[X86] Avoid mangling frameescape labels

x86 Windows uses the '_' prefix for all global symbols, and this was
mistakenly being applied to frameescape labels, which are not externally
visible global symbols. They use the private global prefix 'L'.

The *right* way to fix this is probably to stop masquerading this label
as an ExternalSymbol and create a new SDNode type. These labels are not
"external", and we know they will be resolved by assembly time. Having a
custom SDNode type would allow us to do better X86 address mode
matching, so it's probably worth doing eventually.

llvm-svn: 236123

3 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h b/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h
index d4698bf492a..85b00068252 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h
@@ -213,7 +213,11 @@ namespace X86II {
     /// the offset from beginning of section.
     ///
     /// This is the TLS offset for the COFF/Windows TLS mechanism.
-    MO_SECREL
+    MO_SECREL,
+
+    /// MO_NOPREFIX - On a symbol operand this indicates that the symbol should
+    /// not be mangled with a prefix.
+    MO_NOPREFIX,
   };
 
   enum : uint64_t {
diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 0219430f812..fa71e3a599f 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1009,7 +1009,9 @@ bool X86DAGToDAGISel::MatchAddressRecursively(SDValue N, X86ISelAddressMode &AM,
     if (!AM.hasSymbolicDisplacement())
       if (const auto *ESNode = dyn_cast<ExternalSymbolSDNode>(N.getOperand(0)))
         if (ESNode->getOpcode() == ISD::TargetExternalSymbol) {
+          // Use the symbol and don't prefix it.
           AM.ES = ESNode->getSymbol();
+          AM.SymbolFlags = X86II::MO_NOPREFIX;
           return false;
         }
     break;
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 7eabff628ff..9ad03ae383b 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -154,7 +154,10 @@ GetSymbolFromOperand(const MachineOperand &MO) const {
     const GlobalValue *GV = MO.getGlobal();
     AsmPrinter.getNameWithPrefix(Name, GV);
   } else if (MO.isSymbol()) {
-    getMang()->getNameWithPrefix(Name, MO.getSymbolName());
+    if (MO.getTargetFlags() == X86II::MO_NOPREFIX)
+      Name += MO.getSymbolName();
+    else
+      getMang()->getNameWithPrefix(Name, MO.getSymbolName());
   } else if (MO.isMBB()) {
     Name += MO.getMBB()->getSymbol()->getName();
   }
@@ -231,6 +234,7 @@ MCOperand X86MCInstLower::LowerSymbolOperand(const MachineOperand &MO,
   case X86II::MO_DARWIN_NONLAZY:
   case X86II::MO_DLLIMPORT:
   case X86II::MO_DARWIN_STUB:
+  case X86II::MO_NOPREFIX:
     break;
 
   case X86II::MO_TLVP:      RefKind = MCSymbolRefExpr::VK_TLVP; break;