Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release:

MFC r309142 (by emaste):

Add WITH_LLD_AS_LD build knob

If set it installs LLD as /usr/bin/ld.  LLD (as of version 3.9) is not
capable of linking the world and kernel, but can self-host and link many
substantial applications. GNU ld continues to be used for the world and
kernel build, regardless of how this knob is set.

It is on by default for arm64, and off for all other CPU architectures.

Sponsored by:	The FreeBSD Foundation

MFC r310840:

Reapply 310775, now it also builds correctly if lldb is disabled:

Move llvm-objdump from CLANG_EXTRAS to installed by default

We currently install three tools from binutils 2.17.50: as, ld, and
objdump. Work is underway to migrate to a permissively-licensed
tool-chain, with one goal being the retirement of binutils 2.17.50.

LLVM's llvm-objdump is intended to be compatible with GNU objdump
although it is currently missing some options and may have formatting
differences. Enable it by default for testing and further investigation.
It may later be changed to install as /usr/bin/objdump, it becomes a
fully viable replacement.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D8879

MFC r312855 (by emaste):

Rename LLD_AS_LD to LLD_IS_LD, for consistency with CLANG_IS_CC

Reported by:	Dan McGregor <dan.mcgregor usask.ca>

MFC r313559 | glebius | 2017-02-10 18:34:48 +0100 (Fri, 10 Feb 2017) | 5 lines

Don't check struct rtentry on FreeBSD, it is an internal kernel structure.
On other systems it may be API structure for SIOCADDRT/SIOCDELRT.

Reviewed by:	emaste, dim

MFC r314152 (by jkim):

Remove an assembler flag, which is redundant since r309124.  The upstream
took care of it by introducing a macro NO_EXEC_STACK_DIRECTIVE.

http://llvm.org/viewvc/llvm-project?rev=273500&view=rev

Reviewed by:	dim

MFC r314564:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
4.0.0 (branches/release_40 296509).  The release will follow soon.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Also note that as of 4.0.0, lld should be able to link the base system
on amd64 and aarch64.  See the WITH_LLD_IS_LLD setting in src.conf(5).
Though please be aware that this is work in progress.

Release notes for llvm, clang and lld will be available here:
<http://releases.llvm.org/4.0.0/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Jan Beich, Antoine Brodin and Eric Fiselier for
their help.

Relnotes:	yes
Exp-run:	antoine
PR:		215969, 216008

MFC r314708:

For now, revert r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

This commit is the cause of excessive compile times on skein_block.c
(and possibly other files) during kernel builds on amd64.

We never saw the problematic behavior described in this upstream commit,
so for now it is better to revert it.  An upstream bug has been filed
here: https://bugs.llvm.org/show_bug.cgi?id=32142

Reported by:	mjg

MFC r314795:

Reapply r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

Pull in r296992 from upstream llvm trunk (by Sanjoy Das):

  [SCEV] Decrease the recursion threshold for CompareValueComplexity

  Fixes PR32142.

  r287232 accidentally increased the recursion threshold for
  CompareValueComplexity from 2 to 32.  This change reverses that
  change by introducing a separate flag for CompareValueComplexity's
  threshold.

The latter revision fixes the excessive compile times for skein_block.c.

MFC r314907 | mmel | 2017-03-08 12:40:27 +0100 (Wed, 08 Mar 2017) | 7 lines

Unbreak ARMv6 world.

The new compiler_rt library imported with clang 4.0.0 have several fatal
issues (non-functional __udivsi3 for example) with ARM specific instrict
functions. As temporary workaround, until upstream solve these problems,
disable all thumb[1][2] related feature.

MFC r315016:

Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release.
We were already very close to the last release candidate, so this is a
pretty minor update.

Relnotes:	yes

MFC r316005:

Revert r314907, and pull in r298713 from upstream compiler-rt trunk (by
Weiming Zhao):

  builtins: Select correct code fragments when compiling for Thumb1/Thum2/ARM ISA.

  Summary:
  Value of __ARM_ARCH_ISA_THUMB isn't based on the actual compilation
  mode (-mthumb, -marm), it reflect's capability of given CPU.

  Due to this:
   - use  __tbumb__ and __thumb2__ insteand of __ARM_ARCH_ISA_THUMB
   - use '.thumb' directive consistently  in all affected files
   - decorate all thumb functions using
     DEFINE_COMPILERRT_THUMB_FUNCTION()

  ---------
  Note: This patch doesn't fix broken Thumb1 variant of __udivsi3 !

  Reviewers: weimingz, rengolin, compnerd

  Subscribers: aemerson, dim

  Differential Revision: https://reviews.llvm.org/D30938

Discussed with:	mmel

1 files changed, 145 insertions, 71 deletions

diff --git a/contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp b/contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp
index e82c07f..a40079c 100644
--- a/contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/contrib/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -14,6 +14,7 @@
 
 #include "llvm/Transforms/Utils/Cloning.h"
 #include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
@@ -228,7 +229,7 @@ static Value *getUnwindDestTokenHelper(Instruction *EHPad,
             Instruction *ChildPad = cast<Instruction>(Child);
             auto Memo = MemoMap.find(ChildPad);
             if (Memo == MemoMap.end()) {
-              // Haven't figure out this child pad yet; queue it.
+              // Haven't figured out this child pad yet; queue it.
               Worklist.push_back(ChildPad);
               continue;
             }
@@ -366,6 +367,10 @@ static Value *getUnwindDestToken(Instruction *EHPad,
   // search up the chain to try to find a funclet with information.  Put
   // null entries in the memo map to avoid re-processing as we go up.
   MemoMap[EHPad] = nullptr;
+#ifndef NDEBUG
+  SmallPtrSet<Instruction *, 4> TempMemos;
+  TempMemos.insert(EHPad);
+#endif
   Instruction *LastUselessPad = EHPad;
   Value *AncestorToken;
   for (AncestorToken = getParentPad(EHPad);
@@ -374,6 +379,13 @@ static Value *getUnwindDestToken(Instruction *EHPad,
     // Skip over catchpads since they just follow their catchswitches.
     if (isa<CatchPadInst>(AncestorPad))
       continue;
+    // If the MemoMap had an entry mapping AncestorPad to nullptr, since we
+    // haven't yet called getUnwindDestTokenHelper for AncestorPad in this
+    // call to getUnwindDestToken, that would mean that AncestorPad had no
+    // information in itself, its descendants, or its ancestors.  If that
+    // were the case, then we should also have recorded the lack of information
+    // for the descendant that we're coming from.  So assert that we don't
+    // find a null entry in the MemoMap for AncestorPad.
     assert(!MemoMap.count(AncestorPad) || MemoMap[AncestorPad]);
     auto AncestorMemo = MemoMap.find(AncestorPad);
     if (AncestorMemo == MemoMap.end()) {
@@ -384,25 +396,85 @@ static Value *getUnwindDestToken(Instruction *EHPad,
     if (UnwindDestToken)
       break;
     LastUselessPad = AncestorPad;
+    MemoMap[LastUselessPad] = nullptr;
+#ifndef NDEBUG
+    TempMemos.insert(LastUselessPad);
+#endif
   }
 
-  // Since the whole tree under LastUselessPad has no information, it all must
-  // match UnwindDestToken; record that to avoid repeating the search.
+  // We know that getUnwindDestTokenHelper was called on LastUselessPad and
+  // returned nullptr (and likewise for EHPad and any of its ancestors up to
+  // LastUselessPad), so LastUselessPad has no information from below.  Since
+  // getUnwindDestTokenHelper must investigate all downward paths through
+  // no-information nodes to prove that a node has no information like this,
+  // and since any time it finds information it records it in the MemoMap for
+  // not just the immediately-containing funclet but also any ancestors also
+  // exited, it must be the case that, walking downward from LastUselessPad,
+  // visiting just those nodes which have not been mapped to an unwind dest
+  // by getUnwindDestTokenHelper (the nullptr TempMemos notwithstanding, since
+  // they are just used to keep getUnwindDestTokenHelper from repeating work),
+  // any node visited must have been exhaustively searched with no information
+  // for it found.
   SmallVector<Instruction *, 8> Worklist(1, LastUselessPad);
   while (!Worklist.empty()) {
     Instruction *UselessPad = Worklist.pop_back_val();
-    assert(!MemoMap.count(UselessPad) || MemoMap[UselessPad] == nullptr);
+    auto Memo = MemoMap.find(UselessPad);
+    if (Memo != MemoMap.end() && Memo->second) {
+      // Here the name 'UselessPad' is a bit of a misnomer, because we've found
+      // that it is a funclet that does have information about unwinding to
+      // a particular destination; its parent was a useless pad.
+      // Since its parent has no information, the unwind edge must not escape
+      // the parent, and must target a sibling of this pad.  This local unwind
+      // gives us no information about EHPad.  Leave it and the subtree rooted
+      // at it alone.
+      assert(getParentPad(Memo->second) == getParentPad(UselessPad));
+      continue;
+    }
+    // We know we don't have information for UselesPad.  If it has an entry in
+    // the MemoMap (mapping it to nullptr), it must be one of the TempMemos
+    // added on this invocation of getUnwindDestToken; if a previous invocation
+    // recorded nullptr, it would have had to prove that the ancestors of
+    // UselessPad, which include LastUselessPad, had no information, and that
+    // in turn would have required proving that the descendants of
+    // LastUselesPad, which include EHPad, have no information about
+    // LastUselessPad, which would imply that EHPad was mapped to nullptr in
+    // the MemoMap on that invocation, which isn't the case if we got here.
+    assert(!MemoMap.count(UselessPad) || TempMemos.count(UselessPad));
+    // Assert as we enumerate users that 'UselessPad' doesn't have any unwind
+    // information that we'd be contradicting by making a map entry for it
+    // (which is something that getUnwindDestTokenHelper must have proved for
+    // us to get here).  Just assert on is direct users here; the checks in
+    // this downward walk at its descendants will verify that they don't have
+    // any unwind edges that exit 'UselessPad' either (i.e. they either have no
+    // unwind edges or unwind to a sibling).
     MemoMap[UselessPad] = UnwindDestToken;
     if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(UselessPad)) {
-      for (BasicBlock *HandlerBlock : CatchSwitch->handlers())
-        for (User *U : HandlerBlock->getFirstNonPHI()->users())
+      assert(CatchSwitch->getUnwindDest() == nullptr && "Expected useless pad");
+      for (BasicBlock *HandlerBlock : CatchSwitch->handlers()) {
+        auto *CatchPad = HandlerBlock->getFirstNonPHI();
+        for (User *U : CatchPad->users()) {
+          assert(
+              (!isa<InvokeInst>(U) ||
+               (getParentPad(
+                    cast<InvokeInst>(U)->getUnwindDest()->getFirstNonPHI()) ==
+                CatchPad)) &&
+              "Expected useless pad");
           if (isa<CatchSwitchInst>(U) || isa<CleanupPadInst>(U))
             Worklist.push_back(cast<Instruction>(U));
+        }
+      }
     } else {
       assert(isa<CleanupPadInst>(UselessPad));
-      for (User *U : UselessPad->users())
+      for (User *U : UselessPad->users()) {
+        assert(!isa<CleanupReturnInst>(U) && "Expected useless pad");
+        assert((!isa<InvokeInst>(U) ||
+                (getParentPad(
+                     cast<InvokeInst>(U)->getUnwindDest()->getFirstNonPHI()) ==
+                 UselessPad)) &&
+               "Expected useless pad");
         if (isa<CatchSwitchInst>(U) || isa<CleanupPadInst>(U))
           Worklist.push_back(cast<Instruction>(U));
+      }
     }
   }
 
@@ -463,37 +535,7 @@ static BasicBlock *HandleCallsInBlockInlinedThroughInvoke(
 #endif // NDEBUG
     }
 
-    // Convert this function call into an invoke instruction.  First, split the
-    // basic block.
-    BasicBlock *Split =
-        BB->splitBasicBlock(CI->getIterator(), CI->getName() + ".noexc");
-
-    // Delete the unconditional branch inserted by splitBasicBlock
-    BB->getInstList().pop_back();
-
-    // Create the new invoke instruction.
-    SmallVector<Value*, 8> InvokeArgs(CI->arg_begin(), CI->arg_end());
-    SmallVector<OperandBundleDef, 1> OpBundles;
-
-    CI->getOperandBundlesAsDefs(OpBundles);
-
-    // Note: we're round tripping operand bundles through memory here, and that
-    // can potentially be avoided with a cleverer API design that we do not have
-    // as of this time.
-
-    InvokeInst *II =
-        InvokeInst::Create(CI->getCalledValue(), Split, UnwindEdge, InvokeArgs,
-                           OpBundles, CI->getName(), BB);
-    II->setDebugLoc(CI->getDebugLoc());
-    II->setCallingConv(CI->getCallingConv());
-    II->setAttributes(CI->getAttributes());
-    
-    // Make sure that anything using the call now uses the invoke!  This also
-    // updates the CallGraph if present, because it uses a WeakVH.
-    CI->replaceAllUsesWith(II);
-
-    // Delete the original call
-    Split->getInstList().pop_front();
+    changeToInvokeAndSplitBasicBlock(CI, UnwindEdge);
     return BB;
   }
   return nullptr;
@@ -718,7 +760,7 @@ static void PropagateParallelLoopAccessMetadata(CallSite CS,
 
 /// When inlining a function that contains noalias scope metadata,
 /// this metadata needs to be cloned so that the inlined blocks
-/// have different "unqiue scopes" at every call site. Were this not done, then
+/// have different "unique scopes" at every call site. Were this not done, then
 /// aliasing scopes from a function inlined into a caller multiple times could
 /// not be differentiated (and this would lead to miscompiles because the
 /// non-aliasing property communicated by the metadata could have
@@ -1053,8 +1095,10 @@ static void AddAliasScopeMetadata(CallSite CS, ValueToValueMapTy &VMap,
 /// If the inlined function has non-byval align arguments, then
 /// add @llvm.assume-based alignment assumptions to preserve this information.
 static void AddAlignmentAssumptions(CallSite CS, InlineFunctionInfo &IFI) {
-  if (!PreserveAlignmentAssumptions)
+  if (!PreserveAlignmentAssumptions || !IFI.GetAssumptionCache)
     return;
+
+  AssumptionCache *AC = &(*IFI.GetAssumptionCache)(*CS.getCaller());
   auto &DL = CS.getCaller()->getParent()->getDataLayout();
 
   // To avoid inserting redundant assumptions, we should check for assumptions
@@ -1077,13 +1121,12 @@ static void AddAlignmentAssumptions(CallSite CS, InlineFunctionInfo &IFI) {
       // If we can already prove the asserted alignment in the context of the
       // caller, then don't bother inserting the assumption.
       Value *Arg = CS.getArgument(I->getArgNo());
-      if (getKnownAlignment(Arg, DL, CS.getInstruction(),
-                            &IFI.ACT->getAssumptionCache(*CS.getCaller()),
-                            &DT) >= Align)
+      if (getKnownAlignment(Arg, DL, CS.getInstruction(), AC, &DT) >= Align)
         continue;
 
-      IRBuilder<>(CS.getInstruction())
-          .CreateAlignmentAssumption(DL, Arg, Align);
+      CallInst *NewAssumption = IRBuilder<>(CS.getInstruction())
+                                    .CreateAlignmentAssumption(DL, Arg, Align);
+      AC->registerAssumption(NewAssumption);
     }
   }
 }
@@ -1194,12 +1237,13 @@ static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
     if (ByValAlignment <= 1)  // 0 = unspecified, 1 = no particular alignment.
       return Arg;
 
+    AssumptionCache *AC =
+        IFI.GetAssumptionCache ? &(*IFI.GetAssumptionCache)(*Caller) : nullptr;
     const DataLayout &DL = Caller->getParent()->getDataLayout();
 
     // If the pointer is already known to be sufficiently aligned, or if we can
     // round it up to a larger alignment, then we don't need a temporary.
-    if (getOrEnforceKnownAlignment(Arg, ByValAlignment, DL, TheCall,
-                                   &IFI.ACT->getAssumptionCache(*Caller)) >=
+    if (getOrEnforceKnownAlignment(Arg, ByValAlignment, DL, TheCall, AC) >=
         ByValAlignment)
       return Arg;
     
@@ -1304,7 +1348,7 @@ static bool allocaWouldBeStaticInEntry(const AllocaInst *AI ) {
 /// Update inlined instructions' line numbers to
 /// to encode location where these instructions are inlined.
 static void fixupLineNumbers(Function *Fn, Function::iterator FI,
-                             Instruction *TheCall) {
+                             Instruction *TheCall, bool CalleeHasDebugInfo) {
   const DebugLoc &TheCallDL = TheCall->getDebugLoc();
   if (!TheCallDL)
     return;
@@ -1326,22 +1370,26 @@ static void fixupLineNumbers(Function *Fn, Function::iterator FI,
   for (; FI != Fn->end(); ++FI) {
     for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
          BI != BE; ++BI) {
-      DebugLoc DL = BI->getDebugLoc();
-      if (!DL) {
-        // If the inlined instruction has no line number, make it look as if it
-        // originates from the call location. This is important for
-        // ((__always_inline__, __nodebug__)) functions which must use caller
-        // location for all instructions in their function body.
-
-        // Don't update static allocas, as they may get moved later.
-        if (auto *AI = dyn_cast<AllocaInst>(BI))
-          if (allocaWouldBeStaticInEntry(AI))
-            continue;
-
-        BI->setDebugLoc(TheCallDL);
-      } else {
-        BI->setDebugLoc(updateInlinedAtInfo(DL, InlinedAtNode, BI->getContext(), IANodes));
+      if (DebugLoc DL = BI->getDebugLoc()) {
+        BI->setDebugLoc(
+            updateInlinedAtInfo(DL, InlinedAtNode, BI->getContext(), IANodes));
+        continue;
       }
+
+      if (CalleeHasDebugInfo)
+        continue;
+      
+      // If the inlined instruction has no line number, make it look as if it
+      // originates from the call location. This is important for
+      // ((__always_inline__, __nodebug__)) functions which must use caller
+      // location for all instructions in their function body.
+
+      // Don't update static allocas, as they may get moved later.
+      if (auto *AI = dyn_cast<AllocaInst>(BI))
+        if (allocaWouldBeStaticInEntry(AI))
+          continue;
+
+      BI->setDebugLoc(TheCallDL);
     }
   }
 }
@@ -1597,8 +1645,11 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
     if (IFI.CG)
       UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI);
 
-    // Update inlined instructions' line number information.
-    fixupLineNumbers(Caller, FirstNewBlock, TheCall);
+    // For 'nodebug' functions, the associated DISubprogram is always null.
+    // Conservatively avoid propagating the callsite debug location to
+    // instructions inlined from a function whose DISubprogram is not null.
+    fixupLineNumbers(Caller, FirstNewBlock, TheCall,
+                     CalledFunc->getSubprogram() != nullptr);
 
     // Clone existing noalias metadata if necessary.
     CloneAliasScopeMetadata(CS, VMap);
@@ -1609,10 +1660,15 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
     // Propagate llvm.mem.parallel_loop_access if necessary.
     PropagateParallelLoopAccessMetadata(CS, VMap);
 
-    // FIXME: We could register any cloned assumptions instead of clearing the
-    // whole function's cache.
-    if (IFI.ACT)
-      IFI.ACT->getAssumptionCache(*Caller).clear();
+    // Register any cloned assumptions.
+    if (IFI.GetAssumptionCache)
+      for (BasicBlock &NewBlock :
+           make_range(FirstNewBlock->getIterator(), Caller->end()))
+        for (Instruction &I : NewBlock) {
+          if (auto *II = dyn_cast<IntrinsicInst>(&I))
+            if (II->getIntrinsicID() == Intrinsic::assume)
+              (*IFI.GetAssumptionCache)(*Caller).registerAssumption(II);
+        }
   }
 
   // If there are any alloca instructions in the block that used to be the entry
@@ -1708,6 +1764,9 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
     IRBuilder<> builder(&FirstNewBlock->front());
     for (unsigned ai = 0, ae = IFI.StaticAllocas.size(); ai != ae; ++ai) {
       AllocaInst *AI = IFI.StaticAllocas[ai];
+      // Don't mark swifterror allocas. They can't have bitcast uses.
+      if (AI->isSwiftError())
+        continue;
 
       // If the alloca is already scoped to something smaller than the whole
       // function then there's no need to add redundant, less accurate markers.
@@ -1949,6 +2008,20 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
     std::swap(Returns, NormalReturns);
   }
 
+  // Now that all of the transforms on the inlined code have taken place but
+  // before we splice the inlined code into the CFG and lose track of which
+  // blocks were actually inlined, collect the call sites. We only do this if
+  // call graph updates weren't requested, as those provide value handle based
+  // tracking of inlined call sites instead.
+  if (InlinedFunctionInfo.ContainsCalls && !IFI.CG) {
+    // Otherwise just collect the raw call sites that were inlined.
+    for (BasicBlock &NewBB :
+         make_range(FirstNewBlock->getIterator(), Caller->end()))
+      for (Instruction &I : NewBB)
+        if (auto CS = CallSite(&I))
+          IFI.InlinedCallSites.push_back(CS);
+  }
+
   // If we cloned in _exactly one_ basic block, and if that block ends in a
   // return instruction, we splice the body of the inlined callee directly into
   // the calling basic block.
@@ -2130,9 +2203,10 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
   // the entries are the same or undef).  If so, remove the PHI so it doesn't
   // block other optimizations.
   if (PHI) {
+    AssumptionCache *AC =
+        IFI.GetAssumptionCache ? &(*IFI.GetAssumptionCache)(*Caller) : nullptr;
     auto &DL = Caller->getParent()->getDataLayout();
-    if (Value *V = SimplifyInstruction(PHI, DL, nullptr, nullptr,
-                                       &IFI.ACT->getAssumptionCache(*Caller))) {
+    if (Value *V = SimplifyInstruction(PHI, DL, nullptr, nullptr, AC)) {
       PHI->replaceAllUsesWith(V);
       PHI->eraseFromParent();
     }