[Evaluator] Improve evaluation of call instruction

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

llvm-svn: 335324

4 files changed, 143 insertions, 3 deletions

diff --git a/llvm/include/llvm/Transforms/Utils/Evaluator.h b/llvm/include/llvm/Transforms/Utils/Evaluator.h
index 0e987b93177..35d8d376d62 100644
--- a/llvm/include/llvm/Transforms/Utils/Evaluator.h
+++ b/llvm/include/llvm/Transforms/Utils/Evaluator.h
@@ -73,6 +73,12 @@ public:
     ValueStack.back()[V] = C;
   }
 
+  Function *getCallee(Value *V);
+
+  /// Given call expression and result value cast the result value
+  /// to call expression type if call expression contains bitcast.
+  Constant *castCallResultIfNeeded(Value *CallExpr, Constant *RV);
+
   const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
     return MutatedMemory;
   }
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: "
diff --git a/llvm/test/Transforms/GlobalOpt/evaluate-call.ll b/llvm/test/Transforms/GlobalOpt/evaluate-call.ll
new file mode 100644
index 00000000000..7a7df598e8c
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/evaluate-call.ll
@@ -0,0 +1,52 @@
+; Checks if bitcasted call expression can be evaluated
+; Given call expresion:
+;   %struct.Foo* bitcast (%struct.Bar* ()* @_Z6getFoov to %struct.Foo* ()*)()
+; We evaluate call to function _Z6getFoov and then cast the result to %structFoo*
+
+; RUN: opt -globalopt -instcombine %s -S -o - | FileCheck %s
+
+; CHECK:      i32 @main()
+; CHECK-NEXT:   %1 = load i64, i64* inttoptr (i64 32 to i64*), align 32
+; CHECK-NEXT:   %2 = trunc i64 %1 to i32
+; CHECK-NEXT:   ret i32 %2
+; CHECK-NOT: _GLOBAL__sub_I_main
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux-gnu"
+
+%struct.Bar = type { i64, i64 }
+%struct.S = type { %struct.Foo* }
+%struct.Foo = type { i64, i64 }
+%struct.Baz = type { i64, i64, %struct.Bar }
+
+@instance = internal local_unnamed_addr global %struct.S zeroinitializer, align 8
+@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_main.cpp, i8* null }]
+@gBaz = available_externally dso_local local_unnamed_addr global %struct.Baz* null, align 8
+@gFoo = available_externally dso_local local_unnamed_addr global %struct.Bar* null, align 8
+
+; Function Attrs: norecurse nounwind readonly uwtable
+define dso_local i32 @main() local_unnamed_addr {
+  %1 = load %struct.Foo*, %struct.Foo** getelementptr inbounds (%struct.S, %struct.S* @instance, i64 0, i32 0), align 8
+  %2 = getelementptr inbounds %struct.Foo, %struct.Foo* %1, i64 0, i32 0
+  %3 = load i64, i64* %2, align 8
+  %4 = trunc i64 %3 to i32
+  ret i32 %4
+}
+
+; Function Attrs: uwtable
+define internal void @_GLOBAL__sub_I_main.cpp() section ".text.startup" {
+  %1 = tail call %struct.Foo* bitcast (%struct.Bar* ()* @_Z6getFoov to %struct.Foo* ()*)()
+  %2 = getelementptr inbounds %struct.Foo, %struct.Foo* %1, i64 1
+  store %struct.Foo* %2, %struct.Foo** getelementptr inbounds (%struct.S, %struct.S* @instance, i64 0, i32 0), align 8
+  ret void
+}
+
+; Function Attrs: norecurse nounwind readonly uwtable
+define available_externally dso_local %struct.Bar* @_Z6getFoov() local_unnamed_addr {
+  %1 = load %struct.Bar*, %struct.Bar** @gFoo, align 8
+  %2 = icmp eq %struct.Bar* %1, null
+  %3 = load %struct.Baz*, %struct.Baz** @gBaz, align 8
+  %4 = getelementptr inbounds %struct.Baz, %struct.Baz* %3, i64 0, i32 2
+  %5 = select i1 %2, %struct.Bar* %4, %struct.Bar* %1
+  ret %struct.Bar* %5
+}
diff --git a/llvm/test/Transforms/GlobalOpt/evaluate-constfold-call.ll b/llvm/test/Transforms/GlobalOpt/evaluate-constfold-call.ll
new file mode 100644
index 00000000000..8ec001e9d82
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/evaluate-constfold-call.ll
@@ -0,0 +1,55 @@
+; Check if we can evaluate a bitcasted call to a function which is constant folded.
+; Evaluator folds call to fmodf, replacing it with constant value in case both operands
+; are known at compile time.
+; RUN: opt -globalopt -instcombine %s -S -o - | FileCheck %s
+
+; CHECK:      @_q = dso_local local_unnamed_addr global %struct.Q { i32 1066527622 }
+; CHECK:      define dso_local i32 @main
+; CHECK-NEXT:   %[[V:.+]] = load i32, i32* getelementptr inbounds (%struct.Q, %struct.Q* @_q, i64 0, i32 0), align 4
+; CHECK-NEXT:   ret i32 %[[V]]
+
+source_filename = "main.cpp"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-none-linux-gnu"
+
+%struct.Q = type { i32 }
+
+$_ZN1QC2Ev = comdat any
+
+@_q = dso_local global %struct.Q zeroinitializer, align 4
+@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_main.cpp, i8* null }]
+
+define internal void @__cxx_global_var_init() section ".text.startup" {
+  call void @_ZN1QC2Ev(%struct.Q* @_q)
+  ret void
+}
+
+define linkonce_odr dso_local void @_ZN1QC2Ev(%struct.Q*) unnamed_addr #1 comdat align 2 {
+  %2 = alloca %struct.Q*, align 8
+  store %struct.Q* %0, %struct.Q** %2, align 8
+  %3 = load %struct.Q*, %struct.Q** %2, align 8
+  %4 = getelementptr inbounds %struct.Q, %struct.Q* %3, i32 0, i32 0
+  %5 = call i32 bitcast (float (float, float)* @fmodf to i32 (float, float)*)(float 0x40091EB860000000, float 2.000000e+00)
+  store i32 %5, i32* %4, align 4
+  ret void
+}
+
+define dso_local i32 @main(i32, i8**) {
+  %3 = alloca i32, align 4
+  %4 = alloca i32, align 4
+  %5 = alloca i8**, align 8
+  store i32 0, i32* %3, align 4
+  store i32 %0, i32* %4, align 4
+  store i8** %1, i8*** %5, align 8
+  %6 = load i32, i32* getelementptr inbounds (%struct.Q, %struct.Q* @_q, i32 0, i32 0), align 4
+  ret i32 %6
+}
+
+; Function Attrs: nounwind
+declare dso_local float @fmodf(float, float)
+
+; Function Attrs: noinline uwtable
+define internal void @_GLOBAL__sub_I_main.cpp() section ".text.startup" {
+  call void @__cxx_global_var_init()
+  ret void
+}