vendor/llvm/llvm-trunk-r321017

1 files changed, 29 insertions, 10 deletions

diff --git a/lib/Target/TargetMachine.cpp b/lib/Target/TargetMachine.cpp
index e8fe0a2b218ee..ad63c7a9cb304 100644
--- a/lib/Target/TargetMachine.cpp
+++ b/lib/Target/TargetMachine.cpp
@@ -13,7 +13,8 @@
 
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
-#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/TargetLoweringObjectFile.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalValue.h"
@@ -26,15 +27,8 @@
 #include "llvm/MC/MCSectionMachO.h"
 #include "llvm/MC/MCTargetOptions.h"
 #include "llvm/MC/SectionKind.h"
-#include "llvm/Target/TargetLowering.h"
-#include "llvm/Target/TargetLoweringObjectFile.h"
-#include "llvm/Target/TargetSubtargetInfo.h"
 using namespace llvm;
 
-cl::opt<bool> EnableIPRA("enable-ipra", cl::init(false), cl::Hidden,
-                         cl::desc("Enable interprocedural register allocation "
-                                  "to reduce load/store at procedure calls."));
-
 //---------------------------------------------------------------------------
 // TargetMachine Class
 //
@@ -45,8 +39,6 @@ TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
     : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
       TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
       RequireStructuredCFG(false), DefaultOptions(Options), Options(Options) {
-  if (EnableIPRA.getNumOccurrences())
-    this->Options.EnableIPRA = EnableIPRA;
 }
 
 TargetMachine::~TargetMachine() {
@@ -120,6 +112,17 @@ static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
 
 bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
                                          const GlobalValue *GV) const {
+  // If the IR producer requested that this GV be treated as dso local, obey.
+  if (GV && GV->isDSOLocal())
+    return true;
+
+  // According to the llvm language reference, we should be able to just return
+  // false in here if we have a GV, as we know it is dso_preemptable.
+  // At this point in time, the various IR producers have not been transitioned
+  // to always produce a dso_local when it is possible to do so. As a result we
+  // still have some pre-dso_local logic in here to improve the quality of the
+  // generated code:
+
   Reloc::Model RM = getRelocationModel();
   const Triple &TT = getTargetTriple();
 
@@ -134,6 +137,15 @@ bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
   if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))
     return true;
 
+  // Most PIC code sequences that assume that a symbol is local cannot
+  // produce a 0 if it turns out the symbol is undefined. While this
+  // is ABI and relocation depended, it seems worth it to handle it
+  // here.
+  // FIXME: this is probably not ELF specific.
+  if (GV && isPositionIndependent() && TT.isOSBinFormatELF() &&
+      GV->hasExternalWeakLinkage())
+    return false;
+
   if (GV && (GV->hasLocalLinkage() || !GV->hasDefaultVisibility()))
     return true;
 
@@ -153,6 +165,13 @@ bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
     if (GV && !GV->isDeclarationForLinker())
       return true;
 
+    // A symbol marked nonlazybind should not be accessed with a plt. If the
+    // symbol turns out to be external, the linker will convert a direct
+    // access to an access via the plt, so don't assume it is local.
+    const Function *F = dyn_cast_or_null<Function>(GV);
+    if (F && F->hasFnAttribute(Attribute::NonLazyBind))
+      return false;
+
     bool IsTLS = GV && GV->isThreadLocal();
     bool IsAccessViaCopyRelocs =
         Options.MCOptions.MCPIECopyRelocations && GV && isa<GlobalVariable>(GV);