commit dd3f3edafadc92d603920c3b96bf331d0c3a9341
author Reid Kleckner <reid@kleckner.net> Tue Nov 04 02:02:14 2014 +0000
committer Reid Kleckner <reid@kleckner.net> Tue Nov 04 02:02:14 2014 +0000
tree 7b6b949b65280988aca1887d1c7a330fec1c7124
parent 8f1632d5c1e32912365f5673d832e0e8c8080a89

Revert "Transforms: reapply SVN r219899"

This reverts commit r220811 and r220839. It made an incorrect change to
musttail handling.

llvm-svn: 221226

llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp

diff --git a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 8f6855e6a..6fe5e18 100644
--- a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -253,7 +253,12 @@
     return false;
   AllCallsAreTailCalls = true;
 
+  // The local stack holds all alloca instructions and all byval arguments.
   AllocaDerivedValueTracker Tracker;
+  for (Argument &Arg : F.args()) {
+    if (Arg.hasByValAttr())
+      Tracker.walk(&Arg);
+  }
   for (auto &BB : F) {
     for (auto &I : BB)
       if (AllocaInst *AI = dyn_cast<AllocaInst>(&I))
@@ -309,8 +314,9 @@
         for (auto &Arg : CI->arg_operands()) {
           if (isa<Constant>(Arg.getUser()))
             continue;
-          if (isa<Argument>(Arg.getUser()))
-            continue;
+          if (Argument *A = dyn_cast<Argument>(Arg.getUser()))
+            if (!A->hasByValAttr())
+              continue;
           SafeToTail = false;
           break;
         }

llvm/lib/Transforms/Utils/InlineFunction.cpp

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 112bdcb..a1e42bb 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -743,8 +743,7 @@
 static Value *HandleByValArgument(Value *Arg, Instruction *TheCall,
                                   const Function *CalledFunc,
                                   InlineFunctionInfo &IFI,
-                                  unsigned ByValAlignment,
-                                  bool &AddedNewAllocas) {
+                                  unsigned ByValAlignment) {
   PointerType *ArgTy = cast<PointerType>(Arg->getType());
   Type *AggTy = ArgTy->getElementType();
 
@@ -786,7 +785,6 @@
   
   // Uses of the argument in the function should use our new alloca
   // instead.
-  AddedNewAllocas = true;
   return NewAlloca;
 }
 
@@ -960,7 +958,6 @@
   SmallVector<ReturnInst*, 8> Returns;
   ClonedCodeInfo InlinedFunctionInfo;
   Function::iterator FirstNewBlock;
-  bool AddedNewAllocas = false;
 
   { // Scope to destroy VMap after cloning.
     ValueToValueMapTy VMap;
@@ -984,8 +981,7 @@
       // modify the struct.
       if (CS.isByValArgument(ArgNo)) {
         ActualArg = HandleByValArgument(ActualArg, TheCall, CalledFunc, IFI,
-                                        CalledFunc->getParamAlignment(ArgNo+1),
-                                        AddedNewAllocas);
+                                        CalledFunc->getParamAlignment(ArgNo+1));
         if (ActualArg != *AI)
           ByValInit.push_back(std::make_pair(ActualArg, (Value*) *AI));
       }
@@ -1100,18 +1096,9 @@
         //    f -> musttail g ->     tail f  ==>  f ->     tail f
         //    f ->          g -> musttail f  ==>  f ->          f
         //    f ->          g ->     tail f  ==>  f ->          f
-        //
-        // If an alloca was introduced in the frame due to a byval parameter
-        // being passed to a subsequent call, tail calls must have the tail
-        // stripped as they may not access variables in the caller's stack.
-        // A single alloca ripples through out as the alloca may be aliased by
-        // bitcasts or may escape and be mutated outside of the function.
         CallInst::TailCallKind ChildTCK = CI->getTailCallKind();
         ChildTCK = std::min(CallSiteTailKind, ChildTCK);
-        if (AddedNewAllocas)
-          CI->setTailCallKind(CallInst::TCK_None);
-        else
-          CI->setTailCallKind(ChildTCK);
+        CI->setTailCallKind(ChildTCK);
         InlinedMustTailCalls |= CI->isMustTailCall();
 
         // Calls inlined through a 'nounwind' call site should be marked