diff options
Diffstat (limited to '023float.cc')
| -rw-r--r-- | 023float.cc | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/023float.cc b/023float.cc index cbd1bc80..324ab934 100644 --- a/023float.cc +++ b/023float.cc @@ -375,3 +375,42 @@ float* effective_address_float(uint8_t modrm) { trace(Callstack_depth+1, "run") << "effective address contains " << read_mem_f32(addr) << end(); return mem_addr_f32(addr); } + +//: compare + +:(before "End Initialize Op Names") +put_new(Name_0f, "2f", "compare: set SF if x32 < xm32 (comiss)"); + +:(code) +void test_compare_x32_with_mem_at_rm32() { + Reg[EAX].i = 0x2000; + Xmm[3] = 0.5; + run( + "== code 0x1\n" + // op ModR/M SIB displacement immediate + " 0f 2f 18 \n" // compare XMM3 with *EAX + // ModR/M in binary: 00 (indirect mode) 011 (lhs XMM3) 000 (rhs EAX) + "== data 0x2000\n" + "00 00 00 00\n" // 0x00000000 = 0.0 + ); + CHECK_TRACE_CONTENTS( + "run: compare XMM3 with x/m32\n" + "run: effective address is 0x00002000 (EAX)\n" + "run: SF=0; ZF=0; CF=0; OF=0\n" + ); +} + +:(before "End Two-Byte Opcodes Starting With 0f") +case 0x2f: { // set SF if x32 < x/m32 + const uint8_t modrm = next(); + const uint8_t reg1 = (modrm>>3)&0x7; + trace(Callstack_depth+1, "run") << "compare " << Xname[reg1] << " with x/m32" << end(); + const float* arg2 = effective_address_float(modrm); + // Flag settings carefully copied from the Intel manual. + // See also https://stackoverflow.com/questions/7057501/x86-assembler-floating-point-compare/7057771#7057771 + SF = ZF = CF = OF = false; + if (Xmm[reg1] == *arg2) ZF = true; + if (Xmm[reg1] < *arg2) CF = true; + trace(Callstack_depth+1, "run") << "SF=" << SF << "; ZF=" << ZF << "; CF=" << CF << "; OF=" << OF << end(); + break; +} |