[x86 disassembler] Certain VEX instructions ignore the W-bit that shouldn't

[topperc]

Bugzilla Link	11304
Resolution	FIXED
Resolved on	Nov 07, 2017 03:34
Version	trunk
OS	All
Blocks	#11360

Extended Description

All of the instructions that are specified in the Intel developer manuals with W0 and have no corresponding W1 form will still disassemble with VEX.W=1.

Examples:
VEXTRACTF128
VINSERTF128
VPERMILPD
VPERMILPS
VPERM2F128
VBROADCAST*
VTESTPD
VTESTPS

[llvmbot]

Craig,
Do you like to see error message here or warning will be enough?

[llvmbot]

BTW, the similar situation we have when #UD If (VEX.L = 1 && AVX2 not present && AVX present). I suppose it should be fixed as well, right?

[topperc]

I'd prefer an error message I think. What does the gnu assembler do?

Not sure I understood the question about #UD. The disassembler has no idea what features are enabled or not on the code its disassembling. The only information it has is whether we are in 16, 32, or 64 bit mode.

[llvmbot]

Intel Vol 2.a, 2.4 AVX AND SSE INSTRUCTION EXCEPTION SPECIFICATION has tables describing #UD producing by some instructions, e.g. "#UD If VEX.W = 1 in all modes" or "#UD If VEX.L = 0". I suppose disassembler should produce error messages for all those instructions under given conditions, right?

[topperc]

The disassembler shouldn't really know what features are enabled. It needs to work in tools like llvm-objdump where the only information we have is 32-bit mode vs 64-bit mode as indicated by the ELF header. There's no information in a binary that says what features were enabled. And you don't want the user to have to provide such information themselves.

[llvmbot]

OK, in this case we should produce errors for "#UD If VEX.W = 1 in all modes" only, right?

BTW could you review D38626 and D38786 (they both are rather small and should not take real time.)

[topperc]

Fixed in r316285

[llvmbot]

*** Bug llvm/llvm-bugzilla-archive#32804 has been marked as a duplicate of this bug. ***

[llvmbot]

mentioned in issue llvm/llvm-bugzilla-archive#32804