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; ModuleID = 'while.c'
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source_filename = "while.c"
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-pc-linux-gnu"
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; 全局变量定义声明（已显式初始化值global前不用加common, 未显式初始化值统一赋值0）
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@a = common global i32 0, align 4
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@b = common global i32 0, align 4
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;Function 主函数入口
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define i32 @main() #0{
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0:
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; 同样预先分配一个%1并初始化为0
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%1 = alloca i32, align 4
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store i32 0, i32* %1, align 4
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; a 和 b不用再alloca，直接赋值
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store i32 0, i32* @b, align 4
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store i32 3, i32* @a, align 4
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; 一个基本块结束，进入while条件判断域
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br label %2
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2: ; preds = %0, %5 ; %0 为入口bb，%5为循环体bb
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;加载a值
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%3 = load i32, i32* @a, align 4
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; 比较 a>0
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%4 = icmp sgt i32 %3, 0
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; 根据while的cond表达式真假跳转， 为假标号得根据bb5中标号使用情况确定
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br i1 %4, label %5, label %11
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5: ;preds = %2
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;加载a值和b值
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%6 = load i32, i32* @b, align 4
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%7 = load i32, i32* @a, align 4
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; a+b
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%8 = add i32 %6, %7
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; 保存结果至b
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store i32 %8, i32* @b, align 4
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; a = a-1
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%9 = load i32, i32* @a, align 4
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%10 = sub i32 %9, 1
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store i32 %10, i32* @a, align 4
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; 循环体内部基本块结束，跳转至循环条件判断入口
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br label %2
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11: ;preds = %2
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;加载b值
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%12 = load i32, i32* @b, align 4
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ret i32 %12
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}
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attributes #0 = { noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
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!llvm.module.flags = !{!0}
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!llvm.ident = !{!1}
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!0 = !{i32 1, !"wchar_size", i32 4}
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!1 = !{!"clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)"} |
