Question

我使用 Clang作为库来编译一些模板化代码：

awk

不幸的是，编译的LLVM IR实际上并不包含template<typename T> T getSevenTemplated() { return 7; } int getSeven() { return getSevenTemplated<int>(); }的实现：

getSevenTemplated<int>

以下是我用于生成LLVM模块的代码：

; ModuleID = './test.cpp'
source_filename = "./test.cpp"
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.12.0"

; Function Attrs: ssp uwtable
define i32 @_Z8getSevenv() #0 {
entry:
  %call = call i32 @_Z17getSevenTemplatedIiET_v()
  ret i32 %call
}

declare i32 @_Z17getSevenTemplatedIiET_v() #1

attributes #0 = { ssp 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"="penryn" "target-features"="+cx16,+fxsr,+mmx,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { "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-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+fxsr,+mmx,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }

!llvm.module.flags = !{!0}
!llvm.ident = !{!1}

!0 = !{i32 1, !"PIC Level", i32 2}
!1 = !{!"clang version 5.0.0 (trunk 292778)"}

为了调查原因，我浏览了the source-code，发现auto* context = new llvm::LLVMContext(); // TODO: Fix leak auto codeGenerator = std::shared_ptr<clang::CodeGenerator>( clang::CreateLLVMCodeGen( compilerInstance.getDiagnostics(), filePath, compilerInstance.getHeaderSearchOpts(), preprocessor.getPreprocessorOpts(), compilerInstance.getCodeGenOpts(), *context, nullptr)); codeGenerator->Initialize(compilerInstance.getASTContext()); // declGroups are found by calling ParseAST with a special ASTConsumer earlier for (auto declGroup : declGroups) { codeGenerator->HandleTopLevelDecl(declGroup); } codeGenerator->HandleTranslationUnit(compilerInstance.getASTContext());具有处理模板的特定逻辑：它似乎跳过了函数模板实例化！我认为它处理生成的函数，但我不知道它是如何工作的。

我的问题是：

在较高的层面上，Clang如何实例化模板并将它们传递给CodeGenerator以生成代码？
是否有任何特殊技巧可以为实例化模板生成函数体？我在上面的代码中遗漏了什么？

Answer 1

问题是我打开了增量解析。启用此设置后，ParseAST函数不会调用clang::Sema::ActOnEndOfTranslationUnit，这会触发模板的实例化。

诀窍是在处理你的decl之后添加这个调用：

// This triggers the instantiation of templated functions
sema.ActOnEndOfTranslationUnit();

如何通过Clang编译模板实例化？

1 个答案: