Merging r257645:

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r257645 | dim | 2016-01-13 19:29:46 +0100 (Wed, 13 Jan 2016) | 22 lines

Avoid undefined behavior in LinkAllPasses.h

The LinkAllPasses.h file is included in several main programs, to force
a large number of passes to be linked in.  However, the ForcePassLinking
constructor uses undefined behavior, since it calls member functions on
`nullptr`, e.g.:

      ((llvm::Function*)nullptr)->viewCFGOnly();
      llvm::RGPassManager RGM;
      ((llvm::RegionPass*)nullptr)->runOnRegion((llvm::Region*)nullptr, RGM);

When the optimization level is -O2 or higher, the code below the first
nullptr dereference is optimized away, and replaced by `ud2` (on x86).

Therefore, the calls after that first dereference are never emitted.  In
my case, I noticed there was no call to `llvm::sys::RunningOnValgrind()`!

Replace instances of dereferencing `nullptr` with either objects on the
stack, or regular function calls.

Differential Revision: http://reviews.llvm.org/D15996

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_38@257660 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/LinkAllPasses.h b/include/llvm/LinkAllPasses.h
index d695d11a63697a13a590b6cd665a9653b8483e78..327faac33206709e88a8abe5e773c655a20f713f 100644 (file)
--- a/include/llvm/LinkAllPasses.h
+++ b/include/llvm/LinkAllPasses.h
@@ -160,9 +160,11 @@ namespace {
       (void) llvm::createPostOrderFunctionAttrsPass();
       (void) llvm::createReversePostOrderFunctionAttrsPass();
       (void) llvm::createMergeFunctionsPass();
-      (void) llvm::createPrintModulePass(*(llvm::raw_ostream*)nullptr);
-      (void) llvm::createPrintFunctionPass(*(llvm::raw_ostream*)nullptr);
-      (void) llvm::createPrintBasicBlockPass(*(llvm::raw_ostream*)nullptr);
+      std::string buf;
+      llvm::raw_string_ostream os(buf);
+      (void) llvm::createPrintModulePass(os);
+      (void) llvm::createPrintFunctionPass(os);
+      (void) llvm::createPrintBasicBlockPass(os);
       (void) llvm::createModuleDebugInfoPrinterPass();
       (void) llvm::createPartialInliningPass();
       (void) llvm::createLintPass();
@@ -186,10 +188,10 @@ namespace {
 
       (void)new llvm::IntervalPartition();
       (void)new llvm::ScalarEvolutionWrapperPass();
-      ((llvm::Function*)nullptr)->viewCFGOnly();
+      llvm::Function::Create(nullptr, llvm::GlobalValue::ExternalLinkage)->viewCFGOnly();
       llvm::RGPassManager RGM;
-      ((llvm::RegionPass*)nullptr)->runOnRegion((llvm::Region*)nullptr, RGM);
-      llvm::AliasSetTracker X(*(llvm::AliasAnalysis*)nullptr);
+      llvm::AliasAnalysis AA;
+      llvm::AliasSetTracker X(AA);
       X.add(nullptr, 0, llvm::AAMDNodes()); // for -print-alias-sets
       (void) llvm::AreStatisticsEnabled();
       (void) llvm::sys::RunningOnValgrind();