61 pages

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2004-09-22-LCPC LLVM Tutorial

Eddo - Chris Lattner

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61 pages

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The LLVM Compiler Framework and InfrastructureChris Lattner Vikram Advelattner@cs.uiuc.edu vadve@cs.uiuc.eduhttp://llvm.cs.uiuc.edu/LCPC Tutorial: September 22, 2004AcknowledgementsUIUC Contributors: External Contributors:v Tanya Brethour v Henrik Bachv Misha Brukman v Nate Begemanv Cameron Buschardt v Jeff Cohenv John Criswell v Paolo Invernizziv Alkis Evlogimenos v Brad Jonesv Brian Gaeke v Vladimir Merzliakovv Ruchira Sasanka vPrusv Anand Shukla v Reid Spencerv Bill WendlingFunding: This work is sponsored by the NSF Next Generation Software program through grants EIA-0093426 (an NSF CAREER award) and EIA-0103756. It is also supported in part by the NSF Operating Systems and Compilers program (grant #CCR-9988482), the NSF Embedded Systems program (grant #CCR-0209202), the MARCO/DARPA Gigascale Systems Research Center (GSRC), IBM through the DARPA-funded PERCS project, and the Motorola University Partnerships in Research program.http://llvm.cs.uiuc.edu/ Chris Lattner – lattner@cs.uiuc.eduLLVM Compiler Systemn The LLVM Compiler InfrastructurevProvides reusable components for building compilersvReduce the time/cost to build a new compilervBuild static compilers, JITs, trace-based optimizers, ...n The LLVM Compiler FrameworkvEnd-to-end compilers using the LLVM infrastructurevC and C++ are robust and aggressive:n Java, Scheme and others are in developmentvEmit C code or native code for X86, Sparc, PowerPChttp://llvm.cs.uiuc.edu/ Chris ...

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Publié par	Eddo
Nombre de lectures	77
Langue	English

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The LLVM Compiler Framework and Infrastructure

Chris Lattner lattner@cs.uiuc.edu

Vikram Adve vadve@cs.uiuc.edu

http://llvm.cs.uiuc.edu/

LCPC Tutorial: September 22, 2004

Acknowledgements

External Contributors: vHenrik Bach vNate Begeman vJeff Cohen vPaolo Invernizzi vBrad Jones vVladimir Merzliakov vVladimir Prus vReid Spencer

UIUC Contributors: vTanya Brethour vMisha Brukman vCameron Buschardt vJohn Criswell vAlkis Evlogimenos vBrian Gaeke vRuchira Sasanka vAnand Shukla vBill Wendling Funding: This work is sponsored by the NSF Next Generation Software program through grants EIA-0093426 (an NSF CAREER award) and EIA-0103756. It is also supported in part by the NSF Operating Systems and Compilers program (grant #CCR-9988482), the NSF Embedded Systems program (grant #CCR-0209202), the MARCO/DARPA Gigascale Systems Research Center (GSRC), IBM through the DARPA-funded PERCS project, and the Motorola University Partnerships in Research program.

http://llvm.cs.uiuc.edu/

Chris Lattner lattner@cs.uiuc.edu

LLVM Compiler System

nThe LLVM Compiler Infrastructure vProvides reusable components for building compilers vReduce the time/cost to build a new compiler vBuild static compilers, JITs, trace-based optimizers, ...

nThe LLVM Compiler Framework vEnd-to-end compilers using the LLVM infrastructure vC and C++ are robust and aggressive: nJava, Scheme and others are in development vEmit C code or native code for X86, Sparc, PowerPC

http://llvm.cs.uiuc.edu/

Chris Lattner lattner@cs.uiuc.edu

Three primary LLVM components

nThe LLVMVirtual Instruction Set vThe common language- and target-independent IR vInternal (IR) and external (persistent) representation

nA collection of well-integrated libraries vAnalyses, optimizations, code generators, JIT compiler, garbage collection support, profiling,

nA collection of tools built from the libraries vAssemblers, automatic debugger, linker, code generator, compiler driver, modular optimizer,

http://llvm.cs.uiuc.edu/

Chris Lattner lattner@cs.uiuc.edu

Tutorial Overview

nIntroduction to the running example nLLVM C/C++ Compiler Overview vHigh-level view of an example LLVM compiler nThe LLVM Virtual Instruction Set vIR overview and type-system nLLVM C++ IR and important API’s vBasics, PassManager, dataflow, ArgPromotion nImportant LLVM Tools vopt, code generator, JIT, test suite, bugpoint nExample applications of LLVM

http://llvm.cs.uiuc.edu/

Chris Lattner lattner@cs.uiuc.edu

Running example: arg promotion

Consider use of by-reference parameters: int callee(const int &X) { int callee(const int *X) { return X+1; return *X+1;// memory load } } int caller() {compiles toint caller() { return callee(4); int tmp;// stack object } tmp = 4;// memory store return callee(&tmp);

We want: int callee(int X) { return X+1; } int caller() { return callee(4); }

http://llvm.cs.uiuc.edu/

}

üEliminated load in callee üEliminated store in caller üEliminated stack slot for ‘tmp’

Chris Lattner lattner@cs.uiuc.edu

Why is this hard?

nRequires interprocedural analysis: vMust change the prototype of the callee vMust update all call sitesàwe mustknowall callers vWhat about callers outside the translation unit? nRequires alias analysis: vReference could alias other pointers in callee vMust know that loaded value doesn’t change from function entry to the load vMust know the pointer is not being stored through nReference might not be to a stack object!

http://llvm.cs.uiuc.edu/

Chris Lattner lattner@cs.uiuc.edu

Tutorial Overview

http://llvm.cs.uiuc.edu/

Chris Lattner lattner@cs.uiuc.edu

The LLVM C/C++ Compiler

nthe high level, it is a standard compiler:From vCompatible with standard makefiles vUses GCC 3.4 C and C++ parser

C file llvmgcc .o file llvm linker executable C++ file llvmg++ .o file

Compile Time Link Time nDistinguishing features: vUses LLVM optimizers, not GCC optimizers v.o files contain LLVM IR/bytecode, not machine code vExecutable can be bytecode (JIT’d) or machine code

http://llvm.cs.uiuc.edu/

Chris Lattner lattner@cs.uiuc.edu

Looking into events at compile-time

C file llvmgcc .o file

C to LLVM Compile-time Frontend Optimizer “cc1 “gccas

C++ file llvmg++ .o file

C++ to LLVM Compile-time Frontend Optimizer “cc1plus “gccas

M LLVM IR io LLVM 40 LLVM Analysis & d LLVM .bc ++ E Parser R Verifier Optimization Passes L File Writer t file Lowers o owers ++ o LVM

Dead Global Elimination, IP Constant Propagation, Dead Argument Elimination, Inlining, Reassociation, LICM, Loop Opts, Memory Promotion, Dead Store Elimination, ADCE,

http://llvm.cs.uiuc.edu/

Chris Lattner lattner@cs.uiuc.edu

Looking into events at link-time

.o file LLVM .o file Linker

.o file llvm linker executable .o file

Link-time Optimizer

20 LLVM Analysis & Optimization Passes Optionally “internalizes: marks most functions as internal, to improve IPO

Perfect place for argument promotion optimization!

http://llvm.cs.uiuc.edu/

.bc file for LLVM JIT NaBtiavcek Code Native executable end “llc BCa cCkoedned C Compiler “llc march=c “gcc

Link in native .o files and libraries here

Native executable

Chris Lattner lattner@cs.uiuc.edu

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