[llvm] [BOLT] Avoid reference updates for non-JT symbol operands (PR #88838)

[via llvm-commits]

linsinan1995 wrote:

pass validate-memrefs wrongly update the correct reference to the jump table reference, which leads to a different execution result.

(a.out is compiled from jt-symbol-disambiguation-4.s attached in this PR)
```
+ ./a.out
FF
+ ./llvm-bolt -v=2 -jump-tables=move a.out -o a.out-opt
+ ./a.out-opt
5FFC00E
+ ./llvm-bolt -v=2 a.out -o a.out-opt-nomove
+ ./a.out-opt-nomove
FF
```

a.out
```
0000000000401160 <foo>:
  401160:       48 c7 c0 00 00 00 00    mov    $0x0,%rax
  401167:       ff 24 c5 18 20 40 00    jmpq   *0x402018(,%rax,8) // JT label address 0x402018
                        40116a: R_X86_64_32S    .rodata+0x18
  ...

0000000000401130 <main>:
  401130:       48 c7 c0 f0 ff ff ff    mov    $0xfffffffffffffff0,%rax
  401137:       8b 90 19 20 40 00       mov    0x402019(%rax),%edx // var `c` address 0x402008
                        401139: R_X86_64_32S    c+0x11
  40113d:       89 d6                   mov    %edx,%esi

0000000000402008 <c>:
  402008:       01 ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00     ................
  402018:       71 11 40 00 00 00 00 00 71 11 40 00 00 00 00 00     q. at .....q.@.....
  ...
```

a.out-opt
```
0000000000800122 <foo>:
  800122:       48 c7 c0 00 00 00 00    mov    $0x0,%rax
  800129:       ff 24 c5 20 03 80 00    jmpq   *0x800320(,%rax,8) # JT label address 0x800320
  ...

0000000000800100 <main>:
  800100:       48 c7 c0 f0 ff ff ff    mov    $0xfffffffffffffff0,%rax
  800107:       8b 90 21 03 80 00       mov    0x800321(%rax),%edx
  80010d:       89 d6                   mov    %edx,%esi

0000000000800320 <.rodata.cold>:
  800320:       30 01                   xor    %al,(%rcx)
  800322:       80 00 00              addb   $0x0,(%rax)
  800325:       00 00                   add    %al,(%rax)
  800327:       00 30                   add    %dh,(%rax)
```


`main` before validate-memref from BOLT log
```
.LBB07 (8 instructions, align : 1)
  Entry Point
  CFI State : 0
    00000000: 	movq	$-0x10, %rax
    00000007: 	movl	c+17(%rax), %edx
    0000000d: 	movl	%edx, %esi
    0000000f: 	movl	$SYMBOLat0x402038, %edi
    00000014: 	movl	$0x0, %eax
    00000019: 	callq	printf at PLT
    0000001e: 	xorl	%eax, %eax
    00000020: 	retq
  CFI State: 0
```

`main`  after validate-memref from BOLT log
```
.LBB07 (8 instructions, align : 1)
  Entry Point
  CFI State : 0
    00000000: 	movq	$-0x10, %rax
    00000007: 	movl	"JUMP_TABLE/foo/1.0"+1(%rax), %edx
    0000000d: 	movl	%edx, %esi
    0000000f: 	movl	$SYMBOLat0x402038, %edi
    00000014: 	movl	$0x0, %eax
    00000019: 	callq	printf at PLT
    0000001e: 	xorl	%eax, %eax
    00000020: 	retq
  CFI State: 0
```

https://github.com/llvm/llvm-project/pull/88838