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JitArm64: Fix CoreTiming contract 

Call Advance at the start of each timing slice instead of the end.

Possibly fixed a bug where a slice would randomly branch straight
back to Advance() because the flags were not set to the right
values before branching to the dispatcher entrypoint.
This commit is contained in:
EmptyChaos 2016-09-12 09:08:56 +00:00
parent f5bfce657c
commit 55a7f576aa
1 changed files with 25 additions and 15 deletions
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40
Source/Core/Core/PowerPC/JitArm64/JitAsm.cpp
View File

@ -28,18 +28,28 @@ void JitArm64::GenerateAsm()
MOVP2R(PPC_REG, &PowerPC::ppcState);
// Load the current PC into DISPATCHER_PC
LDR(INDEX_UNSIGNED, DISPATCHER_PC, PPC_REG, PPCSTATE_OFF(pc));
FixupBranch to_dispatcher = B();
// The PC will be loaded into DISPATCHER_PC after the call to CoreTiming::Advance().
// Advance() does an exception check so we don't know what PC to use until afterwards.
FixupBranch to_start_of_timing_slice = B();
// If we align the dispatcher to a page then we can load its location with one ADRP instruction
// do
// {
// CoreTiming::Advance(); // <-- Checks for exceptions (changes PC)
// DISPATCHER_PC = PC;
// do
// {
// dispatcherNoCheck:
// ExecuteBlock(JitBase::Dispatch());
// dispatcher:
// } while (PowerPC::ppcState.downcount > 0);
// doTiming:
// NPC = PC = DISPATCHER_PC;
// } while (CPU::GetState() == CPU::CPU_RUNNING);
AlignCodePage();
dispatcher = GetCodePtr();
WARN_LOG(DYNA_REC, "Dispatcher is %p\n", dispatcher);
SetJumpTarget(to_dispatcher);
// Downcount Check
// The result of slice decrementation should be in flags if somebody jumped here
// IMPORTANT - We jump on negative, not carry!!!
@ -119,12 +129,6 @@ void JitArm64::GenerateAsm()
STR(INDEX_UNSIGNED, DISPATCHER_PC, PPC_REG, PPCSTATE_OFF(pc));
STR(INDEX_UNSIGNED, DISPATCHER_PC, PPC_REG, PPCSTATE_OFF(npc));
MOVP2R(X30, &CoreTiming::Advance);
BLR(X30);
// Load the PC back into DISPATCHER_PC (the exception handler might have changed it)
LDR(INDEX_UNSIGNED, DISPATCHER_PC, PPC_REG, PPCSTATE_OFF(pc));
// Check the state pointer to see if we are exiting
// Gets checked on at the end of every slice
MOVP2R(X0, CPU::GetStatePtr());
@ -133,11 +137,17 @@ void JitArm64::GenerateAsm()
CMP(W0, 0);
FixupBranch Exit = B(CC_NEQ);
B(dispatcher);
SetJumpTarget(to_start_of_timing_slice);
MOVP2R(X30, &CoreTiming::Advance);
BLR(X30);
// Load the PC back into DISPATCHER_PC (the exception handler might have changed it)
LDR(INDEX_UNSIGNED, DISPATCHER_PC, PPC_REG, PPCSTATE_OFF(pc));
// We can safely assume that downcount >= 1
B(dispatcherNoCheck);
SetJumpTarget(Exit);
STR(INDEX_UNSIGNED, DISPATCHER_PC, PPC_REG, PPCSTATE_OFF(pc));
ABI_PopRegisters(regs_to_save);
RET(X30);