Remove prefetch

Following our discussion in the related bug, prefetch will not be part of our initial stable ABI.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3531
TEST= cd ./pnacl/build/llvm_x86_64; ninja check
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/19771015

2 files changed, 98 insertions, 26 deletions

diff --git a/lib/Analysis/NaCl/PNaClABIVerifyModule.cpp b/lib/Analysis/NaCl/PNaClABIVerifyModule.cpp
index a418246bae..2793d2ec96 100644
--- a/lib/Analysis/NaCl/PNaClABIVerifyModule.cpp
+++ b/lib/Analysis/NaCl/PNaClABIVerifyModule.cpp
@@ -316,7 +316,6 @@ bool AllowedIntrinsics::isAllowed(const Function *Func) {
     case Intrinsic::dbg_value:
       return PNaClABIAllowDevIntrinsics || PNaClABIAllowDebugMetadata;
     case Intrinsic::nacl_target_arch: // Used by translator self-build.
-    case Intrinsic::prefetch: // TODO(jfb): Use our own data-prefetch intrinsic instead.
       return PNaClABIAllowDevIntrinsics;
   }
 }
diff --git a/lib/Transforms/NaCl/RewriteLLVMIntrinsics.cpp b/lib/Transforms/NaCl/RewriteLLVMIntrinsics.cpp
index 17cd2347cc..9b3d3cea51 100644
--- a/lib/Transforms/NaCl/RewriteLLVMIntrinsics.cpp
+++ b/lib/Transforms/NaCl/RewriteLLVMIntrinsics.cpp
@@ -12,57 +12,130 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/Twine.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 {
+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:
-    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());
-    }
+    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;
 
-    virtual bool runOnModule(Module &M);
+    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)
+                "Rewrite LLVM intrinsic calls to simpler expressions", false,
+                false)
 
 bool RewriteLLVMIntrinsics::runOnModule(Module &M) {
-  bool Changed = false;
+  // 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);
 
-  // Iterate over all uses of the llvm.flt.rounds, and replace it 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.
-  Function *FltRounds = Intrinsic::getDeclaration(&M, Intrinsic::flt_rounds);
-  Type *RetType = FltRounds->getFunctionType()->getReturnType();
-  for (Value::use_iterator UI = FltRounds->use_begin(),
-           UE = FltRounds->use_end(); UI != UE;) {
+  // Remove all @llvm.prefetch intrinsics.
+  ToNothing PrefetchRewriter(M, Intrinsic::prefetch);
+
+  return visitUses(FltRoundsRewriter) | visitUses(PrefetchRewriter);
+}
+
+bool RewriteLLVMIntrinsics::visitUses(IntrinsicRewriter &Rewriter) {
+  bool Changed = false;
+  Function *F = Rewriter.function();
+  for (Value::use_iterator UI = F->use_begin(), UE = F->use_end(); UI != UE;) {
     Value *Use = *UI++;
     if (CallInst *Call = dyn_cast<CallInst>(Use)) {
-      Constant *C = ConstantInt::get(RetType, 1);
-      Call->replaceAllUsesWith(C);
+      Rewriter.rewriteCall(Call);
       Call->eraseFromParent();
       Changed = true;
     } else {
-      report_fatal_error("Taking the address of llvm.flt.rounds is invalid");
+      // 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: " << *Use;
+      report_fatal_error(OS.str());
     }
   }
-  FltRounds->eraseFromParent();
-
+  F->eraseFromParent();
   return Changed;
 }