[AsmPrinter] Global Constant with Big Endian crashes backend with assertion ShiftAmt <= BitWidth && "Invalid shift amount" failed

[HazyFish]

Description

When targeting aarch64_be, the following code crashes the backend with error ShiftAmt <= BitWidth && "Invalid shift amount".

This does not occur when targeting aarch64.

Minimal Reproduction

https://godbolt.org/z/sf17n5Me6

Code

@G = global <4 x i1> <i1 true, i1 false, i1 true, i1 true>

Stack Trace

llc: /home/henry/aflplusplus-isel/llvm-project/llvm/include/llvm/ADT/APInt.h:840: void llvm::APInt::lshrInPlace(unsigned int): Assertion `ShiftAmt <= BitWidth && "Invalid shift amount"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /home/henry/aflplusplus-isel/llvm-project/build-debug/bin/llc -mtriple=aarch64_be ./crash-reports/dagisel-aarch64_be/1.ll
 #0 0x00000000047c438a llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/Support/Unix/Signals.inc:569:11
 #1 0x00000000047c453b PrintStackTraceSignalHandler(void*) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/Support/Unix/Signals.inc:636:1
 #2 0x00000000047c2b76 llvm::sys::RunSignalHandlers() /home/henry/aflplusplus-isel/llvm-project/llvm/lib/Support/Signals.cpp:104:5
 #3 0x00000000047c4c65 SignalHandler(int) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/Support/Unix/Signals.inc:407:1
 #4 0x00007f37d8ff5980 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12980)
 #5 0x00007f37d7ee5e87 raise /build/glibc-CVJwZb/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #6 0x00007f37d7ee77f1 abort /build/glibc-CVJwZb/glibc-2.27/stdlib/abort.c:81:0
 #7 0x00007f37d7ed73fa __assert_fail_base /build/glibc-CVJwZb/glibc-2.27/assert/assert.c:89:0
 #8 0x00007f37d7ed7472 (/lib/x86_64-linux-gnu/libc.so.6+0x30472)
 #9 0x0000000000db84e6 llvm::APInt::lshrInPlace(unsigned int) /home/henry/aflplusplus-isel/llvm-project/llvm/include/llvm/ADT/APInt.h:0:5
#10 0x00000000031b908a emitGlobalConstantLargeInt(llvm::ConstantInt const*, llvm::AsmPrinter&) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:3272:5
#11 0x00000000031b9bba emitGlobalConstantVector(llvm::DataLayout const&, llvm::ConstantVector const*, llvm::AsmPrinter&, llvm::DenseMap<unsigned long, llvm::SmallVector<llvm::GlobalAlias const*, 1u>, llvm::DenseMapInfo<unsigned long, void>, llvm::detail::DenseMapPair<unsigned long, llvm::SmallVector<llvm::GlobalAlias const*, 1u>>>*) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:3147:19
#12 0x00000000031b6993 emitGlobalConstantImpl(llvm::DataLayout const&, llvm::Constant const*, llvm::AsmPrinter&, llvm::Constant const*, unsigned long, llvm::DenseMap<unsigned long, llvm::SmallVector<llvm::GlobalAlias const*, 1u>, llvm::DenseMapInfo<unsigned long, void>, llvm::detail::DenseMapPair<unsigned long, llvm::SmallVector<llvm::GlobalAlias const*, 1u>>>*) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:3458:5
#13 0x00000000031aaba8 llvm::AsmPrinter::emitGlobalConstant(llvm::DataLayout const&, llvm::Constant const*, llvm::DenseMap<unsigned long, llvm::SmallVector<llvm::GlobalAlias const*, 1u>, llvm::DenseMapInfo<unsigned long, void>, llvm::detail::DenseMapPair<unsigned long, llvm::SmallVector<llvm::GlobalAlias const*, 1u>>>*) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:3478:5
#14 0x00000000031aa539 llvm::AsmPrinter::emitGlobalVariable(llvm::GlobalVariable const*) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:861:3
#15 0x00000000031b1c80 llvm::AsmPrinter::doFinalization(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:2069:22
#16 0x0000000003c71d3e llvm::FPPassManager::doFinalization(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1494:16
#17 0x0000000003c6d93c (anonymous namespace)::MPPassManager::runOnModule(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1581:16
#18 0x0000000003c6d22d llvm::legacy::PassManagerImpl::run(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:535:16
#19 0x0000000003c71ef1 llvm::legacy::PassManager::run(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1672:3
#20 0x0000000000d1edec compileModule(char**, llvm::LLVMContext&) /home/henry/aflplusplus-isel/llvm-project/llvm/tools/llc/llc.cpp:737:41
#21 0x0000000000d1d192 main /home/henry/aflplusplus-isel/llvm-project/llvm/tools/llc/llc.cpp:418:13
#22 0x00007f37d7ec8c87 __libc_start_main /build/glibc-CVJwZb/glibc-2.27/csu/../csu/libc-start.c:344:0
#23 0x0000000000d1c99a _start (/home/henry/aflplusplus-isel/llvm-project/build-debug/bin/llc+0xd1c99a)

Cause

The following code from function emitGlobalConstantLargeInt in AsmPrinter.cpp tries to right shift Realigned by an amount ExtraBitSize in place. However, if the constant to emit has a bit width less than 64 and the bit width is not a multiple of 8, the shift amount will be greater than the bit width of Realigned, which causes the crash.

llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

Lines 3243 to 3274 in aecae68

	unsigned BitWidth = CI->getBitWidth();
	// Copy the value as we may massage the layout for constants whose bit width
	// is not a multiple of 64-bits.
	APInt Realigned(CI->getValue());
	uint64_t ExtraBits = 0;
	unsigned ExtraBitsSize = BitWidth & 63;
	if (ExtraBitsSize) {
	// The bit width of the data is not a multiple of 64-bits.
	// The extra bits are expected to be at the end of the chunk of the memory.
	// Little endian:
	// * Nothing to be done, just record the extra bits to emit.
	// Big endian:
	// * Record the extra bits to emit.
	// * Realign the raw data to emit the chunks of 64-bits.
	if (DL.isBigEndian()) {
	// Basically the structure of the raw data is a chunk of 64-bits cells:
	// 0 1 BitWidth / 64
	// [chunk1][chunk2] ... [chunkN].
	// The most significant chunk is chunkN and it should be emitted first.
	// However, due to the alignment issue chunkN contains useless bits.
	// Realign the chunks so that they contain only useful information:
	// ExtraBits 0 1 (BitWidth / 64) - 1
	// chu[nk1 chu][nk2 chu] ... [nkN-1 chunkN]
	ExtraBitsSize = alignTo(ExtraBitsSize, 8);
	ExtraBits = Realigned.getRawData()[0] &
	(((uint64_t)-1) >> (64 - ExtraBitsSize));
	Realigned.lshrInPlace(ExtraBitsSize);
	} else
	ExtraBits = Realigned.getRawData()[BitWidth / 64];
	}

[HazyFish]

cc @DataCorrupted

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

[HazyFish]

Candidate patch https://reviews.llvm.org/D138246

[HazyFish]

Fixed in fc1ffb4