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项目作者： filletofish

项目描述 ：
Sample of building control flow graph, SSA form, phi nodes, LLVM IR for imagined language.
高级语言： C++
项目地址: git://github.com/filletofish/compiler-touch.git
创建时间： 2017-05-31T19:18:32Z
项目社区：https://github.com/filletofish/compiler-touch
开源协议：
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Compiler-touch

Simple compiler frontend to generate intermediate representation for simple language.
The languange consists of integers, mutating variables, cycles and condition statements.

Two modes available:

  • Generating my own intermediate presentation with features:

    • Building Control Flow Graph
    • Using SSA Form
    • Using Phi Nodes

  • Generating LLVM intermediate presentation with power of LLVM Library.

Example:

Here is simple code written with our language.

Code:

  1. a = 3
  2. b = 0
  4. for i = 1, b in
  5.     a = a + 3
  7. if b then
  8.     a = a - 2
  9. else
  10.     a = 0

Control flow graph:



Its intermediate representation (using my own statements):

  1. bb #0 entry
  2.         preds: 
  3.         succs: bb #1 loop_cond 
  4.         dominatedBy: 
  5.     a_0 = 3
  6.     b_0 = 0
  7.     i_0 = 1
  8.     branch to: bb #1 loop_cond
  10. bb #1 loop_cond
  11.         preds: bb #0 entry bb #2 loop_body 
  12.         succs: bb #2 loop_body bb #3 loop_cont 
  13.         dominatedBy: bb #0 entry
  14.     i_1 = [i_0 bb #0 entry; i_2 bb #2 loop_body; ]
  15.     a_1 = [a_0 bb #0 entry; a_2 bb #2 loop_body; ]
  16.     branch on: b_0 - i_1 to: bb #2 loop_body or: bb #3 loop_cont
  18. bb #2 loop_body
  19.         preds: bb #1 loop_cond 
  20.         succs: bb #1 loop_cond 
  21.         dominatedBy: bb #1 loop_cond
  22.     a_2 = a_1 + 3
  23.     i_2 = i_1 + 1
  24.     branch to: bb #1 loop_cond
  26. bb #3 loop_cont
  27.         preds: bb #1 loop_cond 
  28.         succs: bb #5 else bb #4 then 
  29.         dominatedBy: bb #1 loop_cond
  30.     branch on: b_0 to: bb #5 else or: bb #4 then
  32. bb #4 then
  33.         preds: bb #3 loop_cont 
  34.         succs: bb #6 if_cont 
  35.         dominatedBy: bb #3 loop_cont
  36.     a_3 = a_1 - 2
  37.     branch to: bb #6 if_cont
  39. bb #5 else
  40.         preds: bb #3 loop_cont 
  41.         succs: bb #6 if_cont 
  42.         dominatedBy: bb #3 loop_cont
  43.     a_4 = 0
  44.     branch to: bb #6 if_cont
  46. bb #6 if_cont
  47.         preds: bb #4 then bb #5 else 
  48.         succs: 
  49.         dominatedBy: bb #3 loop_cont
  50.     a_5 = [a_3 bb #4 then; a_4 bb #5 else; ]

Its intermediate representation produced with LLVM Library:

  1. ; ModuleID = 'My Module'
  2. source_filename = "My Module"
  4. define common i32 @main() {
  5. entrypoint:
  6.   %a = alloca i32
  7.   store i32 3, i32* %a
  8.   %b = alloca i32
  9.   store i32 0, i32* %b
  10.   %i = alloca i32
  11.   store i32 1, i32* %i
  12.   br label %loopCoonditionBB
  14. loopCoonditionBB:                                 ; preds = %loop, %entrypoint
  15.   %b1 = load i32, i32* %b
  16.   %i2 = load i32, i32* %i
  17.   %loopcond = icmp slt i32 %i2, %b1
  18.   br i1 %loopcond, label %loop, label %afterloop
  20. loop:                                             ; preds = %loopCoonditionBB
  21.   %a3 = load i32, i32* %a
  22.   %addtmp = fadd i32 %a3, 3
  23.   store i32 %addtmp, i32* %a
  24.   %i4 = load i32, i32* %i
  25.   %nextvar = fadd i32 %i4, 1
  26.   store i32 %nextvar, i32* %i
  27.   br label %loopCoonditionBB
  29. afterloop:                                        ; preds = %loopCoonditionBB
  30.   %b5 = load i32, i32* %b
  31.   %ifcond = icmp ne i32 %b5, 0
  32.   br i1 %ifcond, label %then, label %else
  34. then:                                             ; preds = %afterloop
  35.   %a6 = load i32, i32* %a
  36.   %subtmp = fsub i32 %a6, 2
  37.   store i32 %subtmp, i32* %a
  38.   br label %ifcont
  40. else:                                             ; preds = %afterloop
  41.   store i32 0, i32* %a
  42.   br label %ifcont
  44. ifcont:                                           ; preds = %else, %then
  45.   %iftmp = phi i32 [ %subtmp, %then ], [ 0, %else ]
  46.   ret i32 %iftmp
  47. }

What is IR?

Wiki article

Ok, then. With LLVM installed you can look at IR of C language by yourself. Just write simple C program.

Use flag -emit-llvm and level of optimization -O0 (from 0 to 3):
clang -S -emit-llvm -O0 helloworld.c

Now hello.ll contains the IR.

Dependencies:

  • llvm 4.0
  • clang

Building:

  1. ./build.sh

Usage:

Printing intermediate representation:

  1. ./compiler <program.txt

Use cmd argument -gv for printing graph viz presentation

Use cmd argument -llvm for llvm mode

Sources: