[Evaluator] Improve evaluation of call instruction

Differential revision: https://reviews.llvm.org/D46584

llvm-svn: 335324

1 files changed, 30 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/Evaluator.cpp b/llvm/lib/Transforms/Utils/Evaluator.cpp
index 9440ae3ef2a..3f9daa2d29a 100644
--- a/llvm/lib/Transforms/Utils/Evaluator.cpp
+++ b/llvm/lib/Transforms/Utils/Evaluator.cpp
@@ -217,6 +217,33 @@ Constant *Evaluator::ComputeLoadResult(Constant *P) {
   return nullptr;  // don't know how to evaluate.
 }
 
+Function *Evaluator::getCallee(Value *V) {
+  auto *CE = dyn_cast<ConstantExpr>(V);
+  if (!CE)
+    return dyn_cast<Function>(getVal(V));
+
+  Constant *C =
+      CE->getOpcode() == Instruction::BitCast
+          ? ConstantFoldLoadThroughBitcast(CE, CE->getOperand(0)->getType(), DL)
+          : CE;
+  return dyn_cast<Function>(C);
+}
+
+/// If call expression contains bitcast then we may need to cast
+/// evaluated return value to a type of the call expression.
+Constant *Evaluator::castCallResultIfNeeded(Value *CallExpr, Constant *RV) {
+  ConstantExpr *CE = dyn_cast<ConstantExpr>(CallExpr);
+  if (!CE || CE->getOpcode() != Instruction::BitCast)
+    return RV;
+
+  if (auto *FT =
+          dyn_cast<FunctionType>(CE->getType()->getPointerElementType())) {
+    RV = ConstantFoldLoadThroughBitcast(RV, FT->getReturnType(), DL);
+    assert(RV && "Failed to fold bitcast call expr");
+  }
+  return RV;
+}
+
 /// Evaluate all instructions in block BB, returning true if successful, false
 /// if we can't evaluate it.  NewBB returns the next BB that control flows into,
 /// or null upon return.
@@ -465,7 +492,7 @@ bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
       }
 
       // Resolve function pointers.
-      Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue()));
+      Function *Callee = getCallee(CS.getCalledValue());
       if (!Callee || Callee->isInterposable()) {
         LLVM_DEBUG(dbgs() << "Can not resolve function pointer.\n");
         return false;  // Cannot resolve.
@@ -478,7 +505,7 @@ bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
       if (Callee->isDeclaration()) {
         // If this is a function we can constant fold, do it.
         if (Constant *C = ConstantFoldCall(CS, Callee, Formals, TLI)) {
-          InstResult = C;
+          InstResult = castCallResultIfNeeded(CS.getCalledValue(), C);
           LLVM_DEBUG(dbgs() << "Constant folded function call. Result: "
                             << *InstResult << "\n");
         } else {
@@ -499,7 +526,7 @@ bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
           return false;
         }
         ValueStack.pop_back();
-        InstResult = RetVal;
+        InstResult = castCallResultIfNeeded(CS.getCalledValue(), RetVal);
 
         if (InstResult) {
           LLVM_DEBUG(dbgs() << "Successfully evaluated function. Result: "