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

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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>
This commit is contained in:
Markos Chandras 2014-11-26 12:57:54 +00:00
parent c8a34581ec
commit a8ff66f52d
2 changed files with 55 additions and 0 deletions
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31
arch/mips/kernel/branch.c
View File

@ -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);

24
arch/mips/math-emu/cp1emu.c
View File

@ -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 +