Book Image

Getting Started with LLVM Core Libraries

Book Image

Getting Started with LLVM Core Libraries

Overview of this book

Table of Contents (17 chapters)
Getting Started with LLVM Core Libraries
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Introducing the LLVM IR language syntax


Observe the LLVM IR assembly file, sum.ll:

target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.7.0"

define i32 @sum(i32 %a, i32 %b) #0 {
entry:
  %a.addr = alloca i32, align 4
  %b.addr = alloca i32, align 4
  store i32 %a, i32* %a.addr, align 4
  store i32 %b, i32* %b.addr, align 4
  %0 = load i32* %a.addr, align 4
  %1 = load i32* %b.addr, align 4
  %add = add nsw i32 %0, %1
  ret i32 %add
}

attributes #0 = { nounwind ssp uwtable ... }

The contents of an entire LLVM file, either assembly or bitcode, are said to define an LLVM module. The module is the LLVM IR top-level data structure. Each module contains a sequence of functions, which contains a sequence of basic blocks that contain a sequence of instructions. The module also contains peripheral entities to support this model, such as global variables...