MFC 261991:

Upgrade our copy of llvm/clang to 3.4 release.  This version supports
all of the features in the current working draft of the upcoming C++
standard, provisionally named C++1y.

The code generator's performance is greatly increased, and the loop
auto-vectorizer is now enabled at -Os and -O2 in addition to -O3.  The
PowerPC backend has made several major improvements to code generation
quality and compile time, and the X86, SPARC, ARM32, Aarch64 and SystemZ
backends have all seen major feature work.

Release notes for llvm and clang can be found here:
<http://llvm.org/releases/3.4/docs/ReleaseNotes.html>
<http://llvm.org/releases/3.4/tools/clang/docs/ReleaseNotes.html>

MFC 262121 (by emaste):

Update lldb for clang/llvm 3.4 import

This commit largely restores the lldb source to the upstream r196259
snapshot with the addition of threaded inferior support and a few bug
fixes.

Specific upstream lldb revisions restored include:
   SVN      git
  181387  779e6ac
  181703  7bef4e2
  182099  b31044e
  182650  f2dcf35
  182683  0d91b80
  183862  15c1774
  183929  99447a6
  184177  0b2934b
  184948  4dc3761
  184954  007e7bc
  186990  eebd175

Sponsored by:	DARPA, AFRL

MFC 262186 (by emaste):

Fix mismerge in r262121

A break statement was lost in the merge.  The error had no functional
impact, but restore it to reduce the diff against upstream.

MFC 262303:

Pull in r197521 from upstream clang trunk (by rdivacky):

  Use the integrated assembler by default on FreeBSD/ppc and ppc64.

Requested by:	jhibbits

MFC 262611:

Pull in r196874 from upstream llvm trunk:

  Fix a crash that occurs when PWD is invalid.

  MCJIT needs to be able to run in hostile environments, even when PWD
  is invalid. There's no need to crash MCJIT in this case.

  The obvious fix is to simply leave MCContext's CompilationDir empty
  when PWD can't be determined. This way, MCJIT clients,
  and other clients that link with LLVM don't need a valid working directory.

  If we do want to guarantee valid CompilationDir, that should be done
  only for clients of getCompilationDir(). This is as simple as checking
  for an empty string.

  The only current use of getCompilationDir is EmitGenDwarfInfo, which
  won't conceivably run with an invalid working dir. However, in the
  purely hypothetically and untestable case that this happens, the
  AT_comp_dir will be omitted from the compilation_unit DIE.

This should help fix assertions occurring with ports-mgmt/tinderbox,
when it is using jails, and sometimes invalidates clang's current
working directory.

Reported by:	decke

MFC 262809:

Pull in r203007 from upstream clang trunk:

  Don't produce an alias between destructors with different calling conventions.

  Fixes pr19007.

(Please note that is an LLVM PR identifier, not a FreeBSD one.)

This should fix Firefox and/or libxul crashes (due to problems with
regparm/stdcall calling conventions) on i386.

Reported by:	multiple users on freebsd-current
PR:		bin/187103

MFC 263048:

Repair recognition of "CC" as an alias for the C++ compiler, since it
was silently broken by upstream for a Windows-specific use-case.

Apparently some versions of CMake still rely on this archaic feature...

Reported by:	rakuco

MFC 263049:

Garbage collect the old way of adding the libstdc++ include directories
in clang's InitHeaderSearch.cpp.  This has been superseded by David
Chisnall's commit in r255321.

Moreover, if libc++ is used, the libstdc++ include directories should
not be in the search path at all.  These directories are now only used
if you pass -stdlib=libstdc++.

1 files changed, 102 insertions, 36 deletions

diff --git a/contrib/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp b/contrib/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
index 49ef1e7..911c14e 100644
--- a/contrib/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/contrib/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -211,7 +211,9 @@ void DAE::CollectFunctionDIs(Module &M) {
       for (unsigned SPIndex = 0, SPNum = SPs.getNumElements();
            SPIndex < SPNum; ++SPIndex) {
         DISubprogram SP(SPs.getElement(SPIndex));
-        if (!SP.Verify())
+        assert((!SP || SP.isSubprogram()) &&
+          "A MDNode in subprograms of a CU should be null or a DISubprogram.");
+        if (!SP)
           continue;
         if (Function *F = SP.getFunction())
           FunctionDIs[F] = SP;
@@ -263,8 +265,10 @@ bool DAE::DeleteDeadVarargs(Function &Fn) {
   // to pass in a smaller number of arguments into the new function.
   //
   std::vector<Value*> Args;
-  while (!Fn.use_empty()) {
-    CallSite CS(Fn.use_back());
+  for (Value::use_iterator I = Fn.use_begin(), E = Fn.use_end(); I != E; ) {
+    CallSite CS(*I++);
+    if (!CS)
+      continue;
     Instruction *Call = CS.getInstruction();
 
     // Pass all the same arguments.
@@ -330,6 +334,11 @@ bool DAE::DeleteDeadVarargs(Function &Fn) {
   if (DI != FunctionDIs.end())
     DI->second.replaceFunction(NF);
 
+  // Fix up any BlockAddresses that refer to the function.
+  Fn.replaceAllUsesWith(ConstantExpr::getBitCast(NF, Fn.getType()));
+  // Delete the bitcast that we just created, so that NF does not
+  // appear to be address-taken.
+  NF->removeDeadConstantUsers();
   // Finally, nuke the old function.
   Fn.eraseFromParent();
   return true;
@@ -343,8 +352,22 @@ bool DAE::RemoveDeadArgumentsFromCallers(Function &Fn)
   if (Fn.isDeclaration() || Fn.mayBeOverridden())
     return false;
 
-  // Functions with local linkage should already have been handled.
-  if (Fn.hasLocalLinkage())
+  // Functions with local linkage should already have been handled, except the
+  // fragile (variadic) ones which we can improve here.
+  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())
@@ -604,9 +627,20 @@ void DAE::SurveyFunction(const Function &F) {
   UseVector MaybeLiveArgUses;
   for (Function::const_arg_iterator AI = F.arg_begin(),
        E = F.arg_end(); AI != E; ++AI, ++i) {
-    // See what the effect of this use is (recording any uses that cause
-    // MaybeLive in MaybeLiveArgUses).
-    Liveness Result = SurveyUses(AI, MaybeLiveArgUses);
+    Liveness Result;
+    if (F.getFunctionType()->isVarArg()) {
+      // Variadic functions will already have a va_arg function expanded inside
+      // them, making them potentially very sensitive to ABI changes resulting
+      // from removing arguments entirely, so don't. For example AArch64 handles
+      // register and stack HFAs very differently, and this is reflected in the
+      // IR which has already been generated.
+      Result = Live;
+    } else {
+      // See what the effect of this use is (recording any uses that cause
+      // MaybeLive in MaybeLiveArgUses). 
+      Result = SurveyUses(AI, MaybeLiveArgUses);
+    }
+
     // Mark the result.
     MarkValue(CreateArg(&F, i), Result, MaybeLiveArgUses);
     // Clear the vector again for the next iteration.
@@ -695,10 +729,42 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
   FunctionType *FTy = F->getFunctionType();
   std::vector<Type*> Params;
 
+  // Keep track of if we have a live 'returned' argument
+  bool HasLiveReturnedArg = false;
+
   // Set up to build a new list of parameter attributes.
   SmallVector<AttributeSet, 8> AttributesVec;
   const AttributeSet &PAL = F->getAttributes();
 
+  // Remember which arguments are still alive.
+  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
+  // Construct the new parameter list from non-dead arguments. Also construct
+  // a new set of parameter attributes to correspond. Skip the first parameter
+  // attribute, since that belongs to the return value.
+  unsigned i = 0;
+  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
+       I != E; ++I, ++i) {
+    RetOrArg Arg = CreateArg(F, i);
+    if (LiveValues.erase(Arg)) {
+      Params.push_back(I->getType());
+      ArgAlive[i] = true;
+
+      // Get the original parameter attributes (skipping the first one, that is
+      // for the return value.
+      if (PAL.hasAttributes(i + 1)) {
+        AttrBuilder B(PAL, i + 1);
+        if (B.contains(Attribute::Returned))
+          HasLiveReturnedArg = true;
+        AttributesVec.
+          push_back(AttributeSet::get(F->getContext(), Params.size(), B));
+      }
+    } else {
+      ++NumArgumentsEliminated;
+      DEBUG(dbgs() << "DAE - Removing argument " << i << " (" << I->getName()
+            << ") from " << F->getName() << "\n");
+    }
+  }
+
   // Find out the new return value.
   Type *RetTy = FTy->getReturnType();
   Type *NRetTy = NULL;
@@ -707,7 +773,27 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
   // -1 means unused, other numbers are the new index
   SmallVector<int, 5> NewRetIdxs(RetCount, -1);
   std::vector<Type*> RetTypes;
-  if (RetTy->isVoidTy()) {
+
+  // If there is a function with a live 'returned' argument but a dead return
+  // value, then there are two possible actions:
+  // 1) Eliminate the return value and take off the 'returned' attribute on the
+  //    argument.
+  // 2) Retain the 'returned' attribute and treat the return value (but not the
+  //    entire function) as live so that it is not eliminated.
+  // 
+  // It's not clear in the general case which option is more profitable because,
+  // even in the absence of explicit uses of the return value, code generation
+  // is free to use the 'returned' attribute to do things like eliding
+  // save/restores of registers across calls. Whether or not this happens is
+  // target and ABI-specific as well as depending on the amount of register
+  // pressure, so there's no good way for an IR-level pass to figure this out.
+  //
+  // Fortunately, the only places where 'returned' is currently generated by
+  // the FE are places where 'returned' is basically free and almost always a
+  // performance win, so the second option can just be used always for now.
+  //
+  // This should be revisited if 'returned' is ever applied more liberally.
+  if (RetTy->isVoidTy() || HasLiveReturnedArg) {
     NRetTy = RetTy;
   } else {
     StructType *STy = dyn_cast<StructType>(RetTy);
@@ -777,33 +863,6 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
   if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
     AttributesVec.push_back(AttributeSet::get(NRetTy->getContext(), RAttrs));
 
-  // Remember which arguments are still alive.
-  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
-  // Construct the new parameter list from non-dead arguments. Also construct
-  // a new set of parameter attributes to correspond. Skip the first parameter
-  // attribute, since that belongs to the return value.
-  unsigned i = 0;
-  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
-       I != E; ++I, ++i) {
-    RetOrArg Arg = CreateArg(F, i);
-    if (LiveValues.erase(Arg)) {
-      Params.push_back(I->getType());
-      ArgAlive[i] = true;
-
-      // Get the original parameter attributes (skipping the first one, that is
-      // for the return value.
-      if (PAL.hasAttributes(i + 1)) {
-        AttrBuilder B(PAL, i + 1);
-        AttributesVec.
-          push_back(AttributeSet::get(F->getContext(), Params.size(), B));
-      }
-    } else {
-      ++NumArgumentsEliminated;
-      DEBUG(dbgs() << "DAE - Removing argument " << i << " (" << I->getName()
-            << ") from " << F->getName() << "\n");
-    }
-  }
-
   if (PAL.hasAttributes(AttributeSet::FunctionIndex))
     AttributesVec.push_back(AttributeSet::get(F->getContext(),
                                               PAL.getFnAttributes()));
@@ -864,6 +923,13 @@ bool DAE::RemoveDeadStuffFromFunction(Function *F) {
         // Get original parameter attributes, but skip return attributes.
         if (CallPAL.hasAttributes(i + 1)) {
           AttrBuilder B(CallPAL, i + 1);
+          // If the return type has changed, then get rid of 'returned' on the
+          // call site. The alternative is to make all 'returned' attributes on
+          // call sites keep the return value alive just like 'returned'
+          // attributes on function declaration but it's less clearly a win
+          // and this is not an expected case anyway
+          if (NRetTy != RetTy && B.contains(Attribute::Returned))
+            B.removeAttribute(Attribute::Returned);
           AttributesVec.
             push_back(AttributeSet::get(F->getContext(), Args.size(), B));
         }