Incorrect operand access mode for cmov

[dennisaa]

The listed operand access modes for cmov instructions in capstone/arch/X86/X86MappingInsnOp_reduce.inc look incorrect. They're listed as:

{ CS_AC_READ | CS_AC_WRITE, CS_AC_READ, 0 }

I would expect the access mode to be the same as for regular mov, i.e.:

{ CS_AC_WRITE, CS_AC_READ, 0 }

If this is not a bug, I would be interested in the reasoning behind marking cmov's destination operand as being read. As far as I know it can only be written (copied from the source operand) or left unchanged.

[keenk]

Sounds like the same issue as #1257
I never did go back and fix the rest in that file. Good to note that there are two files these need to be fixed in (_reduce and the non _reduce version).

[aquynh]

Please pull req

[keenk]

Ran into this myself and finally got around to putting in a pull request #1727

The destination operand of the conditional move (cmov...) instructions incorrectly states that they are READ | WRITE. These instructions actually do not read the destination operand at all, but instead rely on the associated flag set in EFLAGS.

Actual output from cstool for cmova eax, ecx (note READ | WRITE on operand[0]):
./cstool -d x32 "0f47c1"
0 0f 47 c1 cmova eax, ecx
ID: 80 (cmova)
Prefix:0x00 0x00 0x00 0x00
Opcode:0x0f 0x47 0x00 0x00
rex: 0x0
addr_size: 4
modrm: 0xc1
disp: 0x0
sib: 0x0
op_count: 2
operands[0].type: REG = eax
operands[0].size: 4
operands[0].access: READ | WRITE
operands[1].type: REG = ecx
operands[1].size: 4
operands[1].access: READ
Registers read: eflags eax ecx
Registers modified: eax
EFLAGS: TEST_ZF TEST_CF
Groups: cmov

Expected output from cstool (Note only WRITE on operand[0]):
./cstool -d x32 "0f47c1"
0 0f 47 c1 cmova eax, ecx
ID: 80 (cmova)
Prefix:0x00 0x00 0x00 0x00
Opcode:0x0f 0x47 0x00 0x00
rex: 0x0
addr_size: 4
modrm: 0xc1
disp: 0x0
sib: 0x0
op_count: 2
operands[0].type: REG = eax
operands[0].size: 4
operands[0].access: WRITE
operands[1].type: REG = ecx
operands[1].size: 4
operands[1].access: READ
Registers read: eflags ecx
Registers modified: eax
EFLAGS: TEST_ZF TEST_CF
Groups: cmov

The two files changed by this pull request indicate they are auto generated. I have had similar changes rolled back in the past (see #1512 ). If there is a better place to make these changes please let me know.