MemDerefPrinter: Require DataLayoutPass for higher accuracy

[artagnon]

Summary

Without a valid data layout, deferenceable(N) doesn't get parsed or
propagated. Since this is the key item we are testing, add a dependency
on the pass.

[reames]

LGTM.

lib/Analysis/MemDerefPrinter.cpp

 //===- MemDerefPrinter.cpp - Printer for isDereferenceablePointer ---------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/Passes.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/Analysis/MemoryDependenceAnalysis.h"
 #include "llvm/IR/CallSite.h"
+#include "llvm/IR/DataLayout.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
 namespace {
   struct MemDerefPrinter : public FunctionPass {
     SmallVector<Value *, 4> Vec;
 
     static char ID; // Pass identifcation, replacement for typeid
     MemDerefPrinter() : FunctionPass(ID) {
       initializeMemDerefPrinterPass(*PassRegistry::getPassRegistry());
     }
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.addRequired<DataLayoutPass>();
+      AU.setPreservesAll();
+    }
     bool runOnFunction(Function &F) override;
     void print(raw_ostream &OS, const Module * = nullptr) const override;
     void releaseMemory() override {
       Vec.clear();
     }
   };
 }
 
 char MemDerefPrinter::ID = 0;
-INITIALIZE_PASS(MemDerefPrinter, "print-memderefs",
+INITIALIZE_PASS_BEGIN(MemDerefPrinter, "print-memderefs",
+                      "Memory Dereferenciblity of pointers in function", false, true)
+INITIALIZE_PASS_DEPENDENCY(DataLayoutPass)
+INITIALIZE_PASS_END(MemDerefPrinter, "print-memderefs",
                     "Memory Dereferenciblity of pointers in function", false, true)
 
 FunctionPass *llvm::createMemDerefPrinter() {
   return new MemDerefPrinter();
 }
 
 bool MemDerefPrinter::runOnFunction(Function &F) {
+  const DataLayout *DL = &getAnalysis<DataLayoutPass>().getDataLayout();
   for (auto &I: inst_range(F)) {
     if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
       Value *PO = LI->getPointerOperand();
-      if (PO->isDereferenceablePointer(nullptr))
+      if (PO->isDereferenceablePointer(DL))
         Vec.push_back(PO);
     }
   }
   return false;
 }
 
 void MemDerefPrinter::print(raw_ostream &OS, const Module *M) const {
   OS << "The following are dereferenceable:\n";
   for (auto &V: Vec) {
     V->print(OS);
     OS << "\n\n";
   }
 }

test/Analysis/ValueTracking/memory-dereferenceable.ll

 ; RUN: opt -print-memderefs -analyze -S <%s | FileCheck %s
 
 ; Uses the print-deref (+ analyze to print) pass to run
 ; isDereferenceablePointer() on many load instruction operands
 
+target datalayout = "e"
+
 declare zeroext i1 @return_i1()
 
 @globalstr = global [6 x i8] c"hello\00"
 
-define void @test(i32 addrspace(1)* byval %dparam) {
+define void @test(i32 addrspace(1)* dereferenceable(8) %dparam) {
 ; CHECK: The following are dereferenceable:
 ; CHECK: %globalptr
 ; CHECK: %alloca
 ; CHECK: %dparam
 ; We haven't yet taught it to look through relocations
 ; CHECK-NOT: %relocate
 ; CHECK-NOT: %nparam
 entry: