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, 78 insertions, 7 deletions

diff --git a/contrib/llvm/lib/Analysis/DependenceAnalysis.cpp b/contrib/llvm/lib/Analysis/DependenceAnalysis.cpp
index cbc71bd..3b3e2ef 100644
--- a/contrib/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/contrib/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -24,11 +24,11 @@
 // Both of these are conservative weaknesses;
 // that is, not a source of correctness problems.
 //
-// The implementation depends on the GEP instruction to
-// differentiate subscripts. Since Clang linearizes subscripts
-// for most arrays, we give up some precision (though the existing MIV tests
-// will help). We trust that the GEP instruction will eventually be extended.
-// In the meantime, we should explore Maslov's ideas about delinearization.
+// The implementation depends on the GEP instruction to differentiate
+// subscripts. Since Clang linearizes some array subscripts, the dependence
+// analysis is using SCEV->delinearize to recover the representation of multiple
+// subscripts, and thus avoid the more expensive and less precise MIV tests. The
+// delinearization is controlled by the flag -da-delinearize.
 //
 // We should pay some careful attention to the possibility of integer overflow
 // in the implementation of the various tests. This could happen with Add,
@@ -61,6 +61,7 @@
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/Operator.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/InstIterator.h"
@@ -104,6 +105,10 @@ STATISTIC(BanerjeeApplications, "Banerjee applications");
 STATISTIC(BanerjeeIndependence, "Banerjee independence");
 STATISTIC(BanerjeeSuccesses, "Banerjee successes");
 
+static cl::opt<bool>
+Delinearize("da-delinearize", cl::init(false), cl::Hidden, cl::ZeroOrMore,
+            cl::desc("Try to delinearize array references."));
+
 //===----------------------------------------------------------------------===//
 // basics
 
@@ -508,7 +513,7 @@ bool DependenceAnalysis::intersectConstraints(Constraint *X,
       APInt Xr = Xtop; // though they're just going to be overwritten
       APInt::sdivrem(Xtop, Xbot, Xq, Xr);
       APInt Yq = Ytop;
-      APInt Yr = Ytop;;
+      APInt Yr = Ytop;
       APInt::sdivrem(Ytop, Ybot, Yq, Yr);
       if (Xr != 0 || Yr != 0) {
         X->setEmpty();
@@ -2951,6 +2956,11 @@ const SCEV *DependenceAnalysis::addToCoefficient(const SCEV *Expr,
                              AddRec->getLoop(),
                              AddRec->getNoWrapFlags());
   }
+  if (SE->isLoopInvariant(AddRec, TargetLoop))
+    return SE->getAddRecExpr(AddRec,
+			     Value,
+			     TargetLoop,
+			     SCEV::FlagAnyWrap);
   return SE->getAddRecExpr(addToCoefficient(AddRec->getStart(),
                                             TargetLoop, Value),
                            AddRec->getStepRecurrence(*SE),
@@ -2972,7 +2982,7 @@ const SCEV *DependenceAnalysis::addToCoefficient(const SCEV *Expr,
 bool DependenceAnalysis::propagate(const SCEV *&Src,
                                    const SCEV *&Dst,
                                    SmallBitVector &Loops,
-                                   SmallVector<Constraint, 4> &Constraints,
+                                   SmallVectorImpl<Constraint> &Constraints,
                                    bool &Consistent) {
   bool Result = false;
   for (int LI = Loops.find_first(); LI >= 0; LI = Loops.find_next(LI)) {
@@ -3166,6 +3176,55 @@ void DependenceAnalysis::updateDirection(Dependence::DVEntry &Level,
     llvm_unreachable("constraint has unexpected kind");
 }
 
+/// Check if we can delinearize the subscripts. If the SCEVs representing the
+/// source and destination array references are recurrences on a nested loop,
+/// this function flattens the nested recurrences into seperate recurrences
+/// for each loop level.
+bool
+DependenceAnalysis::tryDelinearize(const SCEV *SrcSCEV, const SCEV *DstSCEV,
+                                   SmallVectorImpl<Subscript> &Pair) const {
+  const SCEVAddRecExpr *SrcAR = dyn_cast<SCEVAddRecExpr>(SrcSCEV);
+  const SCEVAddRecExpr *DstAR = dyn_cast<SCEVAddRecExpr>(DstSCEV);
+  if (!SrcAR || !DstAR || !SrcAR->isAffine() || !DstAR->isAffine())
+    return false;
+
+  SmallVector<const SCEV *, 4> SrcSubscripts, DstSubscripts, SrcSizes, DstSizes;
+  SrcAR->delinearize(*SE, SrcSubscripts, SrcSizes);
+  DstAR->delinearize(*SE, DstSubscripts, DstSizes);
+
+  int size = SrcSubscripts.size();
+  int dstSize = DstSubscripts.size();
+  if (size != dstSize || size < 2)
+    return false;
+
+#ifndef NDEBUG
+  DEBUG(errs() << "\nSrcSubscripts: ");
+  for (int i = 0; i < size; i++)
+    DEBUG(errs() << *SrcSubscripts[i]);
+  DEBUG(errs() << "\nDstSubscripts: ");
+  for (int i = 0; i < size; i++)
+    DEBUG(errs() << *DstSubscripts[i]);
+#endif
+
+  // The delinearization transforms a single-subscript MIV dependence test into
+  // a multi-subscript SIV dependence test that is easier to compute. So we
+  // resize Pair to contain as many pairs of subscripts as the delinearization
+  // has found, and then initialize the pairs following the delinearization.
+  Pair.resize(size);
+  for (int i = 0; i < size; ++i) {
+    Pair[i].Src = SrcSubscripts[i];
+    Pair[i].Dst = DstSubscripts[i];
+
+    // FIXME: we should record the bounds SrcSizes[i] and DstSizes[i] that the
+    // delinearization has found, and add these constraints to the dependence
+    // check to avoid memory accesses overflow from one dimension into another.
+    // This is related to the problem of determining the existence of data
+    // dependences in array accesses using a different number of subscripts: in
+    // C one can access an array A[100][100]; as A[0][9999], *A[9999], etc.
+  }
+
+  return true;
+}
 
 //===----------------------------------------------------------------------===//
 
@@ -3275,6 +3334,12 @@ Dependence *DependenceAnalysis::depends(Instruction *Src,
     Pair[0].Dst = DstSCEV;
   }
 
+  if (Delinearize && Pairs == 1 && CommonLevels > 1 &&
+      tryDelinearize(Pair[0].Src, Pair[0].Dst, Pair)) {
+    DEBUG(dbgs() << "    delinerized GEP\n");
+    Pairs = Pair.size();
+  }
+
   for (unsigned P = 0; P < Pairs; ++P) {
     Pair[P].Loops.resize(MaxLevels + 1);
     Pair[P].GroupLoops.resize(MaxLevels + 1);
@@ -3693,6 +3758,12 @@ const  SCEV *DependenceAnalysis::getSplitIteration(const Dependence *Dep,
     Pair[0].Dst = DstSCEV;
   }
 
+  if (Delinearize && Pairs == 1 && CommonLevels > 1 &&
+      tryDelinearize(Pair[0].Src, Pair[0].Dst, Pair)) {
+    DEBUG(dbgs() << "    delinerized GEP\n");
+    Pairs = Pair.size();
+  }
+
   for (unsigned P = 0; P < Pairs; ++P) {
     Pair[P].Loops.resize(MaxLevels + 1);
     Pair[P].GroupLoops.resize(MaxLevels + 1);