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DSPLLE: Add a comment describing my latest unverified theory: that 'l and the other opcode extensions might be meant to sign extend the loaded value in some cases. 

git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@4811 8ced0084-cf51-0410-be5f-012b33b47a6e
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hrydgard 2010-01-12 00:38:54 +00:00
parent 9012d4f4b8
commit 573a7f4d6e
1 changed files with 15 additions and 0 deletions
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15
Source/Core/DSPCore/Src/DSPIntUtil.h
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@ -140,6 +140,21 @@ inline void dsp_op_write_reg(int reg, u16 val)
g_dsp.r[reg] = (u16)(s16)(s8)(u8)val;
break;
case DSP_REG_ACM0:
case DSP_REG_ACM1:
g_dsp.r[reg] = val;
// Enabling the below sign extension code breaks things.
// There's probably some condition that enable it, maybe one of
// the status flags like M2.
// Or maybe it only happens when this call is a result of 'l and similar extended opcodes.
// Sign extend the loaded register. ACM0
// g_dsp.r[reg - DSP_REG_ACM0 + DSP_REG_ACH0] = ((s16)val < 0 ? 0xFFFF : 0);
// g_dsp.r[reg - DSP_REG_ACM0 + DSP_REG_ACL0] = 0; // ?
break;
// There might also be something similar for AX.L but I'm not at all sure about that.
// Stack registers.
case DSP_REG_ST0:
case DSP_REG_ST1: