forked from OSchip/llvm-project
c1709d387e
Member pointers in the MS ABI are made complicated due to the following: - Virtual methods in the most derived class (MDC) might live in a vftable in a virtual base. - There are four different representations of member pointer: single inheritance, multiple inheritance, virtual inheritance and the "most general" representation. - Bases might have a *more* general representation than classes which derived from them, a most surprising result. We believed that we could treat all member pointers as-if they were a degenerate case of the multiple inheritance model. This fell apart once we realized that implementing standard member pointers using this ABI requires referencing members with a non-zero vbindex. On a bright note, all but the virtual inheritance model operate rather similarly. The virtual inheritance member pointer representation awkwardly requires a virtual base adjustment in order to refer to entities in the MDC. However, the first virtual base might be quite far from the start of the virtual base. This means that we must add a negative non-virtual displacement. However, things get even more complicated. The most general representation interprets vbindex zero differently from the virtual inheritance model: it doesn't reference the vbtable at all. It turns out that this complexity can increase for quite some time: consider a derived to base conversion from the most general model to the multiple inheritance model... To manage this complexity we introduce a concept of "normalized" member pointer which allows us to treat all three models as the most general model. Then we try to figure out how to map this generalized member pointer onto the destination member pointer model. I've done my best to furnish the code with comments explaining why each adjustment is performed. This fixes PR23878. llvm-svn: 240384 |
||
|---|---|---|
| .. | ||
| ARCMigrate | ||
| AST | ||
| ASTMatchers | ||
| Analysis | ||
| Basic | ||
| CodeGen | ||
| Driver | ||
| Edit | ||
| Format | ||
| Frontend | ||
| FrontendTool | ||
| Headers | ||
| Index | ||
| Lex | ||
| Parse | ||
| Rewrite | ||
| Sema | ||
| Serialization | ||
| StaticAnalyzer | ||
| Tooling | ||
| CMakeLists.txt | ||
| Makefile | ||