Make TypeBasedAliasAnalysis default to doing nothing, with a command-line

option to enable it.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116722 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/TypeBasedAliasAnalysis.cpp

@@ -32,8 +32,12 @@
 #include "llvm/Module.h"
 #include "llvm/Metadata.h"
 #include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
 using namespace llvm;
 
+// For testing purposes, enable TBAA only via a special option.
+static cl::opt<bool> EnableTBAA("enable-tbaa");
+
 namespace {
   /// TBAANode - This is a simple wrapper around an MDNode which provides a
   /// higher-level interface by hiding the details of how alias analysis
@@ -122,6 +126,9 @@ TypeBasedAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
 AliasAnalysis::AliasResult
 TypeBasedAliasAnalysis::alias(const Location &LocA,
                               const Location &LocB) {
+  if (!EnableTBAA)
+    return AliasAnalysis::alias(LocA, LocB);
+
   // Get the attached MDNodes. If either value lacks a tbaa MDNode, we must
   // be conservative.
   const MDNode *AM = LocA.TBAATag;
@@ -168,6 +175,9 @@ TypeBasedAliasAnalysis::alias(const Location &LocA,
 }
 
 bool TypeBasedAliasAnalysis::pointsToConstantMemory(const Location &Loc) {
+  if (!EnableTBAA)
+    return AliasAnalysis::pointsToConstantMemory(Loc);
+
   const MDNode *M = Loc.TBAATag;
   if (!M) return false;
 

test/Analysis/TypeBasedAliasAnalysis/aliastest.ll

@@ -1,4 +1,4 @@
-; RUN: opt < %s -basicaa -tbaa -gvn -S | FileCheck %s
+; RUN: opt < %s -enable-tbaa -basicaa -tbaa -gvn -S | FileCheck %s
 
 ; CHECK: @test0_yes
 ; CHECK: add i8 %x, %x