[llvm] r272616 - Fix for (benign) uninitialized read caught by UBSan bot.

[Sean Silva via llvm-commits]

Author: silvas
Date: Mon Jun 13 21:45:01 2016
New Revision: 272616

URL: http://llvm.org/viewvc/llvm-project?rev=272616&view=rev
Log:
Fix for (benign) uninitialized read caught by UBSan bot.

What happened here is that in the new PM there is a bunch of new copying
(actually, moving) and so this reads the HasProfileData member in
situations where it used to not be read.
It used to only be read strictly in the "runOnFunction" method and its
callees, where is *is* initialized (even after my patch).
So this ends up being benign as far as functional behavior of the
compiler (since we set HasProfileData in the "runImpl" method before we
ever make decisions based on it).

It's awesome that UBSan caught this. It highlights one more thing to
watch out for when porting passes.

Sanitizer bot log was:

-- Testing: 17049 tests, 32 threads --
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80..
FAIL: LLVM :: Transforms/JumpThreading/thread-loads.ll (15184 of 17049)
******************** TEST 'LLVM :: Transforms/JumpThreading/thread-loads.ll' FAILED ********************
Script:
--
/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/./bin/opt < /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/test/Transforms/JumpThreading/thread-loads.ll -jump-threading -S | /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/./bin/FileCheck /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/test/Transforms/JumpThreading/thread-loads.ll
/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/./bin/opt < /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/test/Transforms/JumpThreading/thread-loads.ll -passes=jump-threading -S | /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/./bin/FileCheck /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/test/Transforms/JumpThreading/thread-loads.ll
--
Exit Code: 2

Command Output (stderr):
--
/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/include/llvm/Transforms/Scalar/JumpThreading.h:90:57: runtime error: load of value 136, which is not a valid value for type 'bool'
    #0 0x2c33ba1 in llvm::JumpThreadingPass::JumpThreadingPass(llvm::JumpThreadingPass&&) /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/include/llvm/Transforms/Scalar/JumpThreading.h:90:57
    #1 0x2bc88e4 in void llvm::PassManager<llvm::Function>::addPass<llvm::JumpThreadingPass>(llvm::JumpThreadingPass) /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/include/llvm/IR/PassManager.h:282:40
    #2 0x2bb2682 in llvm::PassBuilder::parseFunctionPassName(llvm::PassManager<llvm::Function>&, llvm::StringRef) /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/lib/Passes/PassRegistry.def:133:1
    #3 0x2bb4914 in llvm::PassBuilder::parseFunctionPassPipeline(llvm::PassManager<llvm::Function>&, llvm::StringRef&, bool, bool) /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/lib/Passes/PassBuilder.cpp:489:12
    #4 0x2bb6f81 in llvm::PassBuilder::parsePassPipeline(llvm::PassManager<llvm::Module>&, llvm::StringRef, bool, bool) /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/lib/Passes/PassBuilder.cpp:674:10
    #5 0x986690 in llvm::runPassPipeline(llvm::StringRef, llvm::LLVMContext&, llvm::Module&, llvm::TargetMachine*, llvm::tool_output_file*, llvm::StringRef, llvm::opt_tool::OutputKind, llvm::opt_tool::VerifierKind, bool, bool) /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/tools/opt/NewPMDriver.cpp:85:8
    #6 0x9af25e in main /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/tools/opt/opt.cpp:468:12
    #7 0x7fd7e27dbf44 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21f44)
    #8 0x960157 in _start (/mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/bin/opt+0x960157)

FileCheck error: '-' is empty.
FileCheck command line:  /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/./bin/FileCheck /mnt/b/sanitizer-buildbot3/sanitizer-x86_64-linux-fast/build/llvm/test/Transforms/JumpThreading/thread-loads.ll

--

********************
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
Testing Time: 128.90s
********************
Failing Tests (1):
    LLVM :: Transforms/JumpThreading/thread-loads.ll

  Expected Passes    : 16725
  Expected Failures  : 129
  Unsupported Tests  : 194
  Unexpected Failures: 1

Modified:
    llvm/trunk/include/llvm/Transforms/Scalar/JumpThreading.h

Modified: llvm/trunk/include/llvm/Transforms/Scalar/JumpThreading.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Scalar/JumpThreading.h?rev=272616&r1=272615&r2=272616&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Scalar/JumpThreading.h (original)
+++ llvm/trunk/include/llvm/Transforms/Scalar/JumpThreading.h Mon Jun 13 21:45:01 2016
@@ -61,7 +61,7 @@ class JumpThreadingPass : public PassInf
   LazyValueInfo *LVI;
   std::unique_ptr<BlockFrequencyInfo> BFI;
   std::unique_ptr<BranchProbabilityInfo> BPI;
-  bool HasProfileData;
+  bool HasProfileData = false;
 #ifdef NDEBUG
   SmallPtrSet<const BasicBlock *, 16> LoopHeaders;
 #else