SROA crash

[regehr]

define void @aliveMutateGeneratedTmpFunction.2() {
enter:
  %valptr = alloca i32, align 4
  store i32 0, ptr %valptr, align 4
  %barr = call ptr @llvm.launder.invariant.group.p0(ptr %valptr)
  ret void
}

; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(inaccessiblemem: readwrite)
declare ptr @llvm.launder.invariant.group.p0(ptr) #0

attributes #0 = { nocallback nofree nosync nounwind speculatable willreturn memory(inaccessiblemem: readwrite) }

regehr@john-home:~/out$ /home/regehr/llvm-project/for-alive/bin/opt -passes=sroa reduced.ll 
WARNING: You're attempting to print out a bitcode file.
This is inadvisable as it may cause display problems. If
you REALLY want to taste LLVM bitcode first-hand, you
can force output with the `-f' option.

opt: /home/regehr/llvm-project/llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp:668: void {anonymous}::PromoteMem2Reg::run(): Assertion `isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!"' 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/regehr/llvm-project/for-alive/bin/opt -passes=sroa reduced.ll
 #0 0x00007fe5253fe950 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMSupport.so.18git+0x1fe950)
 #1 0x00007fe5253fb95f llvm::sys::RunSignalHandlers() (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMSupport.so.18git+0x1fb95f)
 #2 0x00007fe5253fbab5 SignalHandler(int) Signals.cpp:0:0
 #3 0x00007fe524a42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007fe524a969fc __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #5 0x00007fe524a969fc __pthread_kill_internal ./nptl/pthread_kill.c:78:10
 #6 0x00007fe524a969fc pthread_kill ./nptl/pthread_kill.c:89:10
 #7 0x00007fe524a42476 gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #8 0x00007fe524a287f3 abort ./stdlib/abort.c:81:7
 #9 0x00007fe524a2871b _nl_load_domain ./intl/loadmsgcat.c:1177:9
#10 0x00007fe524a39e96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
#11 0x00007fe526625b3b (anonymous namespace)::PromoteMem2Reg::run() PromoteMemoryToRegister.cpp:0:0
#12 0x00007fe526625faf llvm::PromoteMemToReg(llvm::ArrayRef<llvm::AllocaInst*>, llvm::DominatorTree&, llvm::AssumptionCache*) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMTransformUtils.so.18git+0x225faf)
#13 0x00007fe526d3f7cd llvm::SROAPass::promoteAllocas(llvm::Function&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMScalarOpts.so.18git+0x33f7cd)
#14 0x00007fe526d5e275 llvm::SROAPass::runImpl(llvm::Function&, llvm::DomTreeUpdater&, llvm::AssumptionCache&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMScalarOpts.so.18git+0x35e275)
#15 0x00007fe526d5f310 llvm::SROAPass::runImpl(llvm::Function&, llvm::DominatorTree&, llvm::AssumptionCache&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMScalarOpts.so.18git+0x35f310)
#16 0x00007fe526d5f6d9 llvm::SROAPass::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMScalarOpts.so.18git+0x35f6d9)
#17 0x00007fe5286b7d86 llvm::detail::PassModel<llvm::Function, llvm::SROAPass, llvm::PreservedAnalyses, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMPasses.so.18git+0xb7d86)
#18 0x00007fe52cb83b01 llvm::detail::PassModel<llvm::Function, llvm::PassManager<llvm::Function, llvm::AnalysisManager<llvm::Function>>, llvm::PreservedAnalyses, llvm::AnalysisManager<llvm::Function>>::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMAMDGPUCodeGen.so.18git+0x383b01)
#19 0x00007fe525925877 llvm::ModuleToFunctionPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMCore.so.18git+0x325877)
#20 0x00007fe52cb63296 llvm::detail::PassModel<llvm::Module, llvm::ModuleToFunctionPassAdaptor, llvm::PreservedAnalyses, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMAMDGPUCodeGen.so.18git+0x363296)
#21 0x00007fe5259238f1 llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) (/home/regehr/llvm-project/for-alive/bin/../lib/libLLVMCore.so.18git+0x3238f1)
#22 0x0000555889e2f034 llvm::runPassPipeline(llvm::StringRef, llvm::Module&, llvm::TargetMachine*, llvm::TargetLibraryInfoImpl*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::ToolOutputFile*, llvm::StringRef, llvm::ArrayRef<llvm::PassPlugin>, llvm::opt_tool::OutputKind, llvm::opt_tool::VerifierKind, bool, bool, bool, bool, bool, bool, bool) (/home/regehr/llvm-project/for-alive/bin/opt+0x31034)
#23 0x0000555889e1d09c main (/home/regehr/llvm-project/for-alive/bin/opt+0x1f09c)
#24 0x00007fe524a29d90 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#25 0x00007fe524a29e40 call_init ./csu/../csu/libc-start.c:128:20
#26 0x00007fe524a29e40 __libc_start_main ./csu/../csu/libc-start.c:379:5
#27 0x0000555889e20f95 _start (/home/regehr/llvm-project/for-alive/bin/opt+0x22f95)
Aborted (core dumped)
regehr@john-home:~/out$ 

cc @Hatsunespica

[antoniofrighetto]

Dumping AS leads to:

Slices of alloca:   %valptr = alloca i32, align 4
  [0,4) slice #0 (splittable)
    used by:   store i32 0, ptr %valptr, align 4

It seems that AllocaSlices doesn't take into account the fact that the alloca is used by the intrinsic as well, nor we bail out when NewAI doesn't seem to refine the current AI here:

llvm-project/llvm/lib/Transforms/Scalar/SROA.cpp

Lines 4583 to 4588 in ed86e74

	if (SliceTy == AI.getAllocatedType() && P.beginOffset() == 0) {
	NewAI = &AI;
	// FIXME: We should be able to bail at this point with "nothing changed".
	// FIXME: We might want to defer PHI speculation until after here.
	// FIXME: return nullptr;
	} else {

Hence, we continue with rewriting the alloca partition, and we happen to push the alloca in PromotableAlloca here (despite checking that it is not isAllocaPromotable early in SROA::runImpl:

llvm-project/llvm/lib/Transforms/Scalar/SROA.cpp

Lines 4665 to 4667 in ed86e74

	if (PHIUsers.empty() && SelectUsers.empty()) {
	// Promote the alloca.
	PromotableAllocas.push_back(NewAI);