// // Copyright (C) 1997,1998,1999 Forest Edge Software, see License.txt for Rights // // Program: eVAX, a "Virtual VAX" // // Author: Tom Cole // // Module: emul_float_math.c // // Purpose: Emulator handlers for floating ponit math instructions // // This single routine handles all F_FLOAT and D_FLOAT math // instructions. This routine examines the opcode to determine // what the data size and type is, and whether to write back // to the second or third operand (ADDF2 vs. ADDF3, etc.). // // History: 09/07/98 Initial implementation. // // 10/15/99 Fix bug is selection of integer data size // for conversions. // #include "vax.pch" #include "fpu.h" EMULATOR_ENTRY( emul_float_math ) { char * src1, *src2; LONGWORD data, d1, d2, rc; double float1, float2, float3; unsigned char op, dsize, dsize2, opcnt, func; // Get address of source data (from memory or from register). Note // that this might cause a page fault. If so, then the get returns // a null pointer. In that case, return a fault return code. src1 = ( char * ) get_operand( opcode, 0, OP_RD ); if( src1 == 0L ) return VAX_FAULT; src2 = ( char * ) get_operand( opcode, 1, OP_RD ); if( src2 == 0L ) return VAX_FAULT; /* The instructions are structured like this: 0 1 0 0 - - - - ---F- 0 1 0 0 0 0 0 0 ADDF2 0 1 0 0 0 0 0 1 ADDF3 0 1 0 0 0 0 1 0 SUBF2 0 1 0 0 0 0 1 1 SUBF3 0 1 0 0 0 1 0 0 MULF2 0 1 0 0 0 1 0 1 MULF3 0 1 0 0 0 1 1 0 DIVF2 0 1 0 0 0 1 1 1 DIVF3 0 1 0 0 1 0 0 0 CVTFB 0 1 0 0 1 0 0 1 CVTFW 0 1 0 0 1 0 1 0 CVTFL 0 1 0 0 1 0 1 1 CVTRFL 0 1 0 0 1 1 0 0 CVTBF 0 1 0 0 1 1 0 1 CVTWF 0 1 0 0 1 1 1 0 CVTLF 0 1 0 0 1 1 1 1 ACBF Supported in emul_branch ! 0 1 1 0 - - - - ---D- So let's decompose the opcode to find out what the operations are that we'll do, and we can overload this routine with all the operations. */ op = opcode-> function; dsize = ( op >> 5 ); /* 2 = F, 3 = D */ opcnt = ( op & 0x01 ) + 2; /* 2 or 3 */ func = ( op >> 1 ) & 0x07; /* 0 = ADD, 1 = SUB, 2 = MUL, 3 = DIV */ /* If the function is >= 4 then it's a conversion, remap them. */ /* func = 4 | 5 convert from float to integer */ /* func = 6 | 7 convert from integer to float */ if( func == 4 || func == 5 ) { func = 4; /* convert from float to integer */ dsize2 = op & 0x03; /* 0 = B, 1 = W, 2 = L, 3 = RL */ } else if( func == 6 || func == 7 ) { func = 5; /* convert from integer to float */ dsize2 = op & 0x03; /* 0 = B, 1 = W, 2 = L, 3 = RL */ if( op & 0x0F == 0x0F ) func = 6; /* Special case of ACBx */ } /* Handle conversions separately from math operations */ if( func == 4 ) { /* convert from float to integer */ /* Get the F_FLOAT operand */ d1 = *(( LONGWORD * ) src1 ); rc = fpu_load( d1, 0L, &float1 ); if( rc ) return rc; switch( dsize2 ) { case 0: /* Byte */ if( float1 < -128.0 || float1 > 127.0 ) { return set_fault( EXC_ARITH, 1, TRAP_INT_OVF ); } d1 = ( char ) float1; break; case 1: /* Word */ if( float1 < -65536.0 || float1 > 65535.0 ) { return set_fault( EXC_ARITH, 1, TRAP_INT_OVF ); } d1 = ( short ) float1; break; case 2: /* Long */ if( float1 < -128.0 || float1 > 127.0 ) { return set_fault( EXC_ARITH, 1, TRAP_INT_OVF ); } d1 = ( LONGWORD ) float1; break; default: set_fault( EXC_PRIV, 0 ); return VAX_FAULT; } SETCONDITIONBITS( d1, 0L ); return put_operand( opcode, opcode->count - 1, OP_WR, ( char * ) &d1 ); } if( func == 5 ) { /* convert from integer to float */ switch( dsize2 ) { case 0: /* Byte */ d1 = *(( char * ) src1 ); break; case 1: /* Word */ d1 = *(( short * ) src1 ); break; case 2: /* Long */ d1 = *(( LONGWORD * ) src1 ); break; default: set_fault( EXC_PRIV, 0 ); return VAX_FAULT; } SETCONDITIONBITS( d1, 0L ); float1 = d1; rc = fpu_store( float1, &d1, 0L /* F_FLOAT */ ); if( rc ) return rc; return put_operand( opcode, opcode->count - 1, OP_WR, ( char * ) &d1 ); } /* It's basic math. Based on data size, we must manipulate right-sized variables */ switch( dsize ) { case 2: /* F_FLOAT */ d1 = *(( LONGWORD * ) src1 ); d2 = *(( LONGWORD * ) src2 ); rc = fpu_load( d1, 0L, &float1 ); if( rc ) return rc; rc = fpu_load( d2, 0L, &float2 ); if( rc ) return rc; switch( func ) { case 0: float3 = float2 + float1; break; case 1: float3 = float2 - float1; break; case 2: float3 = float2 * float1; break; case 3: float3 = float2 / float1; break; } vax-> pslw.z = ( float3 == 0.0 ) ? 1 : 0; vax-> pslw.n = ( float3 < 0.0 ) ? 1 : 0; rc = fpu_store( float3, &data, 0L /* F_FLOAT */ ); if( rc ) vax-> pslw.v = 1; put_operand( opcode, opcode->count - 1, OP_WR, ( char * ) &data ); break; default: set_fault( EXC_PRIV, 0 ); return VAX_FAULT; } return VAX_OK; }