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armemu: Fix underflows in USAD8/USADA8

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Initially reported by xdec.
This commit is contained in:
Lioncash 2014-12-28 06:07:24 -05:00
parent 28e64806cd
commit 059c65a27a
3 changed files with 14 additions and 4 deletions
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8
src/core/arm/interpreter/armemu.cpp
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@ -6643,10 +6643,10 @@ L_stm_s_takeabort:
const u32 rm_val = state->Reg[rm_idx];
const u32 rn_val = state->Reg[rn_idx];
const u8 diff1 = (u8)std::labs((rn_val & 0xFF) - (rm_val & 0xFF));
const u8 diff2 = (u8)std::labs(((rn_val >> 8) & 0xFF) - ((rm_val >> 8) & 0xFF));
const u8 diff3 = (u8)std::labs(((rn_val >> 16) & 0xFF) - ((rm_val >> 16) & 0xFF));
const u8 diff4 = (u8)std::labs(((rn_val >> 24) & 0xFF) - ((rm_val >> 24) & 0xFF));
const u8 diff1 = ARMul_UnsignedAbsoluteDifference(rn_val & 0xFF, rm_val & 0xFF);
const u8 diff2 = ARMul_UnsignedAbsoluteDifference((rn_val >> 8) & 0xFF, (rm_val >> 8) & 0xFF);
const u8 diff3 = ARMul_UnsignedAbsoluteDifference((rn_val >> 16) & 0xFF, (rm_val >> 16) & 0xFF);
const u8 diff4 = ARMul_UnsignedAbsoluteDifference((rn_val >> 24) & 0xFF, (rm_val >> 24) & 0xFF);
u32 finalDif = (diff1 + diff2 + diff3 + diff4);

9
src/core/arm/interpreter/armsupp.cpp
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@ -392,6 +392,15 @@ ARMul_NthReg (ARMword instr, unsigned number)
return (bit - 1);
}
/* Unsigned sum of absolute difference */
u8 ARMul_UnsignedAbsoluteDifference(u8 left, u8 right)
{
if (left > right)
return left - right;
return right - left;
}
/* Assigns the N and Z flags depending on the value of result. */
void

1
src/core/arm/skyeye_common/armemu.h
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@ -600,6 +600,7 @@ extern ARMword ARMul_SwitchMode (ARMul_State *, ARMword, ARMword);
extern ARMword ARMul_Align (ARMul_State *, ARMword, ARMword);
extern ARMword ARMul_SwitchMode (ARMul_State *, ARMword, ARMword);
extern void ARMul_MSRCpsr (ARMul_State *, ARMword, ARMword);
extern u8 ARMul_UnsignedAbsoluteDifference(u8, u8);
extern void ARMul_SubOverflow (ARMul_State *, ARMword, ARMword, ARMword);
extern void ARMul_AddOverflow (ARMul_State *, ARMword, ARMword, ARMword);
extern void ARMul_AddOverflowQ(ARMul_State*, ARMword, ARMword);