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| author | Kartik K. Agaram <vc@akkartik.com> | 2017-10-14 22:53:18 -0700 |
|---|---|---|
| committer | Kartik K. Agaram <vc@akkartik.com> | 2017-10-14 23:00:05 -0700 |
| commit | c67ca4b92674620f3cae3b9301471e0321a7936c (patch) | |
| tree | fb471c4ae56d38f6731d913b1450eec025ae7351 /subx/011direct_addressing.cc | |
| parent | 0cb3c774b207c8a94bf9f9775e99e7d593d1e4fe (diff) | |
| download | mu-c67ca4b92674620f3cae3b9301471e0321a7936c.tar.gz | |
4065
subx: 'compare' Hopefully I've implemented the 'sense' of comparisons right..
Diffstat (limited to 'subx/011direct_addressing.cc')
| -rw-r--r-- | subx/011direct_addressing.cc | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/subx/011direct_addressing.cc b/subx/011direct_addressing.cc index a1d83b8c..facc8378 100644 --- a/subx/011direct_addressing.cc +++ b/subx/011direct_addressing.cc @@ -148,3 +148,48 @@ case 0xf7: { // xor r32 with r/m32 OF = false; break; } + +//:: compare + +:(scenario compare_r32_with_r32_greater) +% Reg[0].i = 0x0a0b0c0d; +% Reg[3].i = 0x0a0b0c07; +# op ModRM SIB displacement immediate + 39 d8 # compare EBX (reg 3) with EAX (reg 0) ++run: compare reg 3 with effective address ++run: effective address is reg 0 ++run: SF=0; ZF=0; OF=0 + +:(before "End Single-Byte Opcodes") +case 0x39: { // compare r32 with r/m32 + uint8_t modrm = next(); + uint8_t reg2 = (modrm>>3)&0x7; + trace(2, "run") << "compare reg " << NUM(reg2) << " with effective address" << end(); + int32_t* arg1 = effective_address(modrm); + int32_t arg2 = Reg[reg2].i; + int32_t tmp1 = *arg1 - arg2; + SF = (tmp1 < 0); + ZF = (tmp1 == 0); + int64_t tmp2 = *arg1 - arg2; + OF = (tmp1 != tmp2); + trace(2, "run") << "SF=" << SF << "; ZF=" << ZF << "; OF=" << OF << end(); + break; +} + +:(scenario compare_r32_with_r32_lesser) +% Reg[0].i = 0x0a0b0c07; +% Reg[3].i = 0x0a0b0c0d; +# op ModRM SIB displacement immediate + 39 d8 # compare EBX (reg 3) with EAX (reg 0) ++run: compare reg 3 with effective address ++run: effective address is reg 0 ++run: SF=1; ZF=0; OF=0 + +:(scenario compare_r32_with_r32_equal) +% Reg[0].i = 0x0a0b0c0d; +% Reg[3].i = 0x0a0b0c0d; +# op ModRM SIB displacement immediate + 39 d8 # compare EBX (reg 3) with EAX (reg 0) ++run: compare reg 3 with effective address ++run: effective address is reg 0 ++run: SF=0; ZF=1; OF=0 |