MIPS: Emulate the BC1{EQ,NE}Z FPU instructions

MIPS R6 introduced the following two branch instructions for COP1:

BC1EQZ: Branch if Cop1 (FPR) Register Bit 0 is Equal to Zero
BC1NEZ: Branch if Cop1 (FPR) Register Bit 0 is Not Equal to Zero

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

diff --git a/arch/mips/include/uapi/asm/inst.h b/arch/mips/include/uapi/asm/inst.h
index 5c9e14a..19d3bc1 100644 (file)
--- a/arch/mips/include/uapi/asm/inst.h
+++ b/arch/mips/include/uapi/asm/inst.h
@@ -115,7 +115,8 @@ enum cop_op {
        mfhc_op       = 0x03, mtc_op        = 0x04,
        dmtc_op       = 0x05, ctc_op        = 0x06,
        mthc0_op      = 0x06, mthc_op       = 0x07,
-       bc_op         = 0x08, cop_op        = 0x10,
+       bc_op         = 0x08, bc1eqz_op     = 0x09,
+       bc1nez_op     = 0x0d, cop_op        = 0x10,
        copm_op       = 0x18
 };
 

diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index 5121ada..f9cb13c 100644 (file)
--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -403,7 +403,7 @@ int __MIPS16e_compute_return_epc(struct pt_regs *regs)
 int __compute_return_epc_for_insn(struct pt_regs *regs,
                                   union mips_instruction insn)
 {
-       unsigned int bit, fcr31, dspcontrol;
+       unsigned int bit, fcr31, dspcontrol, reg;
        long epc = regs->cp0_epc;
        int ret = 0;
 
@@ -618,40 +618,83 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
         * And now the FPA/cp1 branch instructions.
         */
        case cop1_op:
-               preempt_disable();
-               if (is_fpu_owner())
-                       fcr31 = read_32bit_cp1_register(CP1_STATUS);
-               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
+               if (cpu_has_mips_r6 &&
+                   ((insn.i_format.rs == bc1eqz_op) ||
+                    (insn.i_format.rs == bc1nez_op))) {
+                       if (!used_math()) { /* First time FPU user */
+                               ret = init_fpu();
+                               if (ret && NO_R6EMU) {
+                                       ret = -ret;
+                                       break;
+                               }
+                               ret = 0;
+                               set_used_math();
+                       }
+                       lose_fpu(1);    /* Save FPU state for the emulator. */
+                       reg = insn.i_format.rt;
+                       bit = 0;
+                       switch (insn.i_format.rs) {
+                       case bc1eqz_op:
+                               /* Test bit 0 */
+                               if (get_fpr32(&current->thread.fpu.fpr[reg], 0)
+                                   & 0x1)
+                                       bit = 1;
+                               break;
+                       case bc1nez_op:
+                               /* Test bit 0 */
+                               if (!(get_fpr32(&current->thread.fpu.fpr[reg], 0)
+                                     & 0x1))
+                                       bit = 1;
+                               break;
+                       }
+                       own_fpu(1);
+                       if (bit)
+                               epc = epc + 4 +
+                                       (insn.i_format.simmediate << 2);
+                       else
                                epc += 8;
                        regs->cp0_epc = epc;
+
                        break;
+               } else {
 
-               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;
+                       preempt_disable();
+                       if (is_fpu_owner())
+                               fcr31 = read_32bit_cp1_register(CP1_STATUS);
+                       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;
                }
-               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))

diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c
index 7bbaefe..798204e 100644 (file)
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -602,6 +602,33 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 #endif
        case cop0_op:
        case cop1_op:
+               /* Need to check for R6 bc1nez and bc1eqz branches */
+               if (cpu_has_mips_r6 &&
+                   ((insn.i_format.rs == bc1eqz_op) ||
+                    (insn.i_format.rs == bc1nez_op))) {
+                       bit = 0;
+                       switch (insn.i_format.rs) {
+                       case bc1eqz_op:
+                               if (get_fpr32(&current->thread.fpu.fpr[insn.i_format.rt], 0) & 0x1)
+                                   bit = 1;
+                               break;
+                       case bc1nez_op:
+                               if (!(get_fpr32(&current->thread.fpu.fpr[insn.i_format.rt], 0) & 0x1))
+                                   bit = 1;
+                               break;
+                       }
+                       if (bit)
+                               *contpc = regs->cp0_epc +
+                                       dec_insn.pc_inc +
+                                       (insn.i_format.simmediate << 2);
+                       else
+                               *contpc = regs->cp0_epc +
+                                       dec_insn.pc_inc +
+                                       dec_insn.next_pc_inc;
+
+                       return 1;
+               }
+               /* R2/R6 compatible cop1 instruction. Fall through */
        case cop2_op:
        case cop1x_op:
                if (insn.i_format.rs == bc_op) {