[X86] Fix disassembly of x86-64 GDTLS code sequence

[andrewng]

Summary

For x86-64 the REX.w prefix takes precedence over any other size
override (i.e. 0x66). Therefore, for x86-64 when REX.w is present set
'hasOpSize' to false to ensure that any size override is ignored.

Fixes PR48901.

[MaskRay]

LG

llvm/test/MC/Disassembler/X86/x86-64.txt

332–334

Add a TODO comment that this should display data16 prefixes.

llvm/test/tools/llvm-objdump/X86/disassemble-gdtls.s

2

llvm-mc %s -filetype=obj -triple=x86_64

This is not tied to Linux.

4

Add a TODO comment that this should display data16 prefixes.

[RKSimon]

llvm/test/tools/llvm-objdump/X86/disassemble-gdtls.s

9

Please can you rename 'foo' to 'PR48901' - it greatly speeds up tracking back through tests if we know which bug it came from.

[andrewng]

Updated to address review comments.

[MaskRay]

Thanks! I'd let @RKSimon sign off as well.

[MaskRay]

llvm/test/MC/Disassembler/X86/x86-64.txt

332

This perhaps needs a CHECK-NOT: data16 to enforce this.

[RKSimon]

LGTM - cheers

llvm/lib/Target/X86/Disassembler/X86Disassembler.cpp

if (insn->mode == MODE_16BIT) {
     insn->displacementSize = (insn->hasAdSize ? 2 : 4);
     insn->immediateSize = (insn->hasOpSize ? 2 : 4);
   } else if (insn->mode == MODE_64BIT) {
     if (insn->rexPrefix && wFromREX(insn->rexPrefix)) {
       insn->registerSize = 8;
       insn->addressSize = (insn->hasAdSize ? 4 : 8);
       insn->displacementSize = 4;
       insn->immediateSize = 4;
+      insn->hasOpSize = false;
     } else {
       insn->registerSize = (insn->hasOpSize ? 2 : 4);
       insn->addressSize = (insn->hasAdSize ? 4 : 8);
       insn->displacementSize = (insn->hasOpSize ? 2 : 4);
       insn->immediateSize = (insn->hasOpSize ? 2 : 4);
     }
   }
 

llvm/test/MC/Disassembler/X86/x86-64.txt

 0x48 0xa3 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a
 
 # CHECK: movq %rax, 1515870810
 0x67, 0x48 0xa3 0x5a 0x5a 0x5a 0x5a
 
 # CHECK: callw 32767
 0x66 0xe8 0xff 0x7f
 
-# CHECK: callw 32767
-0x66 0x66 0x48 0xe8 0xff 0x7f
+# TODO: Should display data16 prefixes.
+# CHECK: callq 32767
+0x66 0x66 0x48 0xe8 0xff 0x7f 0x00 0x00
 
 # CHECK: jmp -32769
 0xe9 0xff 0x7f 0xff 0xff
 
 # CHECK: jmp 32767
 0x66 0xe9 0xff 0x7f
 
+# TODO: Should display data16 prefixes.
 # CHECK: jmp 32767
-0x66 0x66 0x48 0xe9 0xff 0x7f
+0x66 0x66 0x48 0xe9 0xff 0x7f 0x00 0x00
 
 # CHECK: jo -32769
 0x0f 0x80 0xff 0x7f 0xff 0xff
 
 # CHECK: jo 32767
 0x66 0x0f 0x80 0xff 0x7f
 
 # CHECK: jno -32769

llvm/test/tools/llvm-objdump/X86/disassemble-gdtls.s

+# RUN: llvm-mc %s -filetype=obj -triple=x86_64 | llvm-objdump -d - | FileCheck %s
+
+# CHECK:      <PR48901>:
+# TODO: Should display data16 prefixes.
+# CHECK-NEXT: 0: 66 48 8d 3d 00 00 00 00       leaq    (%rip), %rdi  # 8 <PR48901+0x8>
+# CHECK-NEXT: 8: 66 66 48 e8 00 00 00 00       callq   0x10 <PR48901+0x10>
+# CHECK-EMPTY:
+
+PR48901:
+ data16
+ leaq   bar@TLSGD(%rip),%rdi
+ data16
+ data16
+ rex64
+ callq  __tls_get_addr@PLT
+
+.section .tdata,"awT",@progbits
+bar:
+.long 42