llvm dev - Oct 2020 - Creating a global variable for a struct array

>The type you pass to GlobalVariable's constructor for that variable
should be "[10 x %struct.dlist]" because that's what you want
storage
for. Then the GlobalVariable itself will be a Constant of type "[10 x
%struct.dlist]*".

Yes, I verified that this is the case.

I enabled assertions and the error seems to occur while creating GlobalVariable
for both struct dhash and struct dlist.




Here is a simpler version of the code causing error:

//struct dhash
typedef struct dhash{
char* filenm;
int n;
}dhash;

//create global variable to hold filename string
Constant *filenmInit = ConstantDataArray::getString(M.getContext(),
"myfile.txt");
Constant *filenmConst = new GlobalVariable(M, filenmInit->getType(), false,
                                     GlobalVariable::ExternalLinkage,
filenmInit, ".filenm");

//create global variable for int
Constant* intInit = ConstantInt::get(Type::getInt32Ty(M.getContext()), 10);
Constant* intConst = new GlobalVariable(M, intInit->getType(), false,
                                           GlobalVariable::ExternalLinkage,
intInit, ".int");

//create ConstantStruct for each hashtable entry
Constant *dhashInit[] = {filenmConst, intConst};
Constant *dhashConst = ConstantStruct::get(dhashTy, dhashInit);

Constant* htabInitArr[2];
htabInitArr[0] = dhashConst;
htabInitArr[1] = dhashConst;

    ArrayType *htabTy = ArrayType::get(dhashTy, 2);
    Constant *htabInit = ConstantArray::get(htabTy,
makeArrayRef(htabInitArr,2));
    GlobalVariable *htabConst = new GlobalVariable(M, htabInit->getType(),
false,
                                            GlobalVariable::ExternalLinkage,
htabInit, "htab");





Here is the error message:

opt: /home/chaitra/llvm-5-src/lib/IR/Constants.cpp:879:
llvm::ConstantAggregate::ConstantAggregate(llvm::CompositeType*,
llvm::Value::ValueTy, llvm::ArrayRef<llvm::Constant*>): Assertion
`V[I]->getType() == T->getTypeAtIndex(I) && "Initializer for
composite element doesn't match!"' failed.
#0 0x0000000001e558fa (opt+0x1e558fa)
#1 0x0000000001e5366e (opt+0x1e5366e)
#2 0x0000000001e537e2 (opt+0x1e537e2)
#3 0x00007f8a98a55390 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x11390)
#4 0x00007f8a977c7438 gsignal
/build/glibc-e6zv40/glibc-2.23/signal/../sysdeps/unix/sysv/linux/raise.c:54:0
#5 0x00007f8a977c903a abort /build/glibc-e6zv40/glibc-2.23/stdlib/abort.c:91:0
#6 0x00007f8a977bfbe7 __assert_fail_base
/build/glibc-e6zv40/glibc-2.23/assert/assert.c:92:0
#7 0x00007f8a977bfc92 (/lib/x86_64-linux-gnu/libc.so.6+0x2dc92)
#8 0x000000000189c982 (opt+0x189c982)
#9 0x000000000189cc7c (opt+0x189cc7c)
#10 0x00000000018a93e0 (opt+0x18a93e0)
#11 0x00000000018a95f3 (opt+0x18a95f3)
#12 0x00007f8a9758e59a iospecns::storage_bitcode::runOnModule(llvm::Module&)
(/home/chaitra/Desktop/iospec_test/test/build/proj/libstorage_bitcode.so+0x459a)
#13 0x00000000019473ad (opt+0x19473ad)
#14 0x00000000006db61c (opt+0x6db61c)
#15 0x00007f8a977b2840 __libc_start_main
/build/glibc-e6zv40/glibc-2.23/csu/../csu/libc-start.c:325:0
#16 0x0000000000747519 (opt+0x747519)
Stack dump:
0. Program arguments: opt -load
/home/chaitra/Desktop/iospec_test/test/build/proj/libstorage_bitcode.so
-storage_bitcode
1. Running pass 'storage_bitcode' on module '<stdin>'.
Aborted (core dumped)


Thanks,
Chaitra

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On Thu, 1 Oct 2020 at 16:01, Niddodi, Chaitra <chaitra at illinois.edu>
wrote:
> //create global variable to hold filename string
> Constant *filenmInit = ConstantDataArray::getString(M.getContext(),
"myfile.txt");
> Constant *filenmConst = new GlobalVariable(M, filenmInit->getType(),
false,
>                                      GlobalVariable::ExternalLinkage,
filenmInit, ".filenm");
filenmConst's LLVM type is "[12 x i8]*" (or similar if I've
miscounted), but I assume the slot in the struct is i8*. So you need
either a bitcast or a getelementptr constant expression to convert it.

Cheers.

Tim.

The error still persists despite adding the following cast:


filenmConst = ConstantExpr::getBitCast(filenmConst,
Type::getInt8PtrTy(M.getContext()));



That's why I had omitted this line from code earlier.

Thanks,
Chaitra
________________________________
From: Tim Northover <t.p.northover at gmail.com>
Sent: Thursday, October 1, 2020 12:53
To: Niddodi, Chaitra
Cc: llvm-dev at lists.llvm.org
Subject: Re: [llvm-dev] Creating a global variable for a struct array

On Thu, 1 Oct 2020 at 16:01, Niddodi, Chaitra <chaitra at illinois.edu>
wrote:
> //create global variable to hold filename string
> Constant *filenmInit = ConstantDataArray::getString(M.getContext(),
"myfile.txt");
> Constant *filenmConst = new GlobalVariable(M, filenmInit->getType(),
false,
>                                      GlobalVariable::ExternalLinkage,
filenmInit, ".filenm");
filenmConst's LLVM type is "[12 x i8]*" (or similar if I've
miscounted), but I assume the slot in the struct is i8*. So you need
either a bitcast or a getelementptr constant expression to convert it.

Cheers.

Tim.
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>filenmConst's LLVM type is "[12 x i8]*" (or similar if
I've
miscounted), but I assume the slot in the struct is i8*. So you need
either a bitcast or a getelementptr constant expression to convert it.

The error still persists despite adding the following cast:
filenmConst = ConstantExpr::getBitCast(filenmConst,
Type::getInt8PtrTy(M.getContext()));
That's why I had omitted this line from code earlier.





Also, the same type mismatch error occurs when I try to create a GlobalVariable
for a struct with 2 int fields as follows:

//struct dhash
typedef struct dhash{
int m;
int n;
}dhash;

//create global variable for int
Constant* intInit1 = ConstantInt::get(Type::getInt32Ty(M.getContext()), 11);
      Constant* intConst1 = new GlobalVariable(M, intInit1->getType(), false,
                                                   
GlobalVariable::ExternalLinkage, intInit1, ".int1");

//create global variable for int
      Constant* intInit = ConstantInt::get(Type::getInt32Ty(M.getContext()),
10);
      Constant* intConst = new GlobalVariable(M, intInit->getType(), false,
                                                   
GlobalVariable::ExternalLinkage, intInit, ".int");

      //create ConstantStruct for each hashtable entry
      Constant *dhashInit[] = {intConst1, intConst};//{filenmConst, intConst};
      Constant *dhashConst = ConstantStruct::get(dhashTy, dhashInit);

      Constant* htabInitArr[2];
      htabInitArr[0] = dhashConst;
      htabInitArr[1] = dhashConst;

    ArrayType *htabTy = ArrayType::get(dhashTy, 2);
    Constant *htabInit = ConstantArray::get(htabTy,
makeArrayRef(htabInitArr,2));
    GlobalVariable *htabConst = new GlobalVariable(M, htabInit->getType(),
false,
                                            GlobalVariable::ExternalLinkage,
htabInit, "htab");




struct dhash in LLVM IR is as follows:

%struct.dhash = type { i32, i32 }


So, I'm not sure why the error occurs ?

Thanks,
Chaitra
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