Re-apply "Introduce FuzzMutate library"

Same as r311392 with some fixes for library dependencies. Thanks to
Chapuni for helping work those out!

Original commit message:

This introduces the FuzzMutate library, which provides structured
fuzzing for LLVM IR, as described in my EuroLLVM 2017 talk. Most of
the basic mutators to inject and delete IR are provided, with support
for most basic operations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311402 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 38 insertions, 0 deletions

diff --git a/lib/FuzzMutate/OpDescriptor.cpp b/lib/FuzzMutate/OpDescriptor.cpp
new file mode 100644
index 00000000000..1c5d8f606ae
--- /dev/null
+++ b/lib/FuzzMutate/OpDescriptor.cpp
@@ -0,0 +1,38 @@
+//===-- OpDescriptor.cpp --------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/FuzzMutate/OpDescriptor.h"
+#include "llvm/IR/Constants.h"
+
+using namespace llvm;
+using namespace fuzzerop;
+
+void fuzzerop::makeConstantsWithType(Type *T, std::vector<Constant *> &Cs) {
+  if (auto *IntTy = dyn_cast<IntegerType>(T)) {
+    uint64_t W = IntTy->getBitWidth();
+    Cs.push_back(ConstantInt::get(IntTy, APInt::getMaxValue(W)));
+    Cs.push_back(ConstantInt::get(IntTy, APInt::getMinValue(W)));
+    Cs.push_back(ConstantInt::get(IntTy, APInt::getSignedMaxValue(W)));
+    Cs.push_back(ConstantInt::get(IntTy, APInt::getSignedMinValue(W)));
+    Cs.push_back(ConstantInt::get(IntTy, APInt::getOneBitSet(W, W / 2)));
+  } else if (T->isFloatingPointTy()) {
+    auto &Ctx = T->getContext();
+    auto &Sem = T->getFltSemantics();
+    Cs.push_back(ConstantFP::get(Ctx, APFloat::getZero(Sem)));
+    Cs.push_back(ConstantFP::get(Ctx, APFloat::getLargest(Sem)));
+    Cs.push_back(ConstantFP::get(Ctx, APFloat::getSmallest(Sem)));
+  } else
+    Cs.push_back(UndefValue::get(T));
+}
+
+std::vector<Constant *> fuzzerop::makeConstantsWithType(Type *T) {
+  std::vector<Constant *> Result;
+  makeConstantsWithType(T, Result);
+  return Result;
+}