[X86] Incorrect shuffle comment decoding for `vinsertps`

[omern1]

Reproducer

; input.s
.intel_syntax
vinsertps xmm2,xmm2,dword ptr [r14+rdi*8+0x4C],0x0B0

Current behaviour

> llvm-mc -triple x86_64-unknown-unknown input.s

.text
vinsertps       $176, 76(%r14,%rdi,8), %xmm2, %xmm2 # xmm2 = xmm2[0,1,2],mem[2]

Note that shuffle comment says mem[2]. The part describing vinsertps operation in the Intel SDM says the following:

IF (SRC = REG) THEN COUNT_S := imm8[7:6] ELSE COUNT_S := 0

In input.s the source for the vinsertps is not a register therefore the source index in the comment should be 0 (mem[0]).

[llvmbot]

@llvm/issue-subscribers-backend-x86

Author: Nabeel Omer (omern1)

### Reproducer ``` ; input.s .intel_syntax vinsertps xmm2,xmm2,dword ptr [r14+rdi*8+0x4C],0x0B0 ``` ### Current behaviour ``` > llvm-mc -triple x86_64-unknown-unknown input.s

.text
vinsertps $176, 76(%r14,%rdi,8), %xmm2, %xmm2 # xmm2 = xmm2[0,1,2],mem[2]

Note that shuffle comment says `mem[2]`. The part describing vinsertps operation in the Intel SDM says the following:

IF (SRC = REG) THEN COUNT_S := imm8[7:6] ELSE COUNT_S := 0

In input.s the source for the vinsertps is not a register therefore the source index in the comment should be 0 (`mem[0]`).


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