From: David Woodhouse <dwmw2@infradead.org>
Date: Wed, 8 Jan 2014 12:58:12 +0000 (+0000)
Subject: [x86] Fix JCXZ,JECXZ_32 for 16-bit mode
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=975fe2cfc34c605746a644e96ff2cb96a7855131;p=oota-llvm.git

[x86] Fix JCXZ,JECXZ_32 for 16-bit mode

JCXZ should have the 0x67 prefix only if we're in 32-bit mode, so make that
appropriately conditional. And JECXZ needs the prefix instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198757 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
index e44574c31e2..d3879e6c4cf 100644
--- a/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ b/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -1161,7 +1161,11 @@ void X86MCCodeEmitter::EmitOpcodePrefix(uint64_t TSFlags, unsigned &CurByte,
 
   // Emit the address size opcode prefix as needed.
   bool need_address_override;
-  if (TSFlags & X86II::AdSize) {
+  // The AdSize prefix is only for 32-bit and 64-bit modes; in 16-bit mode we
+  // need the address override only for JECXZ instead. Since it's only one
+  // instruction, we special-case it rather than introducing an AdSize16 bit.
+  if ((!is16BitMode() && TSFlags & X86II::AdSize) ||
+      (is16BitMode() && MI.getOpcode() == X86::JECXZ_32)) {
     need_address_override = true;
   } else if (MemOperand == -1) {
     need_address_override = false;
diff --git a/test/MC/X86/x86-16.s b/test/MC/X86/x86-16.s
index 9fdd8645e7a..e395a779f23 100644
--- a/test/MC/X86/x86-16.s
+++ b/test/MC/X86/x86-16.s
@@ -356,6 +356,14 @@ cmovnae	%bx,%bx
 lcalll $0x2, $0x1234
 
 
+L1:
+  jcxz L1
+// CHECK: jcxz L1
+// CHECK:   encoding: [0xe3,A]
+  jecxz L1
+// CHECK: jecxz L1
+// CHECK:   encoding: [0x67,0xe3,A]
+
 iret
 // CHECK: iretw
 // CHECK: encoding: [0xcf]