[PATCH] D137217: [LTO][COFF] Use bitcode file names in lto native object file names.

[Teresa Johnson via Phabricator via cfe-commits]

tejohnson added a comment.

@MaskRay wondering if this is a good change to make for ELF as well, wdyt?



================
Comment at: clang/lib/CodeGen/BackendUtil.cpp:1104
 
-  auto AddStream = [&](size_t Task) {
+  auto AddStream = [&](size_t Task, Twine File) {
     return std::make_unique<CachedFileStream>(std::move(OS),
----------------
zequanwu wrote:
> tejohnson wrote:
> > I think you might need to mark the new parameter as unused here and in other cases where it isn't used via LLVM_ATTRIBUTE_UNUSED, to avoid build warnings - I can't recall how strictly that is enforced.
> LLVM_ATTRIBUTE_UNUSED is used to suppress unused functions. For unused parameter, I don't see any build warnings when compiling with this patch. I feel like it's very common to have unused parameter. 
LLVM_ATTRIBUTE_UNUSED maps to __attribute__((__unused__)) which works for either functions or parameters. However, I see where the macro is defined in llvm/include/llvm/Support/Compiler.h that using "(void)unused;" is preferred. Either one works (see below). However, it must be the case that there are no bots building with -Wunused-parameter, since I see Task is also unused here. So nevermind this suggestion, since what you have currently is consistent with what is already done here.

```
$ cat unused.cc
int foo(int x1, int x2 __attribute__((__unused__)), int x3) {
  (void)x3;
  return 1;
}
$ clang++ -c unused.cc -Wunused-parameter
unused.cc:1:13: warning: unused parameter 'x1' [-Wunused-parameter]
int foo(int x1, int x2 __attribute__((__unused__)), int x3) {
            ^
1 warning generated.
```


================
Comment at: lld/COFF/LTO.cpp:229
+    StringRef ltoObjName;
+    if (bitcodeFilePath == "ld-temp.o") {
+      ltoObjName =
----------------
zequanwu wrote:
> tejohnson wrote:
> > This case should always be i==0 I think?
> IIUC, "ld-temp.o" is the name of combined module. Do you mean there will be only 1 combined module and it will always be the first task?
Yes. So you don't need the handling for i==0 in the name in this case (you could probably assert that i==0).


================
Comment at: llvm/include/llvm/Support/Caching.h:53
 ///
 /// if (AddStreamFn AddStream = Cache(Task, Key))
 ///   ProduceContent(AddStream);
----------------
tejohnson wrote:
> This and possibly other header file descriptions need updates.
Can you add a note that ModuleName is the unique module identifier for the bitcode module the cache is being checked for.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D137217/new/

https://reviews.llvm.org/D137217