Speculatively revert 112699 and 112702, they seem to be causing

self host errors on clang-x86-64.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112719 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 82 insertions, 80 deletions

diff --git a/lib/CodeGen/DwarfEHPrepare.cpp b/lib/CodeGen/DwarfEHPrepare.cpp
index 550fd3e25f..2522d0b67e 100644
--- a/lib/CodeGen/DwarfEHPrepare.cpp
+++ b/lib/CodeGen/DwarfEHPrepare.cpp
@@ -25,12 +25,12 @@
 #include "llvm/Support/CallSite.h"
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/SSAUpdater.h"
 using namespace llvm;
 
 STATISTIC(NumLandingPadsSplit,     "Number of landing pads split");
 STATISTIC(NumUnwindsLowered,       "Number of unwind instructions lowered");
 STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved");
+STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced");
 
 namespace {
   class DwarfEHPrepare : public FunctionPass {
@@ -62,11 +62,24 @@ namespace {
     typedef SmallPtrSet<BasicBlock*, 8> BBSet;
     BBSet LandingPads;
 
+    // Stack temporary used to hold eh.exception values.
+    AllocaInst *ExceptionValueVar;
+
     bool NormalizeLandingPads();
     bool LowerUnwinds();
     bool MoveExceptionValueCalls();
+    bool FinishStackTemporaries();
 
     Instruction *CreateExceptionValueCall(BasicBlock *BB);
+    Instruction *CreateValueLoad(BasicBlock *BB);
+
+    /// CreateReadOfExceptionValue - Return the result of the eh.exception
+    /// intrinsic by calling the intrinsic if in a landing pad, or loading it
+    /// from the exception value variable otherwise.
+    Instruction *CreateReadOfExceptionValue(BasicBlock *BB) {
+      return LandingPads.count(BB) ?
+        CreateExceptionValueCall(BB) : CreateValueLoad(BB);
+    }
 
     /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still
     /// use the "llvm.eh.catch.all.value" call need to convert to using its
@@ -104,7 +117,7 @@ namespace {
 
     virtual bool runOnFunction(Function &Fn);
 
-    // getAnalysisUsage - We need the dominator tree for handling URoR.
+    // getAnalysisUsage - We need dominance frontiers for memory promotion.
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       AU.addRequired<DominatorTree>();
       AU.addPreserved<DominatorTree>();
@@ -504,7 +517,7 @@ bool DwarfEHPrepare::LowerUnwinds() {
 
     // Create the call...
     CallInst *CI = CallInst::Create(RewindFunction,
-                                    CreateExceptionValueCall(TI->getParent()),
+                                    CreateReadOfExceptionValue(TI->getParent()),
                                     "", TI);
     CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
     // ...followed by an UnreachableInst.
@@ -520,11 +533,9 @@ bool DwarfEHPrepare::LowerUnwinds() {
 }
 
 /// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from
-/// landing pads by replacing calls outside of landing pads with direct use of
-/// a register holding the appropriate value; this requires adding calls inside
-/// all landing pads to initialize the register.  Also, move eh.exception calls
-/// inside landing pads to the start of the landing pad (optional, but may make
-/// things simpler for later passes).
+/// landing pads by replacing calls outside of landing pads with loads from a
+/// stack temporary.  Move eh.exception calls inside landing pads to the start
+/// of the landing pad (optional, but may make things simpler for later passes).
 bool DwarfEHPrepare::MoveExceptionValueCalls() {
   // If the eh.exception intrinsic is not declared in the module then there is
   // nothing to do.  Speed up compilation by checking for this common case.
@@ -534,87 +545,49 @@ bool DwarfEHPrepare::MoveExceptionValueCalls() {
 
   bool Changed = false;
 
-  // Move calls to eh.exception that are inside a landing pad to the start of
-  // the landing pad.
-  for (BBSet::const_iterator LI = LandingPads.begin(), LE = LandingPads.end();
-       LI != LE; ++LI) {
-    BasicBlock *LP = *LI;
-    for (BasicBlock::iterator II = LP->getFirstNonPHIOrDbg(), IE = LP->end();
-         II != IE;)
-      if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) {
-        // Found a call to eh.exception.
-        if (!EI->use_empty()) {
-          // If there is already a call to eh.exception at the start of the
-          // landing pad, then get hold of it; otherwise create such a call.
-          Value *CallAtStart = CreateExceptionValueCall(LP);
-
-          // If the call was at the start of a landing pad then leave it alone.
-          if (EI == CallAtStart)
-            continue;
-          EI->replaceAllUsesWith(CallAtStart);
+  for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
+    for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;)
+      if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++))
+        if (CI->getIntrinsicID() == Intrinsic::eh_exception) {
+          if (!CI->use_empty()) {
+            Value *ExceptionValue = CreateReadOfExceptionValue(BB);
+            if (CI == ExceptionValue) {
+              // The call was at the start of a landing pad - leave it alone.
+              assert(LandingPads.count(BB) &&
+                     "Created eh.exception call outside landing pad!");
+              continue;
+            }
+            CI->replaceAllUsesWith(ExceptionValue);
+          }
+          CI->eraseFromParent();
+          ++NumExceptionValuesMoved;
+          Changed = true;
         }
-        EI->eraseFromParent();
-        ++NumExceptionValuesMoved;
-        Changed = true;
-      }
   }
 
-  // Look for calls to eh.exception that are not in a landing pad.  If one is
-  // found, then a register that holds the exception value will be created in
-  // each landing pad, and the SSAUpdater will be used to compute the values
-  // returned by eh.exception calls outside of landing pads.
-  SSAUpdater SSA;
-
-  // Remember where we found the eh.exception call, to avoid rescanning earlier
-  // basic blocks which we already know contain no eh.exception calls.
-  bool FoundCallOutsideLandingPad = false;
-  Function::iterator BB = F->begin();
-  for (Function::iterator BE = F->end(); BB != BE; ++BB) {
-    // Skip over landing pads.
-    if (LandingPads.count(BB))
-      continue;
-
-    for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
-         II != IE; ++II)
-      if (isa<EHExceptionInst>(II)) {
-        SSA.Initialize(II->getType(), II->getName());
-        FoundCallOutsideLandingPad = true;
-        break;
-      }
+  return Changed;
+}
 
-    if (FoundCallOutsideLandingPad)
-      break;
-  }
+/// FinishStackTemporaries - If we introduced a stack variable to hold the
+/// exception value then initialize it in each landing pad.
+bool DwarfEHPrepare::FinishStackTemporaries() {
+  if (!ExceptionValueVar)
+    // Nothing to do.
+    return false;
 
-  // If all calls to eh.exception are in landing pads then we are done.
-  if (!FoundCallOutsideLandingPad)
-    return Changed;
+  bool Changed = false;
 
-  // Add a call to eh.exception at the start of each landing pad, and tell the
-  // SSAUpdater that this is the value produced by the landing pad.
+  // Make sure that there is a store of the exception value at the start of
+  // each landing pad.
   for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end();
-       LI != LE; ++LI)
-    SSA.AddAvailableValue(*LI, CreateExceptionValueCall(*LI));
-
-  // Now turn all calls to eh.exception that are not in a landing pad into a use
-  // of the appropriate register.
-  for (Function::iterator BE = F->end(); BB != BE; ++BB) {
-    // Skip over landing pads.
-    if (LandingPads.count(BB))
-      continue;
-
-    for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
-         II != IE;)
-      if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) {
-        // Found a call to eh.exception, replace it with the value from any
-        // upstream landing pad(s).
-        EI->replaceAllUsesWith(SSA.GetValueAtEndOfBlock(BB));
-        EI->eraseFromParent();
-        ++NumExceptionValuesMoved;
-      }
+       LI != LE; ++LI) {
+    Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI);
+    Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar);
+    Store->insertAfter(ExceptionValue);
+    Changed = true;
   }
 
-  return true;
+  return Changed;
 }
 
 /// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at
@@ -637,11 +610,35 @@ Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
   return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start);
 }
 
+/// CreateValueLoad - Insert a load of the exception value stack variable
+/// (creating it if necessary) at the start of the basic block (unless
+/// there already is a load, in which case the existing load is returned).
+Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) {
+  Instruction *Start = BB->getFirstNonPHIOrDbg();
+  // Is this a load of the exception temporary?
+  if (ExceptionValueVar)
+    if (LoadInst* LI = dyn_cast<LoadInst>(Start))
+      if (LI->getPointerOperand() == ExceptionValueVar)
+        // Reuse the existing load.
+        return Start;
+
+  // Create the temporary if we didn't already.
+  if (!ExceptionValueVar) {
+    ExceptionValueVar = new AllocaInst(PointerType::getUnqual(
+           Type::getInt8Ty(BB->getContext())), "eh.value", F->begin()->begin());
+    ++NumStackTempsIntroduced;
+  }
+
+  // Load the value.
+  return new LoadInst(ExceptionValueVar, "eh.value.load", Start);
+}
+
 bool DwarfEHPrepare::runOnFunction(Function &Fn) {
   bool Changed = false;
 
   // Initialize internal state.
   DT = &getAnalysis<DominatorTree>();
+  ExceptionValueVar = 0;
   F = &Fn;
 
   // Ensure that only unwind edges end at landing pads (a landing pad is a
@@ -656,6 +653,11 @@ bool DwarfEHPrepare::runOnFunction(Function &Fn) {
   // Move eh.exception calls to landing pads.
   Changed |= MoveExceptionValueCalls();
 
+  // Initialize any stack temporaries we introduced.
+  Changed |= FinishStackTemporaries();
+
+  // TODO: Turn any stack temporaries into registers if possible.
+
   Changed |= HandleURoRInvokes();
 
   LandingPads.clear();