fix rdar://8456389 - llvm-mc mismatch with 'as' on 'fstp'

-This line, and those below, will be ignored--

M    test/MC/AsmParser/X86/x86_instructions.s
M    lib/Target/X86/AsmParser/X86AsmParser.cpp

llvm-svn: 114527

2 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
index 4c51ed674e3..d8650e06045 100644
--- a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -1015,6 +1015,14 @@ ParseInstruction(StringRef Name, SMLoc NameLoc,
     Operands[0] = X86Operand::CreateToken("movsl", NameLoc);
   }
   
+  // fstp <mem> -> fstps <mem>.  Without this, we'll default to fstpl due to
+  // suffix searching.
+  if (Name == "fstp" && Operands.size() == 2 &&
+      static_cast<X86Operand*>(Operands[1])->isMem()) {
+    delete Operands[0];
+    Operands[0] = X86Operand::CreateToken("fstps", NameLoc);
+  }
+  
   return false;
 }
 
diff --git a/llvm/test/MC/AsmParser/X86/x86_instructions.s b/llvm/test/MC/AsmParser/X86/x86_instructions.s
index 7f8a401c076..207de850e7d 100644
--- a/llvm/test/MC/AsmParser/X86/x86_instructions.s
+++ b/llvm/test/MC/AsmParser/X86/x86_instructions.s
@@ -310,3 +310,9 @@ enter $0x7ace,$0
 enter $0x7ace,$1
 enter $0x7ace,$0x7f
 
+
+// rdar://8456389
+// CHECK: fstps	(%eax)
+// CHECK: encoding: [0xd9,0x18]
+fstp	(%eax)
+