Initial code for parsing an LLVM IR file

From the Step 2 code here:

  llir/llvm#86 (comment)

main.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+    "log"
+
+    "github.com/kr/pretty"
+    "github.com/llir/llvm/asm"
+)
+
+func main() {
+    m, err := asm.ParseFile("target.ll")
+    if err != nil {
+        log.Fatalf("%+v", err)
+    }
+    pretty.Println(m)
+}

target.c

@@ -0,0 +1,9 @@
+int foo(int a, int b) {
+    int sum;
+    sum = a + b;
+    return sum;
+}
+
+int main() {
+    return foo(12, 30);
+}

target.ll

@@ -0,0 +1,69 @@
+; ModuleID = 'target.c'
+source_filename = "target.c"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux-gnu"
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local i32 @foo(i32, i32) #0 !dbg !7 {
+  %3 = alloca i32, align 4
+  %4 = alloca i32, align 4
+  %5 = alloca i32, align 4
+  store i32 %0, i32* %3, align 4
+  call void @llvm.dbg.declare(metadata i32* %3, metadata !11, metadata !DIExpression()), !dbg !12
+  store i32 %1, i32* %4, align 4
+  call void @llvm.dbg.declare(metadata i32* %4, metadata !13, metadata !DIExpression()), !dbg !14
+  call void @llvm.dbg.declare(metadata i32* %5, metadata !15, metadata !DIExpression()), !dbg !16
+  %6 = load i32, i32* %3, align 4, !dbg !17
+  %7 = load i32, i32* %4, align 4, !dbg !18
+  %8 = add nsw i32 %6, %7, !dbg !19
+  store i32 %8, i32* %5, align 4, !dbg !20
+  %9 = load i32, i32* %5, align 4, !dbg !21
+  ret i32 %9, !dbg !22
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local i32 @main() #0 !dbg !23 {
+  %1 = alloca i32, align 4
+  store i32 0, i32* %1, align 4
+  %2 = call i32 @foo(i32 12, i32 30), !dbg !26
+  ret i32 %2, !dbg !27
+}
+
+attributes #0 = { noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "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" }
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 8.0.1 (https://git.llvm.org/git/clang.git ccfe04576c13497b9c422ceef0b6efe99077a392) (https://git.llvm.org/git/llvm.git 295e7b4486abfc0f01e6d22276931165f324c61e)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "target.c", directory: "/home/jc/git_repos2/llir3")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 8.0.1 (https://git.llvm.org/git/clang.git ccfe04576c13497b9c422ceef0b6efe99077a392) (https://git.llvm.org/git/llvm.git 295e7b4486abfc0f01e6d22276931165f324c61e)"}
+!7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !10, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DILocalVariable(name: "a", arg: 1, scope: !7, file: !1, line: 1, type: !10)
+!12 = !DILocation(line: 1, column: 13, scope: !7)
+!13 = !DILocalVariable(name: "b", arg: 2, scope: !7, file: !1, line: 1, type: !10)
+!14 = !DILocation(line: 1, column: 20, scope: !7)
+!15 = !DILocalVariable(name: "sum", scope: !7, file: !1, line: 2, type: !10)
+!16 = !DILocation(line: 2, column: 9, scope: !7)
+!17 = !DILocation(line: 3, column: 11, scope: !7)
+!18 = !DILocation(line: 3, column: 15, scope: !7)
+!19 = !DILocation(line: 3, column: 13, scope: !7)
+!20 = !DILocation(line: 3, column: 9, scope: !7)
+!21 = !DILocation(line: 4, column: 12, scope: !7)
+!22 = !DILocation(line: 4, column: 5, scope: !7)
+!23 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 7, type: !24, scopeLine: 7, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!24 = !DISubroutineType(types: !25)
+!25 = !{!10}
+!26 = !DILocation(line: 8, column: 12, scope: !23)
+!27 = !DILocation(line: 8, column: 5, scope: !23)