MIPS: Emulate the new MIPS R6 B{L,G}T{Z,}{AL,}C instructions

MIPS R6 added the following four instructions which share the
BGTZ and BGTZL opcode:

BLTZALC: Compact branch-and-link if GPR rt is < to zero
BGTZALC: Compact branch-and-link if GPR rt is > to zero
BLTZL  : Compact branch if GPR rt is < to zero
BGTZL  : Compact branch if GPR rt is > to zero
BLTC   : Compact branch if GPR rs is less than GPR rt
BLTUC  : Similar to BLTC but unsigned

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

1 files changed, 22 insertions, 0 deletions

diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index a1fd8786d716..cd880b91f092 100644
--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -635,6 +635,28 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
                 if (NO_R6EMU)
                         goto sigill_r6;
         case bgtz_op:
+                /*
+                 * Compact branches for R6 for the
+                 * bgtz and bgtzl opcodes.
+                 * BGTZ  | rs = 0 | rt != 0  == BGTZALC
+                 * BGTZ  | rs = rt != 0      == BLTZALC
+                 * BGTZ  | rs != 0 | rt != 0 == BLTUC
+                 * BGTZL | rs = 0 | rt != 0  == BGTZC
+                 * BGTZL | rs = rt != 0      == BLTZC
+                 * BGTZL | rs != 0 | rt != 0 == BLTC
+                 *
+                 * *ZALC varint for BGTZ &&& rt != 0
+                 * For real GTZ{,L}, rt is always 0.
+                 */
+                if (cpu_has_mips_r6 && insn.i_format.rt) {
+                        if ((insn.i_format.opcode == blez_op) &&
+                            ((!insn.i_format.rs && insn.i_format.rt) ||
+                            (insn.i_format.rs == insn.i_format.rt)))
+                                regs->regs[31] = epc + 4;
+                        regs->cp0_epc += 8;
+                        break;
+                }
+
                 /* rt field assumed to be zero */
                 if ((long)regs->regs[insn.i_format.rs] > 0) {
                         epc = epc + 4 + (insn.i_format.simmediate << 2);