Assertion `loBit <= BitWidth && "loBit out of range"' failed with -O1

[dbabokin]

Bugzilla Link	33844
Resolution	FIXED
Resolved on	Jul 21, 2017 01:02
Version	trunk
OS	All
Blocks	#33196
CC	@dbabokin,@topperc,@zmodem,@RKSimon,@Vsevolod-Livinskij

Extended Description

clang trunk, rev308350, x86_64

cat f.cpp
int a;
long b;
struct {
char c : 29;
} d;
void e() {
d.c = ~0 + 483647 & (a < 0) + 2147483647 >> (b << ~0 + 24) + 8388639;
}

clang++ -O1 -o f.o -c f.cpp -w
clang-5.0: /home/dybaboki/llvm/llvm-trunk-20170718/include/llvm/ADT/APInt.h:1399: void llvm::APInt::setBits(unsigned int, unsigned int): Assertion `loBit <= BitWidth && "loBit out of range"' failed.
#​0 0x00000000013170df llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x13170df)
#​1 0x00000000013173e6 SignalHandler(int) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x13173e6)
#​2 0x00007f27d8cbb370 __restore_rt (/lib64/libpthread.so.0+0xf370)
#​3 0x00007f27d78b31d7 __GI_raise (/lib64/libc.so.6+0x351d7)
#​4 0x00007f27d78b48c8 __GI_abort (/lib64/libc.so.6+0x368c8)
#​5 0x00007f27d78ac146 __assert_fail_base (/lib64/libc.so.6+0x2e146)
#​6 0x00007f27d78ac1f2 (/lib64/libc.so.6+0x2e1f2)
#​7 0x00000000007e0478 llvm::APInt::setBits(unsigned int, unsigned int) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x7e0478)
#​8 0x00000000008291e7 foldMaskAndShiftToScale(llvm::SelectionDAG&, llvm::SDValue, unsigned long, llvm::SDValue, llvm::SDValue, (anonymous namespace)::X86ISelAddressMode&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x8291e7)
#​9 0x00000000008284ef (anonymous namespace)::X86DAGToDAGISel::matchAddressRecursively(llvm::SDValue, (anonymous namespace)::X86ISelAddressMode&, unsigned int) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x8284ef)
#​10 0x00000000008299f9 (anonymous namespace)::X86DAGToDAGISel::matchAdd(llvm::SDValue, (anonymous namespace)::X86ISelAddressMode&, unsigned int) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x8299f9)
#​11 0x00000000008278cd (anonymous namespace)::X86DAGToDAGISel::matchAddressRecursively(llvm::SDValue, (anonymous namespace)::X86ISelAddressMode&, unsigned int) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x8278cd)
#​12 0x0000000000825c13 (anonymous namespace)::X86DAGToDAGISel::matchAddress(llvm::SDValue, (anonymous namespace)::X86ISelAddressMode&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x825c13)
#​13 0x000000000082a59f (anonymous namespace)::X86DAGToDAGISel::selectLEAAddr(llvm::SDValue, llvm::SDValue&, llvm::SDValue&, llvm::SDValue&, llvm::SDValue&, llvm::SDValue&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x82a59f)
#​14 0x00000000008242c8 (anonymous namespace)::X86DAGToDAGISel::CheckComplexPattern(llvm::SDNode*, llvm::SDNode*, llvm::SDValue, unsigned int, llvm::SmallVectorImpl<std::pair<llvm::SDValue, llvm::SDNode*> >&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x8242c8)
#​15 0x0000000001a5023f llvm::SelectionDAGISel::SelectCodeCommon(llvm::SDNode*, unsigned char const*, unsigned int) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x1a5023f)
#​16 0x000000000081f196 (anonymous namespace)::X86DAGToDAGISel::Select(llvm::SDNode*) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x81f196)
#​17 0x0000000001a497da llvm::SelectionDAGISel::DoInstructionSelection() (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x1a497da)
#​18 0x0000000001a487f2 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x1a487f2)
#​19 0x0000000001a45fa3 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x1a45fa3)
#​20 0x0000000001a42b56 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x1a42b56)
#​21 0x000000000081af81 (anonymous namespace)::X86DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x81af81)
#​22 0x0000000000bd4f64 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0xbd4f64)
#​23 0x0000000000ecfb1f llvm::FPPassManager::runOnFunction(llvm::Function&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0xecfb1f)
#​24 0x0000000000ecfd73 llvm::FPPassManager::runOnModule(llvm::Module&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0xecfd73)
#​25 0x0000000000ed0266 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0xed0266)
#​26 0x0000000001487c2f clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::DataLayout const&, llvm::Module*, clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream, std::default_deletellvm::raw_pwrite_stream >) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x1487c2f)
#​27 0x0000000001b31162 clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x1b31162)
#​28 0x0000000001f96806 clang::ParseAST(clang::Sema&, bool, bool) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x1f96806)
#​29 0x00000000018093d8 clang::FrontendAction::Execute() (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x18093d8)
#​30 0x00000000017cdd31 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x17cdd31)
#​31 0x000000000188e797 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x188e797)
#​32 0x000000000077174f cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x77174f)
#​33 0x000000000076f4d6 main (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x76f4d6)
#​34 0x00007f27d789fb35 __libc_start_main (/lib64/libc.so.6+0x21b35)
#​35 0x000000000076c817 _start (/home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0+0x76c817)
Stack dump:

0. Program arguments: /home/dybaboki/llvm/bin-trunk-20170718/bin/clang-5.0 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -disable-free -main-file-name f.cpp -mrelocation-model static -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -momit-leaf-frame-pointer -dwarf-column-info -debugger-tuning=gdb -coverage-notes-file /home/dybaboki/yarpgen/yarpgen/test_run_july17_creduce/result/clang/compfail/S_1729113319/f.gcno -resource-dir /home/dybaboki/llvm/bin-trunk-20170718/lib/clang/5.0.0 -internal-isystem /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5 -internal-isystem /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/x86_64-redhat-linux -internal-isystem /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/backward -internal-isystem /usr/local/include -internal-isystem /home/dybaboki/llvm/bin-trunk-20170718/lib/clang/5.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -O1 -w -fdeprecated-macro -fdebug-compilation-dir /home/dybaboki/yarpgen/yarpgen/test_run_july17_creduce/result/clang/compfail/S_1729113319 -ferror-limit 19 -fmessage-length 272 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o f.o -x c++ f.cpp
1. parser at end of file
2. Code generation
3. Running pass 'Function Pass Manager' on module 'f.cpp'.
4. Running pass 'X86 DAG->DAG Instruction Selection' on function '@_Z1ev'
   clang-5.0: error: unable to execute command: Aborted
   clang-5.0: error: clang frontend command failed due to signal (use -v to see invocation)
   clang version 5.0.0 (trunk 308350)
   Target: x86_64-unknown-linux-gnu
   Thread model: posix
   InstalledDir: /home/dybaboki/llvm/bin-trunk-20170718/bin
   clang-5.0: note: diagnostic msg: PLEASE submit a bug report to http://llvm.org/bugs/ and include the crash backtrace, preprocessed source, and associated run script.
   clang-5.0: note: diagnostic msg:

---

[llvmbot]

Reduced:

target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

@​global = external global i32
@​global.1 = external global i64

define void @​patatino() {
bb:
%tmp = load i32, i32* @​global
%tmp1 = lshr i32 %tmp, 31
%tmp2 = add nuw nsw i32 %tmp1, 2147483647
%tmp3 = load i64, i64* @​global.1
%tmp4 = shl i64 %tmp3, 23
%tmp5 = add nsw i64 %tmp4, 8388639
%tmp6 = trunc i64 %tmp5 to i32
%tmp7 = lshr i32 %tmp2, %tmp6
%tmp8 = load i32, i32* @​global
%tmp9 = and i32 %tmp7, 62
%tmp10 = and i32 %tmp8, -536870912
%tmp11 = or i32 %tmp9, %tmp10
store i32 %tmp11, i32* @​global
ret void
}

[llvmbot]

The issue here is in foldMaskAndShiftToScale().
MaskLZ is 58 before:

// Scale the leading zero count down based on the actual size of the value.
// Also scale it down based on the size of the shift.
MaskLZ -= (64 - X.getSimpleValueType().getSizeInBits()) + ShiftAmt;

The RHS quantity is 63, so we end up with:

MaskLZ = 4294967291

Boom.

Proposed patch:

$ git diff
diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 3c4589a..8f24f98 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1055,7 +1055,10 @@ static bool foldMaskAndShiftToScale(SelectionDAG &DAG, SDValue N,

// Scale the leading zero count down based on the actual size of the value.
// Also scale it down based on the size of the shift.

• MaskLZ -= (64 - X.getSimpleValueType().getSizeInBits()) + ShiftAmt;

• unsigned ScaleDown = (64 - X.getSimpleValueType().getSizeInBits()) + ShiftAmt;

• if (MaskLZ < ScaleDown)

• return true;

• MaskLZ -= ScaleDown;

  // The final check is to ensure that any masked out high bits of X are
  // already known to be zero. Otherwise, the mask has a semantic impact

Craig/Simon, what do you think?

[llvmbot]

Briefly discussed offline with Simon and he was OK with that.
I'll open a separate bug for the backport.

[llvmbot]

r308503

[zmodem]

Merged in r308718.

[zmodem]

mentioned in issue #33196