From c69547136582e1e3155c903202583aea6490faf0 Mon Sep 17 00:00:00 2001
From: Reid Kleckner <reid@kleckner.net>
Date: Wed, 29 Apr 2015 16:46:01 +0000
Subject: [PATCH] [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
---
 llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h | 6 +++++-
 llvm/lib/Target/X86/X86ISelDAGToDAG.cpp        | 2 ++
 llvm/lib/Target/X86/X86MCInstLower.cpp         | 6 +++++-
 llvm/test/CodeGen/X86/frameescape.ll           | 6 +++---
 4 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h b/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h
index d4698bf492ad..85b00068252d 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 0219430f812a..fa71e3a599f5 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 7eabff628ff8..9ad03ae383be 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;
diff --git a/llvm/test/CodeGen/X86/frameescape.ll b/llvm/test/CodeGen/X86/frameescape.ll
index 3a624ae863de..098b6162e821 100644
--- a/llvm/test/CodeGen/X86/frameescape.ll
+++ b/llvm/test/CodeGen/X86/frameescape.ll
@@ -37,15 +37,15 @@ define void @print_framealloc_from_fp(i8* %fp) {
 ; X86: pushl   %esi
 ; X86: subl    $8, %esp
 ; X86: movl    16(%esp), %esi
-; X86: movl    _Lalloc_func$frame_escape_0(%esi), %eax
+; X86: movl    Lalloc_func$frame_escape_0(%esi), %eax
 ; X86: movl    %eax, 4(%esp)
 ; X86: movl    $_str, (%esp)
 ; X86: calll   _printf
-; X86: movl    _Lalloc_func$frame_escape_1(%esi), %eax
+; X86: movl    Lalloc_func$frame_escape_1(%esi), %eax
 ; X86: movl    %eax, 4(%esp)
 ; X86: movl    $_str, (%esp)
 ; X86: calll   _printf
-; X86: movl    $42, _Lalloc_func$frame_escape_1(%esi)
+; X86: movl    $42, Lalloc_func$frame_escape_1(%esi)
 ; X86: addl    $8, %esp
 ; X86: popl    %esi
 ; X86: retl