[llvm-bugs] [Bug 48877] New: [X86] Missing VEX_WIG from a bunch of AVX instruction definitions.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48877

            Bug ID: 48877
           Summary: [X86] Missing VEX_WIG from a bunch of AVX instruction
                    definitions.
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: andrea.dibiagio at gmail.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, pengfei.wang at intel.com,
                    spatel+llvm at rotateright.com

While testing the disassembler functionality using llvm-mc I found a few cases
where valid encodings were incorrectly reported as errors.

It turns out that all those problematic cases were related to instructions for
which the W bit from the VEX prefix is ignored.

---
Example 1.

VEX.NDS.128.66.0F38.WIG 2B /r
VPACKUSDW xmm1, xmm2, xmm3/m128


0xC4, 0xE2, 0xE9, 0x2B, 0x05, 0x15, 0x9D, 0x3F, 0x09  // NG
0xC4, 0xE2, 0x69, 0x2B, 0x05, 0x15, 0x9D, 0x3F, 0x09  // OK

The VEX.W is set in the NG case (byte #2 is 0xE9), and cleared in the OK case
(byte #2 is 0x69).

The definition is:
  defm VPACKUSDW : sse4_pack<0x2B, "vpackusdw", v8i16, v4i32, X86Packus, VR128,
                             i128mem, SchedWriteShuffle.XMM, load, 0>,
                             VEX_4V;

It is clearly missing a VEX_WIG.

---

Other problematic cases are which are affected by the same issue are:

VEX.NDS.128.66.0F38.WIG 06 /r
VPHSUBD xmm1, xmm2, xmm3/m128

0xC4, 0xE2, 0xE9, 0x06, 0x05, 0x24, 0x78, 0xF3, 0x07 // NG
0xC4, 0xE2, 0x69, 0x06, 0x05, 0x24, 0x78, 0xF3, 0x07 // OK

VEX.128.66.0F3A.WIG 61 /r ib
VPCMPESTRI xmm1, xmm2/m128, imm8

0xC4, 0xE3, 0xE9, 0x61, 0x05, 0x00, 0x25, 0x49, 0x02, 0x60  // OK
0xC4, 0xE3, 0xF9, 0x61, 0x05, 0x00, 0x25, 0x49, 0x02, 0x60  // NG

VPCMPESTRM xmm1, xmm2/m128, imm8
VPCMPISTRI xmm1, xmm2/m128, imm8
VPCMPISTRM xmm1, xmm2/m128, imm8

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