[WASM] v1i8 / v1i16 crashes backend with invalid Bitcast when targeting bleeding-edge

[HazyFish]

Description

When targeting WASM bleeding-edge, the following code crashes backend with assertion VT.getSizeInBits() == Operand.getValueSizeInBits() && "Cannot BITCAST between types of different sizes!" failed during WebAssembly Instruction Selection.

The code can successfully compile when targeting WASM without specifying -mcpu=bleeding-edge.

The problem exists for v1i8 / v1i16, but it does not exist for v1i32 / v1i64.

Minimal Reproduction

https://godbolt.org/z/T44czsqWr

Code

define <1 x i16> @f(<1 x i16> %0) {
BB:
  %B2 = srem <1 x i16> %0, %0
  br label %BB1

BB1:                                             ; preds = %BB
  %B = urem <1 x i16> %B2, <i16 3>
  ret <1 x i16> %B
}

Stack Trace

llc: /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:5530: llvm::SDValue llvm::SelectionDAG::getNode(unsigned int, const llvm::SDLoc &, llvm::EVT, llvm::SDValue, const llvm::SDNodeFlags): Assertion `VT.getSizeInBits() == Operand.getValueSizeInBits() && "Cannot BITCAST between types of different sizes!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: ./llvm-project-latest/build-debug/bin/llc -mtriple=wasm64 -mcpu=bleeding-edge ./crash-reports/dagisel-wasm64/bleeding-edge/1.ll
1.	Running pass 'Function Pass Manager' on module './crash-reports/dagisel-wasm64/bleeding-edge/1.ll'.
2.	Running pass 'WebAssembly Instruction Selection' on function '@f'
 #0 0x00007f9e979c0f2a llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/Support/Unix/Signals.inc:567:11
 #1 0x00007f9e979c10db PrintStackTraceSignalHandler(void*) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/Support/Unix/Signals.inc:641:1
 #2 0x00007f9e979bf756 llvm::sys::RunSignalHandlers() /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/Support/Signals.cpp:104:5
 #3 0x00007f9e979c1805 SignalHandler(int) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/Support/Unix/Signals.inc:412:1
 #4 0x00007f9e96155980 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12980)
 #5 0x00007f9e95451e87 raise /build/glibc-CVJwZb/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 #6 0x00007f9e954537f1 abort /build/glibc-CVJwZb/glibc-2.27/stdlib/abort.c:81:0
 #7 0x00007f9e954433fa __assert_fail_base /build/glibc-CVJwZb/glibc-2.27/assert/assert.c:89:0
 #8 0x00007f9e95443472 (/lib/x86_64-linux-gnu/libc.so.6+0x30472)
 #9 0x00007f9e981528d0 llvm::SelectionDAG::getNode(unsigned int, llvm::SDLoc const&, llvm::EVT, llvm::SDValue, llvm::SDNodeFlags) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:0:5
#10 0x00007f9e981371fd llvm::SelectionDAG::getNode(unsigned int, llvm::SDLoc const&, llvm::EVT, llvm::SDValue) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:5149:10
#11 0x00007f9e9813e28a llvm::SelectionDAG::getBitcast(llvm::EVT, llvm::SDValue) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:2229:10
#12 0x00007f9e97e40ab6 (anonymous namespace)::DAGCombiner::visitEXTRACT_SUBVECTOR(llvm::SDNode*) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:22304:22
#13 0x00007f9e97df1045 (anonymous namespace)::DAGCombiner::visit(llvm::SDNode*) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1792:40
#14 0x00007f9e97df0108 (anonymous namespace)::DAGCombiner::combine(llvm::SDNode*) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1828:10
#15 0x00007f9e97def716 (anonymous namespace)::DAGCombiner::Run(llvm::CombineLevel) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1626:18
#16 0x00007f9e97deefff llvm::SelectionDAG::Combine(llvm::CombineLevel, llvm::AAResults*, llvm::CodeGenOpt::Level) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:25586:3
#17 0x00007f9e981c000f llvm::SelectionDAGISel::CodeGenAndEmitDAG() /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:785:3
#18 0x00007f9e981bfbbd llvm::SelectionDAGISel::SelectBasicBlock(llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction, true, false, void>, false, true>, llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction, true, false, void>, false, true>, bool&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:701:1
#19 0x00007f9e981bf64d llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:1641:11
#20 0x00007f9e981bcb27 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:480:3
#21 0x00007f9ea4be15aa (anonymous namespace)::WebAssemblyDAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp:61:5
#22 0x00007f9e9b1d51d5 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/CodeGen/MachineFunctionPass.cpp:91:8
#23 0x00007f9e9a31d676 llvm::FPPassManager::runOnFunction(llvm::Function&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/IR/LegacyPassManager.cpp:1430:23
#24 0x00007f9e9a3224a2 llvm::FPPassManager::runOnModule(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/IR/LegacyPassManager.cpp:1476:16
#25 0x00007f9e9a31df49 (anonymous namespace)::MPPassManager::runOnModule(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/IR/LegacyPassManager.cpp:1545:23
#26 0x00007f9e9a31dabd llvm::legacy::PassManagerImpl::run(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/IR/LegacyPassManager.cpp:535:16
#27 0x00007f9e9a322781 llvm::legacy::PassManager::run(llvm::Module&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/lib/IR/LegacyPassManager.cpp:1672:3
#28 0x0000000000419b16 compileModule(char**, llvm::LLVMContext&) /home/henry/aflplusplus-isel/llvm-project-latest/llvm/tools/llc/llc.cpp:737:41
#29 0x0000000000417eaa main /home/henry/aflplusplus-isel/llvm-project-latest/llvm/tools/llc/llc.cpp:418:13
#30 0x00007f9e95434c87 __libc_start_main /build/glibc-CVJwZb/glibc-2.27/csu/../csu/libc-start.c:344:0
#31 0x00000000004176aa _start (./llvm-project-latest/build-debug/bin/llc+0x4176aa)

Cause

In the following code from method DAGCombiner::visitEXTRACT_SUBVECTOR:

In Line 22301, Src is t3: i32 = Constant<0>.
In Line 22303, Src becomes t4: v8i16 = BUILD_VECTOR Constant:i32<0>, Constant:i32<0>, Constant:i32<0>, Constant:i32<0>, Constant:i32<0>, Constant:i32<0>, Constant:i32<0>, Constant:i32<0>.
In Line 22304, DAG.getBitcast is called with 2 types of different size (v1i16 and v8i16), causing the assertion error.

llvm-project/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

Lines 22300 to 22305 in 8ab032f

	if (NumElems == 1) {
	SDValue Src = V->getOperand(IdxVal);
	if (EltVT != Src.getValueType())
	Src = DAG.getNode(ISD::TRUNCATE, SDLoc(N), InVT, Src);
	return DAG.getBitcast(NVT, Src);
	}

When not specifying bleeding-edge, the DAGCombiner::visitEXTRACT_SUBVECTOR method is not called.

[HazyFish]

cc @DataCorrupted

[llvmbot]

@llvm/issue-subscribers-backend-webassembly

[dschuff]

Just enabling SIMD by itself (i.e. specifying -mattr=+simd128) is also enough to reproduce. It also reproduces for wasm32

[junparser]

try to fix this in https://reviews.llvm.org/D145757

[junparser]

done