vendor/llvm/llvm-trunk-r242221

7 files changed, 120 insertions, 20 deletions

diff --git a/lib/Transforms/IPO/ArgumentPromotion.cpp b/lib/Transforms/IPO/ArgumentPromotion.cpp
index f75436328252..4762011d63d8 100644
--- a/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ b/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -825,7 +825,6 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
             V = GetElementPtrInst::Create(SI->first, V, Ops,
                                           V->getName() + ".idx", Call);
             Ops.clear();
-            AA.copyValue(OrigLoad->getOperand(0), V);
           }
           // Since we're replacing a load make sure we take the alignment
           // of the previous load.
@@ -837,7 +836,6 @@ CallGraphNode *ArgPromotion::DoPromotion(Function *F,
           newLoad->setAAMetadata(AAInfo);
 
           Args.push_back(newLoad);
-          AA.copyValue(OrigLoad, Args.back());
         }
       }
 
diff --git a/lib/Transforms/IPO/CMakeLists.txt b/lib/Transforms/IPO/CMakeLists.txt
index 3df17b920a95..336dac45e13a 100644
--- a/lib/Transforms/IPO/CMakeLists.txt
+++ b/lib/Transforms/IPO/CMakeLists.txt
@@ -3,6 +3,7 @@ add_llvm_library(LLVMipo
   BarrierNoopPass.cpp
   ConstantMerge.cpp
   DeadArgumentElimination.cpp
+  ElimAvailExtern.cpp
   ExtractGV.cpp
   FunctionAttrs.cpp
   GlobalDCE.cpp
diff --git a/lib/Transforms/IPO/DeadArgumentElimination.cpp b/lib/Transforms/IPO/DeadArgumentElimination.cpp
index 76898f275058..d0447640259e 100644
--- a/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -326,7 +326,18 @@ bool DAE::DeleteDeadVarargs(Function &Fn) {
 /// instead.
 bool DAE::RemoveDeadArgumentsFromCallers(Function &Fn)
 {
-  if (Fn.isDeclaration() || Fn.mayBeOverridden())
+  // We cannot change the arguments if this TU does not define the function or
+  // if the linker may choose a function body from another TU, even if the
+  // nominal linkage indicates that other copies of the function have the same
+  // semantics. In the below example, the dead load from %p may not have been
+  // eliminated from the linker-chosen copy of f, so replacing %p with undef
+  // in callers may introduce undefined behavior.
+  //
+  // define linkonce_odr void @f(i32* %p) {
+  //   %v = load i32 %p
+  //   ret void
+  // }
+  if (!Fn.isStrongDefinitionForLinker())
     return false;
 
   // Functions with local linkage should already have been handled, except the
@@ -334,19 +345,6 @@ bool DAE::RemoveDeadArgumentsFromCallers(Function &Fn)
   if (Fn.hasLocalLinkage() && !Fn.getFunctionType()->isVarArg())
     return false;
 
-  // If a function seen at compile time is not necessarily the one linked to
-  // the binary being built, it is illegal to change the actual arguments
-  // passed to it. These functions can be captured by isWeakForLinker().
-  // *NOTE* that mayBeOverridden() is insufficient for this purpose as it
-  // doesn't include linkage types like AvailableExternallyLinkage and
-  // LinkOnceODRLinkage. Take link_odr* as an example, it indicates a set of
-  // *EQUIVALENT* globals that can be merged at link-time. However, the
-  // semantic of *EQUIVALENT*-functions includes parameters. Changing
-  // parameters breaks this assumption.
-  //
-  if (Fn.isWeakForLinker())
-    return false;
-
   if (Fn.use_empty())
     return false;
 
diff --git a/lib/Transforms/IPO/ElimAvailExtern.cpp b/lib/Transforms/IPO/ElimAvailExtern.cpp
new file mode 100644
index 000000000000..67ba72d6a360
--- /dev/null
+++ b/lib/Transforms/IPO/ElimAvailExtern.cpp
@@ -0,0 +1,84 @@
+//===-- ElimAvailExtern.cpp - DCE unreachable internal functions ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This transform is designed to eliminate available external global
+// definitions from the program, turning them into declarations.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Transforms/Utils/CtorUtils.h"
+#include "llvm/Transforms/Utils/GlobalStatus.h"
+#include "llvm/Pass.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "elim-avail-extern"
+
+STATISTIC(NumFunctions, "Number of functions removed");
+STATISTIC(NumVariables, "Number of global variables removed");
+
+namespace {
+  struct EliminateAvailableExternally : public ModulePass {
+    static char ID; // Pass identification, replacement for typeid
+    EliminateAvailableExternally() : ModulePass(ID) {
+      initializeEliminateAvailableExternallyPass(
+          *PassRegistry::getPassRegistry());
+    }
+
+    // run - Do the EliminateAvailableExternally pass on the specified module,
+    // optionally updating the specified callgraph to reflect the changes.
+    //
+    bool runOnModule(Module &M) override;
+  };
+}
+
+char EliminateAvailableExternally::ID = 0;
+INITIALIZE_PASS(EliminateAvailableExternally, "elim-avail-extern",
+                "Eliminate Available Externally Globals", false, false)
+
+ModulePass *llvm::createEliminateAvailableExternallyPass() {
+  return new EliminateAvailableExternally();
+}
+
+bool EliminateAvailableExternally::runOnModule(Module &M) {
+  bool Changed = false;
+
+  // Drop initializers of available externally global variables.
+  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
+       I != E; ++I) {
+    if (!I->hasAvailableExternallyLinkage())
+      continue;
+    if (I->hasInitializer()) {
+      Constant *Init = I->getInitializer();
+      I->setInitializer(nullptr);
+      if (isSafeToDestroyConstant(Init))
+        Init->destroyConstant();
+    }
+    I->removeDeadConstantUsers();
+    I->setLinkage(GlobalValue::ExternalLinkage);
+    NumVariables++;
+  }
+
+  // Drop the bodies of available externally functions.
+  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
+    if (!I->hasAvailableExternallyLinkage())
+      continue;
+    if (!I->isDeclaration())
+      // This will set the linkage to external
+      I->deleteBody();
+    I->removeDeadConstantUsers();
+    NumFunctions++;
+  }
+
+  return Changed;
+}
diff --git a/lib/Transforms/IPO/ExtractGV.cpp b/lib/Transforms/IPO/ExtractGV.cpp
index 2f8c7d9349b9..b9462f2ffc72 100644
--- a/lib/Transforms/IPO/ExtractGV.cpp
+++ b/lib/Transforms/IPO/ExtractGV.cpp
@@ -93,8 +93,11 @@ namespace {
 
         makeVisible(*I, Delete);
 
-        if (Delete)
+        if (Delete) {
+          // Make this a declaration and drop it's comdat.
           I->setInitializer(nullptr);
+          I->setComdat(nullptr);
+        }
       }
 
       // Visit the Functions.
@@ -108,8 +111,11 @@ namespace {
 
         makeVisible(*I, Delete);
 
-        if (Delete)
+        if (Delete) {
+          // Make this a declaration and drop it's comdat.
           I->deleteBody();
+          I->setComdat(nullptr);
+        }
       }
 
       // Visit the Aliases.
diff --git a/lib/Transforms/IPO/IPO.cpp b/lib/Transforms/IPO/IPO.cpp
index fcacec3286fa..50f56b0f2afe 100644
--- a/lib/Transforms/IPO/IPO.cpp
+++ b/lib/Transforms/IPO/IPO.cpp
@@ -46,6 +46,7 @@ void llvm::initializeIPO(PassRegistry &Registry) {
   initializeStripDeadDebugInfoPass(Registry);
   initializeStripNonDebugSymbolsPass(Registry);
   initializeBarrierNoopPass(Registry);
+  initializeEliminateAvailableExternallyPass(Registry);
 }
 
 void LLVMInitializeIPO(LLVMPassRegistryRef R) {
diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 963f1bb13aaf..88e5e479136f 100644
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -105,6 +105,7 @@ PassManagerBuilder::PassManagerBuilder() {
     VerifyInput = false;
     VerifyOutput = false;
     MergeFunctions = false;
+    PrepareForLTO = false;
 }
 
 PassManagerBuilder::~PassManagerBuilder() {
@@ -319,8 +320,8 @@ void PassManagerBuilder::populateModulePassManager(
 
   // Re-rotate loops in all our loop nests. These may have fallout out of
   // rotated form due to GVN or other transformations, and the vectorizer relies
-  // on the rotated form.
-  MPM.add(createLoopRotatePass());
+  // on the rotated form. Disable header duplication at -Oz.
+  MPM.add(createLoopRotatePass(SizeLevel == 2 ? 0 : -1));
 
   // Distribute loops to allow partial vectorization.  I.e. isolate dependences
   // into separate loop that would otherwise inhibit vectorization.
@@ -401,6 +402,17 @@ void PassManagerBuilder::populateModulePassManager(
     // GlobalOpt already deletes dead functions and globals, at -O2 try a
     // late pass of GlobalDCE.  It is capable of deleting dead cycles.
     if (OptLevel > 1) {
+      if (!PrepareForLTO) {
+        // Remove avail extern fns and globals definitions if we aren't
+        // compiling an object file for later LTO. For LTO we want to preserve
+        // these so they are eligible for inlining at link-time. Note if they
+        // are unreferenced they will be removed by GlobalDCE below, so
+        // this only impacts referenced available externally globals.
+        // Eventually they will be suppressed during codegen, but eliminating
+        // here enables more opportunity for GlobalDCE as it may make
+        // globals referenced by available external functions dead.
+        MPM.add(createEliminateAvailableExternallyPass());
+      }
       MPM.add(createGlobalDCEPass());         // Remove dead fns and globals.
       MPM.add(createConstantMergePass());     // Merge dup global constants
     }