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[NvlinkWrapper] Add support for --undefined (#113934)

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Summary:
This flag is pretty canonical in ELF linkers, it allows us to force the
link job to extract a library if it defines a specific symbol. This is
mostly useful for letting us forcibly extract things that don't fit the
normal model (i.e. kernels) from static libraries.
This commit is contained in:
Joseph Huber
2024-10-29 13:34:28 -07:00
committed by GitHub
parent 8193832fb9
commit a78861fc55
3 changed files with 18 additions and 5 deletions
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13
clang/test/Driver/nvlink-wrapper.c
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@@ -21,12 +21,13 @@ int bar() {
}
#else
extern int y;
int __attribute__((visibility("hidden"))) x = 999;
extern int x;
int baz() { return y + x; }
#endif
// Create various inputs to test basic linking and LTO capabilities. Creating a
// CUDA binary requires access to the `ptxas` executable, so we just use x64.
// RUN: %clang -cc1 %s -triple nvptx64-nvidia-cuda -emit-llvm-bc -o %t.o
// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -DX -o %t-x.o
// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -DY -o %t-y.o
// RUN: %clang -cc1 %s -triple x86_64-unknown-linux-gnu -emit-obj -DZ -o %t-z.o
@@ -36,6 +37,7 @@ int baz() { return y + x; }
// RUN: llvm-ar rcs %t-y.a %t-y.o
// RUN: llvm-ar rcs %t-z.a %t-z.o
// RUN: llvm-ar rcs %t-w.a %t-w.o
// RUN: llvm-ar rcs %t-u.a %t-u.o
//
// Check that we forward any unrecognized argument to 'nvlink'.
@@ -49,11 +51,16 @@ int baz() { return y + x; }
// `libx.a` and `liby.a` because extern weak symbols do not extract and `libz.a`
// is not used at all.
//
// RUN: clang-nvlink-wrapper --dry-run %t-x.a %t-u.o %t-y.a %t-z.a %t-w.a \
// RUN: clang-nvlink-wrapper --dry-run %t-x.a %t-u.a %t-y.a %t-z.a %t-w.a %t.o \
// RUN: -arch sm_52 -o a.out 2>&1 | FileCheck %s --check-prefix=LINK
// LINK: nvlink{{.*}} -arch sm_52 -o a.out [[INPUT:.+]].cubin {{.*}}-x-{{.*}}.cubin{{.*}}-y-{{.*}}.cubin
// RUN: %clang -cc1 %s -triple nvptx64-nvidia-cuda -emit-llvm-bc -o %t.o
//
// Same as above but we use '--undefined' to forcibly extract 'libz.a'
//
// RUN: clang-nvlink-wrapper --dry-run %t-x.a %t-u.a %t-y.a %t-z.a %t-w.a %t.o \
// RUN: -u z -arch sm_52 -o a.out 2>&1 | FileCheck %s --check-prefix=LINK
// UNDEFINED: nvlink{{.*}} -arch sm_52 -o a.out [[INPUT:.+]].cubin {{.*}}-x-{{.*}}.cubin{{.*}}-y-{{.*}}.cubin{{.*}}-z-{{.*}}.cubin
//
// Check that the LTO interface works and properly preserves symbols used in a

3
clang/tools/clang-nvlink-wrapper/ClangNVLinkWrapper.cpp
View File

@@ -250,6 +250,7 @@ struct Symbol {
};
Symbol() : File(), Flags(None), UsedInRegularObj(false) {}
Symbol(Symbol::Flags Flags) : File(), Flags(Flags), UsedInRegularObj(true) {}
Symbol(MemoryBufferRef File, const irsymtab::Reader::SymbolRef Sym)
: File(File), Flags(0), UsedInRegularObj(false) {
@@ -535,6 +536,8 @@ Expected<SmallVector<StringRef>> getInput(const ArgList &Args) {
bool Extracted = true;
StringMap<Symbol> SymTab;
for (auto &Sym : Args.getAllArgValues(OPT_u))
SymTab[Sym] = Symbol(Symbol::Undefined);
SmallVector<std::unique_ptr<MemoryBuffer>> LinkerInput;
while (Extracted) {
Extracted = false;

7
clang/tools/clang-nvlink-wrapper/NVLinkOpts.td
View File

@@ -43,11 +43,11 @@ def plugin : JoinedOrSeparate<["--", "-"], "plugin">,
Flags<[HelpHidden, WrapperOnlyOption]>;
def arch : Separate<["--", "-"], "arch">,
HelpText<"Specify the 'sm_' name of the target architecture.">;
HelpText<"Specify the 'sm_' name of the target architecture">;
def : Joined<["--", "-"], "plugin-opt=mcpu=">,
Flags<[HelpHidden, WrapperOnlyOption]>, Alias<arch>;
def g : Flag<["-"], "g">, HelpText<"Specify that this was a debug compile.">;
def g : Flag<["-"], "g">, HelpText<"Specify that this was a debug compile">;
def debug : Flag<["--"], "debug">, Alias<g>;
def lto_emit_llvm : Flag<["--"], "lto-emit-llvm">, Flags<[WrapperOnlyOption]>,
@@ -55,6 +55,9 @@ def lto_emit_llvm : Flag<["--"], "lto-emit-llvm">, Flags<[WrapperOnlyOption]>,
def lto_emit_asm : Flag<["--"], "lto-emit-asm">, Flags<[WrapperOnlyOption]>,
HelpText<"Emit assembly code">;
def u : JoinedOrSeparate<["-"], "u">, HelpText<"Force undefined symbol during linking">;
def undefined : JoinedOrSeparate<["--"], "undefined">, Alias<u>;
def O : Joined<["--", "-"], "plugin-opt=O">,
Flags<[WrapperOnlyOption]>, MetaVarName<"<O0, O1, O2, or O3>">,
HelpText<"Optimization level for LTO">;