[llvm-dev] Landing Pad bug?

[Johan Wehrli via llvm-dev]

Hi Reid,

You can find the preprocess source here: https://reviews.llvm.org/P7928 <https://reviews.llvm.org/P7928>

This is the compile line used: llvm3.9/bin/clang++ -O2 integer.cpp -E &> preprocess.txt

Greetings,

Johan

> On 11 Oct 2016, at 18:02, Reid Kleckner <rnk at google.com> wrote:
> 
> That's an interesting bug. Can you post the pre-processed source code somewhere? I can't optimize the O0.ll file because it only contains the function, and none of the struct types.
> 
> Usually pre-processed source is large, so I wouldn't recommend mailing it to the list. I'd suggest our bugzilla, but you can't create new accounts right now without mailing llvm-admin.
> 
> On Mon, Oct 10, 2016 at 11:30 PM, Johan Wehrli via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>wrote:
> HI,
> 
> When compiling the open-source software cryptopp (https://www.cryptopp.com/#download <https://www.cryptopp.com/#download>) version 5.6.4 I found a strange issue with the IR generated.
> 
> The issue only appears when compiling with -O2 optimisation in the integer.cpp file (the function is _ZN8CryptoPPrsERNSt3__113basic_istreamIcNS0_11char_traitsIcEEEERNS_7IntegerE -> CryptoPP::operator>>(std::__1::basic_istream<char, std::__1::char_traits<char> >&, CryptoPP::Integer&)).
> 
> The verifier give me these errors:
> 
> EH pad cannot be in entry block. %4 = landingpad
> { i8*, i32 } cleanupLandingPadInst not the first non-PHI instruction in the block. %4 = landingpad { i8*, i32 } cleanup
> 
> If I remove the verifier, I am able to compile the whole library and run the test suite without any issue.
> 
> When you look at the whole IR code for the function:
> 
> ----------------------
> 
> ; Function Attrs: ssp uwtable
> define nonnull dereferenceable(168) %"class.std::__1::basic_istream"* @_ZN8CryptoPPrsERNSt3__113basic_istreamIcNS0_11char_traitsIcEEEERNS_7IntegerE(%"class.std::__1::basic_istream"* dereferenceable(168), %"class.CryptoPP::Integer"* dereferenceable(40)) local_unnamed_addr #0 personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
>   %3 = tail call i8* @_ZN8CryptoPP17UnalignedAllocateEm(i64 16)
>   %4 = landingpad { i8*, i32 }
>           cleanup
>   %5 = icmp eq i8* %3, null
>   br i1 %5, label %6, label %8, !prof !22
> 
> ; <label>:6:                                      ; preds = %2
>   invoke void @__assert_rtn(i8* getelementptr inbounds ([11 x i8], [11 x i8]* @__func__._ZN8CryptoPP20AllocatorWithCleanupIhLb0EE10deallocateEPvm, i64 0, i64 0), i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str.64, i64 0, i64 0), i32 197, i8* getelementptr inbounds ([32 x i8], [32 x i8]* @.str.75, i64 0, i64 0)) #58
>           to label %7 unwind label %10
> 
> ; <label>:7:                                      ; preds = %6
>   unreachable
> 
> ; <label>:8:                                      ; preds = %2
>   %9 = tail call { i64, i8* } asm sideeffect "rep stosb", "={cx},={di},{ax},0,1,~{memory},~{dirflag},~{fpsr},~{flags}"(i32 0, i64 16, i8* nonnull %3) #53, !srcloc !1070
>   invoke void @_ZN8CryptoPP19UnalignedDeallocateEPv(i8* nonnull %3)
>           to label %13 unwind label %10
> 
> ; <label>:10:                                     ; preds = %8, %6
>   %11 = landingpad { i8*, i32 }
>           catch i8* null
>   %12 = extractvalue { i8*, i32 } %11, 0
>   tail call void @__clang_call_terminate(i8* %12) #59
>   unreachable
> 
> ; <label>:13:                                     ; preds = %8
>   resume { i8*, i32 } %4
> }
> 
> ----------------------
> 
> I was not able to understand which optimisation transforms the code like this.
> 
> I have attached the IR code from the function in O0 and O2.
> 
> Greetings,
> 
> Johan
> 
> 
> 
> 
> 
> 
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