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Introduction to Advanced Topics Chapter 1 Text Book: Advanced compiler Design implementation By Steven S Muchnick ( Elsevier ). Outline. Review of compiler structure Advanced issues in elementary topics The importance of optimizations Structure of optimizing compilers

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  1. Introduction to Advanced TopicsChapter 1Text Book: Advanced compiler Design implementationBySteven S Muchnick (Elsevier)

  2. Outline • Review of compiler structure • Advanced issues inelementary topics • The importance of optimizations • Structure of optimizing compilers • Placement of optimizations • Advanced topics

  3. Compiler Structure String of characters Scanner tokens Parser Symbol table and access routines OS Interface AST Semantic analyzer IR Code Generator Object code

  4. Advanced Issues inElementary Topics • Symbol table management(3) • Efficiency • Overloading • Type Inference • Intermediate Language Selection(4) • Run-Time Support(5) • Producing Code Generators (6)

  5. Intermediate Language Selection • Low Vs. High level control flow structures • Flat Vs. Hierarchical (tree) • Machine Vs. High level of instructions • (Symbolic) Registers Vs. Stack • Normal forms (SSA) • Intermediate forms: Control Flow Graph, Call Graph, Program Dependence Graph • Issues: Engineering, efficiency, portability, optimization level

  6. LIR s2 s1 s4  s3 s6  s5 L1: if s2 >s6 goto L2 s7  addr a s8  4*s9 s10  s7+s8 [s10]  2 s2  s2 + s4 goto L1 L2: MIR v v1 t2  v2 t3  v3 L1: if v >t3 goto L2 t4  addr a t5  4*i t6  t4+t5 *t6  2 v  v + t2 goto L1 L2: IRs in the Book HIR for v v1 by v2 to v3 do a[i] :=2 endfor

  7. Advanced Issues inElementary Topics • Symbol table management(3) • Efficiency • Overloading • Type Inference • Intermediate Language Selection(4) • Run-Time Support(5) • Producing Code Generators (6)

  8. Run-Time Support • Data representation and instructions • Register usage • Stack frames (activation records) • Parameter passing disciplines • Symbolic language support • Garbage Collection

  9. Advanced Issues inElementary Topics • Symbol table management(3) • Efficiency • Overloading • Type Inference • Intermediate Language Selection(4) • Run-Time Support(5) • Producing Code Generators (6)

  10. The Importance of Optimizations • One pass compilers produce slow code • Much of the time spent in loops • optimize loops • Machines can be simpler and faster if optimizing compilers are used (RISC, VLIW) • Programs are complex and general • Compilers need to be modular

  11. SPARC code ldw a, r1 ldw b, r2 add r1, r2, r3 stw r3, c ldw c, r3 add r3, 1, r4 stw r4, d Optimized SPARC code add r1, r2, r3 add r3, 1, r4 C code int a, b, c, d; c = a + b; d = c + 1; 2 cycles 10 cycles

  12. Application Dependent Optimizations • Functional programs • replacement of recursion by loops (tail-calls elimination) • replacement of heap by stack • Object Oriented Programs • Dead member elimination • Replacement of virtual by static function • Numeric Code • Database Code

  13. String String Scanner Scanner Tokens Tokens Parser Parser AST AST Semantic Semantic AST AST IR generator LIR generator MIR LIR Optimizer Optimizer MIR LIR Code generator Fin. assembly LIR Object Post. optimizer Object

  14. Mixed vs. Low Level Optimizers • Mixed • Sun-SPARC, Dec. Alpha, SGI-MIPS, Intel’s 386 • Easier to port • More efficient compilation? • Supports CISC • Low Level • HP-PA-RISC/IBM-Power PC • More efficient code • Conceptually simpler (in RISC) • Used for multiple programming languages

  15. Translation by Preprocessing • Some programming languages are translated into C • Elimination of includes, C++(cfront), Haskel • Quick and portable solution • C supports some indirect source level debugging • Other examples: Fortran into “vector” Fortran program

  16. Data-Cache Optimizations(20) String Scanner Tokens Parser AST Semantic HIR Data-cache optimizer MIR  Object

  17. String Scanner Tokens Parser AST Semantic AST LIR generator Low-to-High HIR=YIL LIR=XIL Data-cache optimizer Optimizer LIR HIR=YIL High-to-Low Fin. assembly Object IBM PowerPC compiler

  18. Outline • Review of compiler structure • Advanced issues inelementary topics • The importance of optimizations • Structure of optimizing compilers • Placement of optimizations • Advanced Topics

  19. Scalar replacement of array references Data-cache optimizations Procedure integration Tail-call elimination Scalar replacement of aggregates Sparse constant propagation Interprocedural constant propagation Procedure specialization and cloning Sparse conditional constant propagation Inline expansion Leaf-routine optimizations Instruction Scheduling 1 Register allocation Instruction Scheduling 2 Intraprocedural I-cache optimizations Instruction prefetching Data prefertching Branch predication Global value numbering Local and global copy propagation Sparse conditional constant propagation Dead code elimination Common Subexpression Elimination Loop invariant code motion Interprocedural register allocation Interprocedural I-cache optimization Partial redundency Elimination

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