[X86][Disassembler] Fix displacement operand size for symbolizer

[maksfb]

Summary

On 64-bit X86, 0x66 operand-size override prefix will change the size of
the instruction operand, e.g. from 32 bits to 16 bits, but it will not
modify the size of the displacement operand used for memory addressing,
which will always be 32 bits.

[maksfb]

Friendly ping.

[rafauler]

LGTM

[skan]

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

505

Mov this statement to the scope of else if (insn->mode == MODE_64BIT) {?

llvm/unittests/MC/X86/X86MCDisassemblerTest.cpp

149

Could we use another register such as rbx as base register in this test? rip always use 32-bit displacement.

[maksfb]

Address comments.

[maksfb]

Adjust the operand value in the test case. The value should not be rip-adjusted.

[maksfb]

Rebase.

[maksfb]

Rebase.

[skan]

LGTM

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

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->displacementSize = 4;
       insn->immediateSize = (insn->hasOpSize ? 2 : 4);
     }
   }
 
   return 0;
 }
 
 // Consumes the SIB byte to determine addressing information.

llvm/unittests/MC/X86/X86MCDisassemblerTest.cpp

TEST(X86Disassembler, X86MCSymbolizerTest) {
   checkOperand(1, 0xffffffffffffefe8, 7, 4);
 
   // movq   $0xfffffffffffffef5, (%r12)
   // Test that the displacement operand has a size of 0, since it is not
   // explicitly specified in the instruction.
   checkBytes({0x49, 0xc7, 0x04, 0x24, 0xf5, 0xfe, 0xff, 0xff});
   checkOperand(0, 0, 4, 0);
   checkOperand(1, 0xfffffffffffffef5, 4, 4);
+
+  // mov    %ax, 0x1568179(%rip)
+  // Test that the displacement operand size is not affected by the operand
+  // size override prefix.
+  checkBytes({0x66, 0x89, 0x05, 0x79, 0x81, 0x56, 0x01});
+  checkOperand(0, 0x1568180, 3, 4);
 }