16))
	goto sigsegv;
	mminsn.next_pc_inc = 2;
	word = ((unsigned int)halfword << 16);

	if (!mm_insn_16bit(halfword)) {
	pc16++;
	if (get_user(halfword, pc16))
	goto sigsegv;
	mminsn.next_pc_inc = 4;
	word \|= halfword;
	}
	mminsn.next_insn = word;

	mm_isBranchInstr(regs, mminsn, &contpc);

	regs->cp0_epc = contpc;

	return 0;

	sigsegv:
	force_sig(SIGSEGV, current);
	return -EFAULT;
	}

	/*
	* Compute return address and emulate branch in MIPS16e mode after an
	* exception only. It does not handle compact branches/jumps and cannot
	* be used in interrupt context. (Compact branches/jumps do not cause
	* exceptions.)
	*/
	int __MIPS16e_compute_return_epc(struct pt_regs *regs)
	{
	u16 __user *addr;
	union mips16e_instruction inst;
	u16 inst2;
	u32 fullinst;
	long epc;

	epc = regs->cp0_epc;

	/* Read the instruction. */
	addr = (u16 __user *)msk_isa16_mode(epc);
	if (__get_user(inst.full, addr)) {
	force_sig(SIGSEGV, current);
	return -EFAULT;
	}

	switch (inst.ri.opcode) {
	case MIPS16e_extend_op:
	regs->cp0_epc += 4;
	return 0;

	/*
	* JAL and JALX in MIPS16e mode
	*/
	case MIPS16e_jal_op:
	addr += 1;
	if (__get_user(inst2, addr)) {
	force_sig(SIGSEGV, current);
	return -EFAULT;
	}
	fullinst = ((unsigned)inst.full << 16) \| inst2;
	regs->regs[31] = epc + 6;
	epc += 4;
	epc >>= 28;
	epc <<= 28;
	/*
	* JAL:5 X:1 TARGET[20-16]:5 TARGET[25:21]:5 TARGET[15:0]:16
	*
	* ......TARGET[15:0].................TARGET[20:16]...........
	* ......TARGET[25:21]
	*/
	epc \|=
	((fullinst & 0xffff) << 2) \| ((fullinst & 0x3e00000) >> 3) \|
	((fullinst & 0x1f0000) << 7);
	if (!inst.jal.x)
	set_isa16_mode(epc); /* Set ISA mode bit. */
	regs->cp0_epc = epc;
	return 0;

	/*
	* J(AL)R(C)
	*/
	case MIPS16e_rr_op:
	if (inst.rr.func == MIPS16e_jr_func) {

	if (inst.rr.ra)
	regs->cp0_epc = regs->regs[31];
	else
	regs->cp0_epc =
	regs->regs[reg16to32[inst.rr.rx]];

	if (inst.rr.l) {
	if (inst.rr.nd)
	regs->regs[31] = epc + 2;
	else
	regs->regs[31] = epc + 4;
	}
	return 0;
	}
	break;
	}

	/*
	* All other cases have no branch delay slot and are 16-bits.
	* Branches do not cause an exception.
	*/
	regs->cp0_epc += 2;

	return 0;
	}

	/**
	* __compute_return_epc_for_insn - Computes the return address and do emulate
	* branch simulation, if required.
	*
	* @regs: Pointer to pt_regs
	* @insn: branch instruction to decode
	* @returns: -EFAULT on error and forces SIGBUS, and on success
	* returns 0 or BRANCH_LIKELY_TAKEN as appropriate after
	* evaluating the branch.
	*/
	int __compute_return_epc_for_insn(struct pt_regs *regs,
	union mips_instruction insn)
	{
	unsigned int bit, fcr31, dspcontrol;
	long epc = regs->cp0_epc;
	int ret = 0;

	switch (insn.i_format.opcode) {
	/*
	* jr and jalr are in r_format format.
	*/
	case spec_op:
	switch (insn.r_format.func) {
	case jalr_op:
	regs->regs[insn.r_format.rd] = epc + 8;
	/* Fall through */
	case jr_op:
	regs->cp0_epc = regs->regs[insn.r_format.rs];
	break;
	}
	break;

	/*
	* This group contains:
	* bltz_op, bgez_op, bltzl_op, bgezl_op,
	* bltzal_op, bgezal_op, bltzall_op, bgezall_op.
	*/
	case bcond_op:
	switch (insn.i_format.rt) {
	case bltz_op:
	case bltzl_op:
	if ((long)regs->regs[insn.i_format.rs] < 0) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == bltzl_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case bgez_op:
	case bgezl_op:
	if ((long)regs->regs[insn.i_format.rs] >= 0) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == bgezl_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case bltzal_op:
	case bltzall_op:
	regs->regs[31] = epc + 8;
	if ((long)regs->regs[insn.i_format.rs] < 0) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == bltzall_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case bgezal_op:
	case bgezall_op:
	regs->regs[31] = epc + 8;
	if ((long)regs->regs[insn.i_format.rs] >= 0) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == bgezall_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case bposge32_op:
	if (!cpu_has_dsp)
	goto sigill;

	dspcontrol = rddsp(0x01);

	if (dspcontrol >= 32) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	}
	break;

	/*
	* These are unconditional and in j_format.
	*/
	case jal_op:
	regs->regs[31] = regs->cp0_epc + 8;
	case j_op:
	epc += 4;
	epc >>= 28;
	epc <<= 28;
	epc \|= (insn.j_format.target << 2);
	regs->cp0_epc = epc;
	if (insn.i_format.opcode == jalx_op)
	set_isa16_mode(regs->cp0_epc);
	break;

	/*
	* These are conditional and in i_format.
	*/
	case beq_op:
	case beql_op:
	if (regs->regs[insn.i_format.rs] ==
	regs->regs[insn.i_format.rt]) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == beql_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case bne_op:
	case bnel_op:
	if (regs->regs[insn.i_format.rs] !=
	regs->regs[insn.i_format.rt]) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == bnel_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case blez_op: /* not really i_format */
	case blezl_op:
	/* rt field assumed to be zero */
	if ((long)regs->regs[insn.i_format.rs] <= 0) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == bnel_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case bgtz_op:
	case bgtzl_op:
	/* rt field assumed to be zero */
	if ((long)regs->regs[insn.i_format.rs] > 0) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == bnel_op)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	/*
	* And now the FPA/cp1 branch instructions.
	*/
	case cop1_op:
	preempt_disable();
	if (is_fpu_owner())
	asm volatile("cfc1\t%0,$31" : "=r" (fcr31));
	else
	fcr31 = current->thread.fpu.fcr31;
	preempt_enable();

	bit = (insn.i_format.rt >> 2);
	bit += (bit != 0);
	bit += 23;
	switch (insn.i_format.rt & 3) {
	case 0: /* bc1f */
	case 2: /* bc1fl */
	if (~fcr31 & (1 << bit)) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == 2)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;

	case 1: /* bc1t */
	case 3: /* bc1tl */
	if (fcr31 & (1 << bit)) {
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	if (insn.i_format.rt == 3)
	ret = BRANCH_LIKELY_TAKEN;
	} else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	}
	break;
	#ifdef CONFIG_CPU_CAVIUM_OCTEON
	case lwc2_op: /* This is bbit0 on Octeon */
	if ((regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
	== 0)
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	case ldc2_op: /* This is bbit032 on Octeon */
	if ((regs->regs[insn.i_format.rs] &
	(1ull<<(insn.i_format.rt+32))) == 0)
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	case swc2_op: /* This is bbit1 on Octeon */
	if (regs->regs[insn.i_format.rs] & (1ull<<insn.i_format.rt))
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	case sdc2_op: /* This is bbit132 on Octeon */
	if (regs->regs[insn.i_format.rs] &
	(1ull<<(insn.i_format.rt+32)))
	epc = epc + 4 + (insn.i_format.simmediate << 2);
	else
	epc += 8;
	regs->cp0_epc = epc;
	break;
	#endif
	}

	return ret;

	sigill:
	printk("%s: DSP branch but not DSP ASE - sending SIGBUS.\n", current->comm);
	force_sig(SIGBUS, current);
	return -EFAULT;
	}
	EXPORT_SYMBOL_GPL(__compute_return_epc_for_insn);

	int __compute_return_epc(struct pt_regs *regs)
	{
	unsigned int __user *addr;
	long epc;
	union mips_instruction insn;

	epc = regs->cp0_epc;
	if (epc & 3)
	goto unaligned;

	/*
	* Read the instruction
	*/
	addr = (unsigned int __user *) epc;
	if (__get_user(insn.word, addr)) {
	force_sig(SIGSEGV, current);
	return -EFAULT;
	}

	return __compute_return_epc_for_insn(regs, insn);

	unaligned:
	printk("%s: unaligned epc - sending SIGBUS.\n", current->comm);
	force_sig(SIGBUS, current);
	return -EFAULT;
	}