mipssim.cc File Reference

Function Documentation

void Mult	(	int	a,
		int	b,
		bool	signedArith,
		int *	hiPtr,
		int *	loPtr
	)	`[static]`

Definition at line 636 of file mipssim.cc.

References FALSE.

Referenced by Machine::OneInstruction.

00637 {
00638     if ((a == 0) || (b == 0)) {
00639         *hiPtr = *loPtr = 0;
00640         return;
00641     }
00642 
00643     // Compute the sign of the result, then make everything positive
00644     // so unsigned computation can be done in the main loop.
00645     bool negative = FALSE;
00646     if (signedArith) {
00647         if (a < 0) {
00648             negative = !negative;
00649             a = -a;
00650         }
00651         if (b < 0) {
00652             negative = !negative;
00653             b = -b;
00654         }
00655     }
00656 
00657     // Compute the result in unsigned arithmetic (check a's bits one at
00658     // a time, and add in a shifted value of b).
00659     unsigned int bLo = b;
00660     unsigned int bHi = 0;
00661     unsigned int lo = 0;
00662     unsigned int hi = 0;
00663     for (int i = 0; i < 32; i++) {
00664         if (a & 1) {
00665             lo += bLo;
00666             if (lo < bLo)  // Carry out of the low bits?
00667                 hi += 1;
00668             hi += bHi;
00669             if ((a & 0xfffffffe) == 0)
00670                 break;
00671         }
00672         bHi <<= 1;
00673         if (bLo & 0x80000000)
00674             bHi |= 1;
00675         
00676         bLo <<= 1;
00677         a >>= 1;
00678     }
00679 
00680     // If the result is supposed to be negative, compute the two's
00681     // complement of the double-word result.
00682     if (negative) {
00683         hi = ~hi;
00684         lo = ~lo;
00685         lo++;
00686         if (lo == 0)
00687             hi++;
00688     }
00689     
00690     *hiPtr = (int) hi;
00691     *loPtr = (int) lo;
00692 }

int TypeToReg	(	RegType	reg,
		Instruction *	instr
	)	`[static]`

Definition at line 54 of file mipssim.cc.

References Instruction::extra, EXTRA, Instruction::rd, RD, RegType, Instruction::rs, RS, Instruction::rt, and RT.

Referenced by Machine::OneInstruction.

00055 {
00056     switch (reg) {
00057       case RS:
00058         return instr->rs;
00059       case RT:
00060         return instr->rt;
00061       case RD:
00062         return instr->rd;
00063       case EXTRA:
00064         return instr->extra;
00065       default:
00066         return -1;
00067     }
00068 }

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Functions
void	Mult (int a, int b, bool signedArith, int hiPtr, int loPtr)
int	TypeToReg (RegType reg, Instruction *instr)

mipssim.cc File Reference

Functions

Function Documentation