Rebased PNaCl localmods in LLVM to 223109

lib/Transforms/NaCl/RewriteLLVMIntrinsics.cpp

+//===- RewriteLLVMIntrinsics.cpp - Rewrite LLVM intrinsics to other values ===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass replaces calls to LLVM intrinsics that are *not* part of the
+// PNaCl stable bitcode ABI into simpler values.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/Twine.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/NaCl.h"
+#include <string>
+
+using namespace llvm;
+
+namespace {
+class RewriteLLVMIntrinsics : public ModulePass {
+public:
+  static char ID;
+  RewriteLLVMIntrinsics() : ModulePass(ID) {
+    // This is a module pass because this makes it easier to access uses
+    // of global intrinsic functions.
+    initializeRewriteLLVMIntrinsicsPass(*PassRegistry::getPassRegistry());
+  }
+
+  virtual bool runOnModule(Module &M);
+
+  /// Rewrite an intrinsic to something different.
+  class IntrinsicRewriter {
+  public:
+    Function *function() const { return F; }
+    /// Called once per \p Call of the Intrinsic Function.
+    void rewriteCall(CallInst *Call) { doRewriteCall(Call); }
+
+  protected:
+    IntrinsicRewriter(Module &M, Intrinsic::ID IntrinsicID)
+        : F(Intrinsic::getDeclaration(&M, IntrinsicID)) {}
+    virtual ~IntrinsicRewriter() {}
+    /// This pure virtual method must be defined by implementors, and
+    /// will be called by rewriteCall.
+    virtual void doRewriteCall(CallInst *Call) = 0;
+
+    Function *F;
+
+  private:
+    IntrinsicRewriter() LLVM_DELETED_FUNCTION;
+    IntrinsicRewriter(const IntrinsicRewriter &) LLVM_DELETED_FUNCTION;
+    IntrinsicRewriter &operator=(
+        const IntrinsicRewriter &) LLVM_DELETED_FUNCTION;
+  };
+
+private:
+  /// Visit all uses of a Function, rewrite it using the \p Rewriter,
+  /// and then delete the Call. Later delete the Function from the
+  /// Module. Returns true if the Module was changed.
+  bool visitUses(IntrinsicRewriter &Rewriter);
+};
+
+/// Rewrite a Call to nothing.
+class ToNothing : public RewriteLLVMIntrinsics::IntrinsicRewriter {
+public:
+  ToNothing(Module &M, Intrinsic::ID IntrinsicID)
+      : IntrinsicRewriter(M, IntrinsicID) {}
+  virtual ~ToNothing() {}
+
+protected:
+  virtual void doRewriteCall(CallInst *Call) {
+    // Nothing to do: the visit does the deletion.
+  }
+};
+
+/// Rewrite a Call to a ConstantInt of the same type.
+class ToConstantInt : public RewriteLLVMIntrinsics::IntrinsicRewriter {
+public:
+  ToConstantInt(Module &M, Intrinsic::ID IntrinsicID, uint64_t Value)
+      : IntrinsicRewriter(M, IntrinsicID), Value(Value),
+        RetType(function()->getFunctionType()->getReturnType()) {}
+  virtual ~ToConstantInt() {}
+
+protected:
+  virtual void doRewriteCall(CallInst *Call) {
+    Constant *C = ConstantInt::get(RetType, Value);
+    Call->replaceAllUsesWith(C);
+  }
+
+private:
+  uint64_t Value;
+  Type *RetType;
+};
+}
+
+char RewriteLLVMIntrinsics::ID = 0;
+INITIALIZE_PASS(RewriteLLVMIntrinsics, "rewrite-llvm-intrinsic-calls",
+                "Rewrite LLVM intrinsic calls to simpler expressions", false,
+                false)
+
+bool RewriteLLVMIntrinsics::runOnModule(Module &M) {
+  // Replace all uses of the @llvm.flt.rounds intrinsic with the constant
+  // "1" (round-to-nearest). Until we add a second intrinsic like
+  // @llvm.set.flt.round it is impossible to have a rounding mode that is
+  // not the initial rounding mode (round-to-nearest). We can remove
+  // this rewrite after adding a set() intrinsic.
+  ToConstantInt FltRoundsRewriter(M, Intrinsic::flt_rounds, 1);
+
+  // Remove all @llvm.prefetch intrinsics.
+  ToNothing PrefetchRewriter(M, Intrinsic::prefetch);
+
+  return visitUses(FltRoundsRewriter) | visitUses(PrefetchRewriter);
+}
+
+bool RewriteLLVMIntrinsics::visitUses(IntrinsicRewriter &Rewriter) {
+  Function *F = Rewriter.function();
+  SmallVector<CallInst *, 64> Calls;
+  for (User *U : F->users()) {
+    if (CallInst *Call = dyn_cast<CallInst>(U)) {
+      Calls.push_back(Call);
+    } else {
+      // Intrinsics we care about currently don't need to handle this case.
+      std::string S;
+      raw_string_ostream OS(S);
+      OS << "Taking the address of this intrinsic is invalid: " << *U;
+      report_fatal_error(OS.str());
+    }
+  }
+
+  for (auto Call : Calls) {
+      Rewriter.rewriteCall(Call);
+      Call->eraseFromParent();
+  }
+
+  F->eraseFromParent();
+  return !Calls.empty();
+}
+
+ModulePass *llvm::createRewriteLLVMIntrinsicsPass() {
+  return new RewriteLLVMIntrinsics();
+}