How to create a ConstantInt in LLVM?

问题:

I'm not sure how to create a ConstantInt in LLVM- I know the number I would like to create, but I'm unsure how I can make a ConstantInt representing that number; I can't seem to find the constructor I need in the documentation.

I'm thinking it has to be along the lines of

ConstantInt consVal = new ConstantInt(something here). 

I know I want it to be an int type, and I know my value... I just want to create a number!

回答1:

Most things in LLVM are created through a static method call instead of directly using a constructor. One reason is that an existing object can be returned instead of creating a new instance.

The static members of ConstantInt have a number of creation methods. You're probably most interested in get (Type *Ty, uint64_t V, bool isSigned=false) and, if you don't already have an integer type, IntegerType::get (LLVMContext &C, unsigned NumBits).

回答2:

To make an a 32 bit integer:

llvm::ConstantInt::get(context, llvm::APInt(/*nbits*/32, value, /*bool*/is_signed)); 

回答3:

ConstantInt* const_int32  = ConstantInt::get( Context , APInt(32, StringRef("10"), 10)); 

where, APInt(32, StringRef("10"), 10); gets int value from string "10" with base 10.

回答4:

To create a 32-bit integer constant:

llvm::Type *i32_type = llvm::IntegerType::getInt32Ty(llvm_context); llvm::Constant *i32_val = llvm::ConstantInt::get(i32_type, -1/*value*/, true); 

文章来源: How to create a ConstantInt in LLVM?