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JIT: revert accuracy improvement to mftb 

Fixes a few games (e.g. Karaoke Revolution Party) for reasons explained in the
comments.
This commit is contained in:
Fiora 2014-11-10 20:10:41 -08:00
parent 974dd21019
commit 4b105ed0e4
1 changed files with 7 additions and 3 deletions
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10
Source/Core/Core/PowerPC/Jit64/Jit_SystemRegisters.cpp
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@ -232,9 +232,13 @@ void Jit64::mfspr(UGeckoInstruction inst)
// cost of calling out to C for this is actually significant. // cost of calling out to C for this is actually significant.
MOV(64, R(RAX), M(&CoreTiming::globalTimer)); MOV(64, R(RAX), M(&CoreTiming::globalTimer));
SUB(64, R(RAX), M(&CoreTiming::fakeTBStartTicks)); SUB(64, R(RAX), M(&CoreTiming::fakeTBStartTicks));
// The timer can change within a long block, so add in any difference // It might seem convenient to correct the timer for the block position here for even more accurate
if (js.downcountAmount) // timing, but as of currently, this can break games. If we end up reading a time *after* the time
ADD(64, R(RAX), Imm32(js.downcountAmount)); // at which an interrupt was supposed to occur, e.g. because we're 100 cycles into a block with only
// 50 downcount remaining, some games don't function correctly, such as Karaoke Party Revolution,
// which won't get past the loading screen.
//if (js.downcountAmount)
// ADD(64, R(RAX), Imm32(js.downcountAmount));
// a / 12 = (a * 0xAAAAAAAAAAAAAAAB) >> 67 // a / 12 = (a * 0xAAAAAAAAAAAAAAAB) >> 67
MOV(64, R(RDX), Imm64(0xAAAAAAAAAAAAAAABULL)); MOV(64, R(RDX), Imm64(0xAAAAAAAAAAAAAAABULL));
MUL(64, R(RDX)); MUL(64, R(RDX));