diff options
| author | Markos Chandras <markos.chandras@imgtec.com> | 2014-11-26 12:57:54 +0000 |
|---|---|---|
| committer | Markos Chandras <markos.chandras@imgtec.com> | 2015-02-17 15:37:33 +0000 |
| commit | a8ff66f52d3f17b5ae793955270675c197f73d6c (patch) | |
| tree | ae86a8dfde65eecdcd9bd7591034ef5f65a65997 /arch/mips | |
| parent | c8a34581ec09a5ee11dd833d6c5cf41fdbef706f (diff) | |
MIPS: Emulate the new MIPS R6 B{L,G}Ε{Z,}{AL,}C instructions
MIPS R6 added the following four instructions which share the
BLEZ and BLEZL opcodes:
BLEZALC: Compact branch-and-link if GPR rt is <= to zero
BGEZALC: Compact branch-and-link if GPR rt is >= to zero
BLEZC : Compact branch if GPR rt is <= to zero
BGEZC : Compact branch if GPR rt is >= to zero
BGEC : Compact branch if GPR rs is less than or equal to GPR rt
BGEUC : Similar to BGEC but unsigned.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Diffstat (limited to 'arch/mips')
| -rw-r--r-- | arch/mips/kernel/branch.c | 31 | ||||
| -rw-r--r-- | arch/mips/math-emu/cp1emu.c | 24 |
2 files changed, 55 insertions, 0 deletions
diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c index f9cb13c56595..a1fd8786d716 100644 --- a/arch/mips/kernel/branch.c +++ b/arch/mips/kernel/branch.c @@ -399,6 +399,16 @@ int __MIPS16e_compute_return_epc(struct pt_regs *regs) * @returns: -EFAULT on error and forces SIGBUS, and on success * returns 0 or BRANCH_LIKELY_TAKEN as appropriate after * evaluating the branch. + * + * MIPS R6 Compact branches and forbidden slots: + * Compact branches do not throw exceptions because they do + * not have delay slots. The forbidden slot instruction ($PC+4) + * is only executed if the branch was not taken. Otherwise the + * forbidden slot is skipped entirely. This means that the + * only possible reason to be here because of a MIPS R6 compact + * branch instruction is that the forbidden slot has thrown one. + * In that case the branch was not taken, so the EPC can be safely + * set to EPC + 8. */ int __compute_return_epc_for_insn(struct pt_regs *regs, union mips_instruction insn) @@ -590,6 +600,27 @@ int __compute_return_epc_for_insn(struct pt_regs *regs, if (NO_R6EMU) goto sigill_r6; case blez_op: + /* + * Compact branches for R6 for the + * blez and blezl opcodes. + * BLEZ | rs = 0 | rt != 0 == BLEZALC + * BLEZ | rs = rt != 0 == BGEZALC + * BLEZ | rs != 0 | rt != 0 == BGEUC + * BLEZL | rs = 0 | rt != 0 == BLEZC + * BLEZL | rs = rt != 0 == BGEZC + * BLEZL | rs != 0 | rt != 0 == BGEC + * + * For real BLEZ{,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); diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c index 798204e492fc..c770617dc340 100644 --- a/arch/mips/math-emu/cp1emu.c +++ b/arch/mips/math-emu/cp1emu.c @@ -552,6 +552,30 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, if (NO_R6EMU) break; case blez_op: + + /* + * Compact branches for R6 for the + * blez and blezl opcodes. + * BLEZ | rs = 0 | rt != 0 == BLEZALC + * BLEZ | rs = rt != 0 == BGEZALC + * BLEZ | rs != 0 | rt != 0 == BGEUC + * BLEZL | rs = 0 | rt != 0 == BLEZC + * BLEZL | rs = rt != 0 == BGEZC + * BLEZL | rs != 0 | rt != 0 == BGEC + * + * For real BLEZ{,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] = regs->cp0_epc + + dec_insn.pc_inc; + *contpc = regs->cp0_epc + dec_insn.pc_inc + + dec_insn.next_pc_inc; + + return 1; + } if ((long)regs->regs[insn.i_format.rs] <= 0) *contpc = regs->cp0_epc + dec_insn.pc_inc + |