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backend/EmitX64: Handle new_pc<1:0> == '10' case in BXWritePC

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This commit is contained in:
MerryMage 2016-07-18 20:01:48 +01:00
parent 14dcb18bbe
commit 8a310777a1
1 changed files with 20 additions and 23 deletions
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43
src/backend_x64/emit_x64.cpp
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@ -222,32 +222,29 @@ void EmitX64::EmitBXWritePC(IR::Value* value_) {
auto value = reinterpret_cast<IR::Inst*>(value_);
X64Reg new_pc = reg_alloc.UseRegister(value->GetArg(0).get());
X64Reg tmp = reg_alloc.ScratchRegister();
X64Reg cpsr = reg_alloc.ScratchRegister();
X64Reg tmp1 = reg_alloc.ScratchRegister();
X64Reg tmp2 = reg_alloc.ScratchRegister();
// Note: new_pc<1:0> == '10' is UNPREDICTABLE
// Pseudocode:
// if (new_pc & 1) {
// new_pc &= 0xFFFFFFFE;
// cpsr.T = true;
// } else {
// new_pc &= 0xFFFFFFFC;
// cpsr.T = false;
// }
// Alternative implementations
#if 0
code->MOV(32, R(tmp), MJitStateCpsr());
code->MOV(32, R(cpsr), R(tmp));
code->OR(32, R(tmp), Imm32(1 << 5));
code->AND(32, R(cpsr), Imm32(~(1 << 5)));
code->BTR(32, R(new_pc), Imm8(0));
code->CMOVcc(32, cpsr, R(tmp), CC_C);
code->MOV(32, R(tmp1), MJitStateCpsr());
code->MOV(32, R(tmp2), R(tmp1));
code->AND(32, R(tmp2), Imm32(~(1 << 5))); // CPSR.T = 0
code->OR(32, R(tmp1), Imm32(1 << 5)); // CPSR.T = 1
code->TEST(8, R(new_pc), Imm8(1));
code->CMOVcc(32, tmp1, R(tmp2), CC_E); // CPSR.T = pc & 1
code->MOV(32, MJitStateCpsr(), R(tmp1));
code->LEA(32, tmp2, MComplex(new_pc, new_pc, 1, 0));
code->OR(32, R(tmp2), Imm32(0xFFFFFFFC)); // tmp2 = pc & 1 ? 0xFFFFFFFE : 0xFFFFFFFC
code->AND(32, R(new_pc), R(tmp2));
code->MOV(32, MJitStateReg(Arm::Reg::PC), R(new_pc));
code->MOV(32, MJitStateCpsr(), R(cpsr));
#else
code->MOV(32, R(tmp), R(new_pc));
code->AND(32, R(tmp), Imm8(1));
code->AND(32, R(new_pc), Imm32(0xFFFFFFFE));
code->MOV(32, R(cpsr), MJitStateCpsr());
code->SHL(32, R(tmp), Imm8(5));
code->AND(32, R(cpsr), Imm32(~(1 << 5)));
code->OR(32, R(cpsr), R(tmp));
code->MOV(32, MJitStateReg(Arm::Reg::PC), R(new_pc));
code->MOV(32, MJitStateCpsr(), R(cpsr));
#endif
}
void EmitX64::EmitCallSupervisor(IR::Value* value_) {