[PATCH] D75326: [entry values] X86: Describe effects of MOV{8,16}ri (PR45053)

[David Stenberg via Phabricator via llvm-commits]

dstenb added inline comments.


================
Comment at: llvm/lib/Target/X86/X86InstrInfo.cpp:7795
     // 64-bit parameters, so we need to consider super-registers.
     if (!TRI->isSuperRegisterEq(MI.getOperand(0).getReg(), Reg))
       return None;
----------------
At least when I tried this out on a 8th generation i7, it seems that MOV8ri and MOV16ri do not modify the upper bits in super-registers.

```
        movl    $287454020, %edi        # imm = 0x11223344                                                                                                                                                                                                                                                                     
        mov     $21862, %di             # imm = 0x5566
        movb    $119, %dil              # imm = 0x77
        callq   call
```

That produces the value 0x11225577.

In this test case we try to describe:

```
    renamable $rsi = LEA64r $rip, 1, $noreg, @.str, $noreg, debug-location !51
    renamable $si = MOV16ri 2112
```

As `Reg` is a 32-bit register, I think we want to return something like this for the MOV16ri instruction:

```
ParamLoadedValue(Reg, (DW_OP_constu, 0xFFFF0000, DW_OP_and, DW_OP_constu, MI.getOperand(1).getImm(), DW_OP_or))
```




CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D75326/new/

https://reviews.llvm.org/D75326