[PATCH] D142484: [LinkerWrapper] Only import static libraries with needed symbols

Tue Jan 24 14:23:12 PST 2023

jhuber6 marked an inline comment as done.
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In D142484#4078377 <https://reviews.llvm.org/D142484#4078377>, @tra wrote:

> LGTM. Please wait a bit before landing it, in case @MaskRay has something to say.

I'm somewhat hoping to get this in before the fork that happens in a few hours.

================
Comment at: clang/test/Driver/linker-wrapper-libs.c:38-39
+
+// LIBRARY-RESOLVES: clang{{.*}} -o {{.*}}.img --target=amdgcn-amd-amdhsa -mcpu=gfx1030 {{.*}}.o {{.*}}.o
+// LIBRARY-RESOLVES: clang{{.*}} -o {{.*}}.img --target=nvptx64-nvidia-cuda -march=sm_70 {{.*}}.s {{.*}}.o
+
----------------
tra wrote:
> I'm puzzled about how exactly we're checking the `that we extract a static library defining an undefined symbol` part here.
> 
> Presumably the trailing .o would be the object extracted from the library. I'm not sure where the first .o/.s argument come from? Is that the 'main' GPU object/executable embedded in the host object?
> 
Yes, if we extract it we'll have two object files. The `.s` comes from the fact that I deliberately made the main binary an ELF while the library is a `.bc`. This is why we get a `.s` for Nvidia, it's PTX.

================
Comment at: clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp:1213
+
+    // We will extract if it defines a new global symbol visible to the host.
+    bool NewGlobalSymbol = ((NewSymbol || (OldSym & Sym_Undefined)) &&
----------------
tra wrote:
> Nit: perhaps we should rename `Resolved` -> `ShouldExtractObject`, it would be a better match. After all, defining/including a new symbol is not quite the same as resolving a reference.
Good point, I'll change it.

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https://reviews.llvm.org/D142484