Update llvm/clang to trunk r126547.

There are several bugfixes in this update, but the most important one is
to ensure __start_ and __stop_ symbols for linker sets and kernel module
metadata are always emitted in object files:

  http://llvm.org/bugs/show_bug.cgi?id=9292

Before this fix, if you compiled kernel modules with clang, they would
not be properly processed by kldxref, and if they had any dependencies,
the kernel would fail to load those.  Another problem occurred when
attempting to mount a tmpfs filesystem, which would result in 'operation
not supported by device'.

1 files changed, 57 insertions, 25 deletions

diff --git a/contrib/llvm/tools/clang/lib/CodeGen/CGExpr.cpp b/contrib/llvm/tools/clang/lib/CodeGen/CGExpr.cpp
index 1b7e7a0..2abaadf 100644
--- a/contrib/llvm/tools/clang/lib/CodeGen/CGExpr.cpp
+++ b/contrib/llvm/tools/clang/lib/CodeGen/CGExpr.cpp
@@ -260,6 +260,10 @@ EmitExprForReferenceBinding(CodeGenFunction &CGF, const Expr *E,
         }
       }
 
+      if (const OpaqueValueExpr *opaque = dyn_cast<OpaqueValueExpr>(E))
+        if (opaque->getType()->isRecordType())
+          return CGF.EmitOpaqueValueLValue(opaque).getAddress();
+
       // Nothing changed.
       break;
     }
@@ -1606,39 +1610,67 @@ LValue CodeGenFunction::EmitLValueForAnonRecordField(llvm::Value *BaseValue,
   }
 }
 
-LValue CodeGenFunction::EmitLValueForField(llvm::Value *BaseValue,
-                                           const FieldDecl *Field,
-                                           unsigned CVRQualifiers) {
-  if (Field->isBitField())
-    return EmitLValueForBitfield(BaseValue, Field, CVRQualifiers);
+LValue CodeGenFunction::EmitLValueForField(llvm::Value *baseAddr,
+                                           const FieldDecl *field,
+                                           unsigned cvr) {
+  if (field->isBitField())
+    return EmitLValueForBitfield(baseAddr, field, cvr);
 
-  const CGRecordLayout &RL =
-    CGM.getTypes().getCGRecordLayout(Field->getParent());
-  unsigned idx = RL.getLLVMFieldNo(Field);
-  llvm::Value *V = Builder.CreateStructGEP(BaseValue, idx, "tmp");
+  const RecordDecl *rec = field->getParent();
+  QualType type = field->getType();
+
+  bool mayAlias = rec->hasAttr<MayAliasAttr>();
 
-  // Match union field type.
-  if (Field->getParent()->isUnion()) {
-    const llvm::Type *FieldTy =
-      CGM.getTypes().ConvertTypeForMem(Field->getType());
-    const llvm::PointerType *BaseTy =
-      cast<llvm::PointerType>(BaseValue->getType());
-    unsigned AS = BaseTy->getAddressSpace();
-    V = Builder.CreateBitCast(V,
-                              llvm::PointerType::get(FieldTy, AS),
-                              "tmp");
+  llvm::Value *addr;
+  if (rec->isUnion()) {
+    // For unions, we just cast to the appropriate type.
+    assert(!type->isReferenceType() && "union has reference member");
+
+    const llvm::Type *llvmType = CGM.getTypes().ConvertTypeForMem(type);
+    unsigned AS =
+      cast<llvm::PointerType>(baseAddr->getType())->getAddressSpace();
+    addr = Builder.CreateBitCast(baseAddr, llvmType->getPointerTo(AS),
+                                 field->getName());
+  } else {
+    // For structs, we GEP to the field that the record layout suggests.
+    unsigned idx = CGM.getTypes().getCGRecordLayout(rec).getLLVMFieldNo(field);
+    addr = Builder.CreateStructGEP(baseAddr, idx, field->getName());
+
+    // If this is a reference field, load the reference right now.
+    if (const ReferenceType *refType = type->getAs<ReferenceType>()) {
+      llvm::LoadInst *load = Builder.CreateLoad(addr, "ref");
+      if (cvr & Qualifiers::Volatile) load->setVolatile(true);
+
+      if (CGM.shouldUseTBAA()) {
+        llvm::MDNode *tbaa;
+        if (mayAlias)
+          tbaa = CGM.getTBAAInfo(getContext().CharTy);
+        else
+          tbaa = CGM.getTBAAInfo(type);
+        CGM.DecorateInstruction(load, tbaa);
+      }
+
+      addr = load;
+      mayAlias = false;
+      type = refType->getPointeeType();
+      cvr = 0; // qualifiers don't recursively apply to referencee
+    }
   }
-  if (Field->getType()->isReferenceType())
-    V = Builder.CreateLoad(V, "tmp");
 
-  unsigned Alignment = getContext().getDeclAlign(Field).getQuantity();
-  LValue LV = MakeAddrLValue(V, Field->getType(), Alignment);
-  LV.getQuals().addCVRQualifiers(CVRQualifiers);
+  unsigned alignment = getContext().getDeclAlign(field).getQuantity();
+  LValue LV = MakeAddrLValue(addr, type, alignment);
+  LV.getQuals().addCVRQualifiers(cvr);
 
   // __weak attribute on a field is ignored.
   if (LV.getQuals().getObjCGCAttr() == Qualifiers::Weak)
     LV.getQuals().removeObjCGCAttr();
-  
+
+  // Fields of may_alias structs act like 'char' for TBAA purposes.
+  // FIXME: this should get propagated down through anonymous structs
+  // and unions.
+  if (mayAlias && LV.getTBAAInfo())
+    LV.setTBAAInfo(CGM.getTBAAInfo(getContext().CharTy));
+
   return LV;
 }