Lots of floating point, bugfixes, and system calls. Most of the tests pass now.
This commit is contained in:
David Given
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28
plat/linuxppc/emu/README.md
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28
plat/linuxppc/emu/README.md
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@ -0,0 +1,28 @@
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This is just a naive domestic PowerPC simulator, but I think you'll be amused
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by its presumption.
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The simulator implements just enough of the instruction set to make the tests
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pass. Certain features aren't supported at all (and an effort has been made
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to detect this and error out). The FPU is crudely approximated using the
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native floating-point support, doesn't support reading and writing FPSCR, and
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will almost certainly produce incorrect results. Plus, there are bugs. It's
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also likely to be very, very slow.
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However, it should be easily extensible and the emulator core is only about
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500 lines of code.
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Instructions are defined in `instructions.dat`; `mkdispatcher.lua` reads
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these in and generates the instruction decoder. `emu.c` contains the main
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emulator core. `main.c` contains the application front end and the incredibly
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crude syscall interface.
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TODO:
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- overflow bit support (instructions that try to set OV error out)
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- mtcrf
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- read string / write string
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- factor out the ELF loader, and linux68k/emu uses it too
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- floating point condition bits
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- bit-for-bit FPU emulation, although this looks like a huge amount of work
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It was written from scratch for the ACK by me, David Given.
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@ -4,6 +4,7 @@
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#include <stdbool.h>
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#include <strings.h>
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#include <byteswap.h>
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#include <math.h>
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#include "emu.h"
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#define BO4 (1<<0)
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@ -12,6 +13,10 @@
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#define BO1 (1<<3)
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#define BO0 (1<<4)
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#define XER_SO (1<<31)
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#define XER_OV (1<<30)
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#define XER_CA (1<<29)
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cpu_t cpu;
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static inline bool carry(void)
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@ -22,6 +27,16 @@ static inline bool carry(void)
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#define swb16(x) bswap_16(x)
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#define swb32(x) bswap_32(x)
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/* Returns the state of a carry flag after a three-way add. */
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static inline bool carry_3(uint32_t a, uint32_t b, uint32_t c)
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{
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if ((a+b) < a)
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return true;
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if ((a+b+c) < c)
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return true;
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return false;
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}
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static inline uint32_t reg(uint8_t n)
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{
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return cpu.gpr[n];
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@ -34,14 +49,33 @@ static inline uint32_t reg0(uint8_t n)
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return cpu.gpr[n];
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}
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static inline uint64_t tobytes(double n)
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/* Double to bytes */
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static inline uint64_t d2b(double n)
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{
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return *(uint64_t*)&n;
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}
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/* Float to bytes */
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static inline uint32_t f2b(float n)
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{
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return *(uint32_t*)&n;
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}
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/* Bytes to double */
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static inline double b2d(uint64_t n)
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{
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return *(double*)&n;
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}
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/* Bytes to float */
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static inline float b2f(uint32_t n)
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{
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return *(float*)&n;
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}
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static inline double fpr(uint8_t n)
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{
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return *(double*)&cpu.fpr[n];
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return b2d(cpu.fpr[n]);
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}
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static inline uint32_t ext8(int8_t n)
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@ -149,9 +183,16 @@ static void write_string(uint32_t address, uint8_t reg, uint8_t bytes)
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static uint32_t addo(uint32_t a, uint32_t b, uint32_t c, bool set_o, bool set_c)
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{
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if (set_o || set_c)
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fatal("can't use O or C bits in add yet");
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if (set_o)
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fatal("can't use O bit in add yet");
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if (set_c)
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{
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cpu.xer = cpu.xer & ~XER_CA;
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if (carry_3(a, b, c))
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cpu.xer = cpu.xer | XER_CA;
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}
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return a + b + c;
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}
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@ -201,6 +242,24 @@ static void compareu(uint32_t a, uint32_t b, uint8_t field)
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setcr(bit+3, cpu.xer & (1<<31));
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}
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static void comparef(double a, double b, uint8_t field)
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{
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uint8_t c;
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if (isnan(a) || isnan(b))
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c = 0x1;
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else if (a < b)
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c = 0x8;
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else if (a > b)
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c = 0x4;
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else
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c = 0x2;
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uint8_t bit = 28 - field*4; /* note PowerPC bit numbering */
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cpu.cr = cpu.cr & ~(0xf<<bit) | (c<<bit);
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/* TODO: ordered/unordered, FSPCR, etc. */
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}
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static uint32_t cntlzw(uint32_t source)
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{
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return 32 - ffs(source);
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@ -147,21 +147,65 @@
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<31--><RS->0<FXM--->.<144----->. mtcrf(FXM, reg(RS));
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<31--><RT->0.........<19------>. cpu.gpr[RT] = cpu.cr;
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# Floating point loads
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# Floating pointer operations follow.
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#
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# These are extremely crude, and just enough has been implemented to make the
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# tests pass. The FPSCR bits are all ignored completely.
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<50--><FRT><RA-><D------------>. cpu.fpr[FRT] = read_double(reg0(RA) + ext16(D));
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<31--><FRT><RA-><RB-><599----->. cpu.gpr[FRT] = read_double(reg0(RA) + reg(RB));
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<51--><FRT><RA-><D-------------> uint32_t ea = reg(RA) + ext16(D); cpu.fpr[FRT] = read_byte(ea); cpu.gpr[RA] = ea;
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<31--><FRT><RA-><RB-><631----->. uint32_t ea = reg(RA) + reg(RB); cpu.fpr[FRT] = read_long(ea); cpu.gpr[RA] = ea;
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# FPSCR manipulation
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# Floating point stores
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<63--><FRT>..........<583----->R fatal("mffs not supported");
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<63--><F>..<B>.......<64------>. fatal("mcrfs not supported");
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<63--><F>.......<U->.<134----->R fatal("mtsfsfi not supported");
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<63-->.<FLM--->.<FRB><711----->R fatal("mtfsf not supported");
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<63--><BT->..........<70------>R fatal("mtfsb0 not supported");
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<63--><BT->..........<38------>R fatal("mtfsb1 not supported");
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<54--><FRS><RA-><D------------>. write_double(read_double(reg0(RA) + ext16(D)), cpu.fpr[FRS]);
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# Floating point double loads (raw bits)
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<50--><FRT><RA-><D-------------> cpu.fpr[FRT] = read_double(reg0(RA) + ext16(D));
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<31--><FRT><RA-><RB-><599----->. cpu.fpr[FRT] = read_double(reg0(RA) + reg(RB));
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<51--><FRT><RA-><D-------------> uint32_t ea = reg(RA) + ext16(D); cpu.fpr[FRT] = read_double(ea); cpu.gpr[RA] = ea;
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<31--><FRT><RA-><RB-><631----->. uint32_t ea = reg(RA) + reg(RB); cpu.fpr[FRT] = read_double(ea); cpu.gpr[RA] = ea;
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# Floating point double stores (raw bits)
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<54--><FRS><RA-><D-------------> write_double(reg0(RA) + ext16(D), cpu.fpr[FRS]);
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<31--><FRS><RA-><RB-><727----->. write_double(reg0(RA) + reg(RB), cpu.fpr[FRS]);
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<55--><FRS><RA-><D-------------> uint32_t ea = reg(RA) + ext16(D); write_double(ea, cpu.fpr[FRS]); cpu.gpr[RA] = ea;
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<31--><FRS><RA-><RB-><759----->. uint32_t ea = reg(RA) + reg(RB); write_long(ea, cpu.fpr[FRS]); cpu.gpr[RA] = ea;
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<31--><FRS><RA-><RB-><759----->. uint32_t ea = reg(RA) + reg(RB); write_double(ea, cpu.fpr[FRS]); cpu.gpr[RA] = ea;
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# Floating point single loads (convert from single to double)
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<48--><FRT><RA-><D-------------> cpu.fpr[FRT] = d2b(b2f(read_long(reg0(RA) + ext16(D))));
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<31--><FRT><RA-><RB-><535----->. cpu.fpr[FRT] = d2b(b2f(read_long(reg0(RA) + reg(RB))));
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<49--><FRT><RA-><D-------------> uint32_t ea = reg(RA) + ext16(D); cpu.fpr[FRT] = d2b(b2f(read_long(ea))); cpu.gpr[RA] = ea;
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<31--><FRT><RA-><RB-><567----->. uint32_t ea = reg(RA) + reg(RB); cpu.fpr[FRT] = d2b(b2f(read_long(ea))); cpu.gpr[RA] = ea;
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# Floating point single stores (convert from double to single)
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<52--><FRS><RA-><D-------------> write_long(reg0(RA) + ext16(D), f2b(fpr(FRS)));
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<31--><FRS><RA-><RB-><663----->. write_long(reg0(RA) + reg(RB), f2b(fpr(FRS)));
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<53--><FRS><RA-><D-------------> uint32_t ea = reg(RA) + ext16(D); write_long(ea, f2b(fpr(FRS))); cpu.gpr[RA] = ea;
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<31--><FRS><RA-><RB-><695----->. uint32_t ea = reg(RA) + reg(RB); write_long(ea, f2b(fpr(FRS))); cpu.gpr[RA] = ea;
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# Floating point arithmetic
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<63--><FRT>.....<FRB><72------>R setcr1(R, cpu.fpr[FRT] = cpu.fpr[FRB]);
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<63--><FRT><FRA><FRB><20------>R setcr1(R, cpu.fpr[FRT] = tobytes(fpr(FRA) - fpr(FRB)));
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<63--><FRT>.....<FRB><40------>R setcr1(R, cpu.fpr[FRT] = d2b(-fpr(FRB)));
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<63--><FRT>.....<FRB><264----->R setcr1(R, cpu.fpr[FRT] = d2b(fabs(fpr(FRB))));
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<63--><FRT>.....<FRB><136----->R setcr1(R, cpu.fpr[FRT] = d2b(-fabs(fpr(FRB))));
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<63--><FRT><FRA><FRB><21------>R setcr1(R, cpu.fpr[FRT] = d2b(fpr(FRA) + fpr(FRB)));
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<63--><FRT><FRA><FRB><20------>R setcr1(R, cpu.fpr[FRT] = d2b(fpr(FRA) - fpr(FRB)));
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<63--><FRT><FRA><FRB><25------>R setcr1(R, cpu.fpr[FRT] = d2b(fpr(FRA) * fpr(FRB)));
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<63--><FRT><FRA><FRB><18------>R setcr1(R, cpu.fpr[FRT] = d2b(fpr(FRA) / fpr(FRB)));
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# Floating point comparisons
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<63--><F>..<FRA><FRB><0------->. comparef(fpr(FRA), fpr(FRB), F);
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<63--><F>..<FRA><FRB><32------>. comparef(fpr(FRA), fpr(FRB), F);
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# Floating point conversions
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<63--><FRT>.....<FRB><14------>R setcr1(R, fpr(FRB)); cpu.fpr[FRT] = (uint32_t)fpr(FRB);
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<63--><FRT>.....<FRB><15------>R setcr1(R, fpr(FRB)); cpu.fpr[FRT] = (uint32_t)fpr(FRB);
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@ -157,6 +157,11 @@ void system_call(uint8_t trapno)
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break;
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}
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case 20: /* getpid */
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case 48: /* signal */
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case 54: /* ioctl */
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case 67: /* sigaction */
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case 78: /* gettimeofday */
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case 126: /* sigprocmask */
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cpu.gpr[4] = 0;
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break;
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