Outline CS 412/413. Function calls. Stack layout. Tiling a call. Two translations

Transcription

1 CS 412/413 Introduction to Compilers nd Trnsltors Cornell University Andrew Myers Outline Implementing function clls Implementing functions Optimizing wy the pointer Dynmiclly-llocted structures strings nd rrys Register lloction the esy wy Lectur7 Finishing bsic genertion 3 Mrch 00 CS 412/413 Spring '00 Lectur7 -- Andrew Myers 2 Function clls How to generte for function clls? Two kinds of IR sttements in cnonicl form dest f EXP f bp old bp Stck lyout current stck bp old bp current stck new stck CS 412/413 Spring '00 Lectur7 -- Andrew Myers 3 CS 412/413 Spring '00 Lectur7 -- Andrew Myers 4 dest f non-risc push push dd, 4*n Two trnsltions RISC sub, 4*n mov [ + 4],... mov [ + 4*n], dd, 4*n CS 412/413 Spring '00 Lectur7 -- Andrew Myers 5 old? f Tiling cll push push dd, 4*n Problem doesn t fit into tiling prdigm; unbounded # tiles required Solution don t fold e i into tile Downside genertes lot of extr temporries f push t n push t 1 dd, 4*n CS 412/413 Spring '00 Lectur7 -- Andrew Myers 6 1

2 Compiling function bodies Function body S Z f () T = e [ = (RV, E Z e [) S Z f () = e [ = EXP(E Z e [) Vribles E Z v [ = TEMP(t v ) for E Z v [ = MEM(TEMP(FP) + k) for rgs Try it out f(x int, yint) = x + y CS 412/413 Spring '00 Lectur7 -- Andrew Myers 7 Abstrct ssembly for f f(x int, yint) = x + y RV + MEM MEM + + FP 8 FP 12 Wht s missing here? CS 412/413 Spring '00 Lectur7 -- Andrew Myers 8 Stck setup Need to set up stck on entry prev push bp mov bp, sub, 4*l mov, bp pop bp new new prev prev. prev. new new stck l Function f push bp mov bp, function prologue sub, 4*l f_epilogue mov, bp pop bp function epilogue CS 412/413 Spring '00 Lectur7 -- Andrew Myers 9 CS 412/413 Spring '00 Lectur7 -- Andrew Myers 10 Compiling urn Iot urn sttement urns immeditely from function. Trnsltion S Z urn e [ = SEQ((RV, E Z e [), JUMP(epilogue)) Every function f hs f prologue epilogue lbel f_epilogue body epilogue CS 412/413 Spring '00 Lectur7 -- Andrew Myers 11 The Glory of Pentium CISC f push ebp mov ebp,e sub e, 4*l f_epilogue mov e, ebp pop ebp enter 4*l, 0 f_epilogue leve CS 412/413 Spring '00 Lectur7 -- Andrew Myers 12 2

3 Optimizing wy ebp Ide mintin constnt offset k between pointer nd stck pointer Use RISC-style rgument pssing rther thn pushing rguments on stck All references to MEM(FP+n) trnslted to opernd [e+(n+k)] insted of to [ebp+n] Advntge get whole extr register to use when llocting registers (7!) CS 412/413 Spring '00 Lectur7 -- Andrew Myers 13 prev. prev Stck setup sub, 4*l dd, 4*l + 4*l prev prev new mx rg ce new stck (size 4*l) CS 412/413 Spring '00 Lectur7 -- Andrew Myers 14 Cvets Get even fster (nd RISC-core) prologue nd epilogue thn with enter/leve but Must sve ebp register if we wnt to use it (like e, cllee-sve) Doesn t work if stck is truly vrible-sized e.g., lloc() cll in C lloctes vrible-sized rry on the stck -- not problem in Iot where rrys hep-llocted Dynmic structures Modern progrmming lnguges llow dynmiclly llocted dt structures strings, rrys, objects C chr *x = (chr *)mlloc(strlen(s) + 1); C++ Foo *f = new Foo(); Jv Foo f = new Foo(); String s = s1 + s2; Iot x rry[int] = new int[5] (0); String s = s1 + s2; CS 412/413 Spring '00 Lectur7 -- Andrew Myers 15 CS 412/413 Spring '00 Lectur7 -- Andrew Myers 16 Progrm Hep Progrm hs 4 memory res segment, stck segment, sttic dt, hep Two typicl memory lyouts (OS-dep.) hep sttic dt stck stck hep sttic dt CS 412/413 Spring '00 Lectur7 -- Andrew Myers 17 Object lloction Dynmic objects llocted in the hep rry cretion, string conctention mlloc(n) urns new chunk of n bytes, free(x) releses memory strting t x Globls stticlly llocted in dt segment globl vribles string constnts ssembler supports dt segment declrtions stck hep sttic dt CS 412/413 Spring '00 Lectur7 -- Andrew Myers 18 3

4 rry[t] Iot dynmic structures.length elements of new T [n] ( e ) = mlloc(4*n + 4); MEM() = n; = + 4; 1 = ; 2 = + 4*n; while ( 1!= 2 ) ( MEM( 1 ) = E Ze[; 1 = ); PA4 We give you newrry, newstring clls with grbge collection support (no free cll needed) CS 412/413 Spring '00 Lectur7 -- Andrew Myers 19 Trivil register lloction Cn convert bstrct ssembly to rel ssembly esily (but generte bd ) Allocte every temporry to loction in the current stck rther thn to register Every temporry stored in different plce -- no possibility of conflict Three registers needed to shuttle dt in nd out of stck (mx. # registers used by one instruction) e.g, ex, ebx, ecx CS 412/413 Spring '00 Lectur7 -- Andrew Myers 20 Rewriting bstrct Given instruction, replce every temporry in instruction with one of three registers Add mov instructions before instruction to lod registers properly Add mov instructions fter instruction to put dt bck onto stck (if necessry) push t1 mov ex, [ - t1off]; push ex mov [+4], t3? dd t1, [ - 4]? Result Simple wy to get working Code is longer thn necessry, slower Also cn llocte temporries to registers until registers run out (3 temporries on Pentium, 20+ on MIPS, Alph) Code genertion technique ctully used by some compilers when ll optimiztion turned off (-O0) Will use for Progrmming Assignment 4 CS 412/413 Spring '00 Lectur7 -- Andrew Myers 21 CS 412/413 Spring '00 Lectur7 -- Andrew Myers 22 Summry Complete genertion technique Use tiling to perform instruction selection Arguments mpped to stck loctions, to temporries Function generted by gluing prologue, epilogue onto body Dynmic structure lloction hndled by relying on hep lloction routines (mlloc) Sttic structures llocted by dt segment ssembler declrtions Allocte temporries to stck loctions to eliminte use of unbounded # of registers Shuttle temporries in nd out using ex-ecx regs CS 412/413 Spring '00 Lectur7 -- Andrew Myers 23 Where we re High-level source Assembly CS 412/413 Spring '00 Lectur7 -- Andrew Myers 24 4

5 Further topics Generting better register lloction optimiztion (high- nd low-level) dtflow nlysis Supporting lnguge fetures objects, modules, polymorphism, first-clss functions, exceptions dvnced GC techniques dynmic linking, loding, & PIC dynmic types nd reflection Compiler-like progrms source-to-source trnsltion interpers CS 412/413 Spring '00 Lectur7 -- Andrew Myers 25 5