<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Apr 20, 2015 at 1:59 PM, Duncan P. N. Exon Smith <span dir="ltr"><<a href="mailto:dexonsmith@apple.com" target="_blank">dexonsmith@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><br>
> On 2015-Apr-20, at 13:28, Luqman Aden <<a href="mailto:me%2Bllvm@luqman.ca">me+llvm@luqman.ca</a>> wrote:<br>
><br>
> From df1b11c561dc826d8e4836b9e910ac75185bcf05 Mon Sep 17 00:00:00 2001<br>
> From: Luqman Aden <<a href="mailto:luqman@apple.com">luqman@apple.com</a>><br>
> Date: Wed, 15 Apr 2015 12:22:32 -0700<br>
> Subject: [PATCH] llvm-link: Add -override flag to prefer one of a duplicate<br>
> symbol.<br>
><br>
> ---<br>
> include/llvm/Linker/Linker.h | 4 +++-<br>
> lib/Linker/LinkModules.cpp | 20 +++++++++++++++----<br>
> test/tools/llvm-link/Inputs/foo.ll | 4 ++++<br>
> test/tools/llvm-link/hello.ll | 20 +++++++++++++++++++<br>
> test/tools/llvm-link/lit.local.cfg | 1 +<br>
> tools/llvm-link/llvm-link.cpp | 40 ++++++++++++++++++++++++--------------<br>
> 6 files changed, 69 insertions(+), 20 deletions(-)<br>
> create mode 100644 test/tools/llvm-link/Inputs/foo.ll<br>
> create mode 100644 test/tools/llvm-link/hello.ll<br>
> create mode 100644 test/tools/llvm-link/lit.local.cfg<br>
><br>
<br>
> From df1b11c561dc826d8e4836b9e910ac75185bcf05 Mon Sep 17 00:00:00 2001<br>
> From: Luqman Aden <<a href="mailto:luqman@apple.com">luqman@apple.com</a>><br>
> Date: Wed, 15 Apr 2015 12:22:32 -0700<br>
> Subject: [PATCH] llvm-link: Add -override flag to prefer one of a duplicate<br>
> symbol.<br>
<br>
</span>Luqman and I talked in person, and he added some context for this (seems<br>
to still be missing from llvm-commits?). The idea is to support an LLVM<br>
developer workflow where a subset of the module is extracted to a side<br>
module to be manipulated or optimized differently. Sometime before<br>
CodeGen, these functions are merged back in, and should replace the<br>
copies in the "main" module (regardless of IR linkage types).<br>
<br>
This seems like a pretty useful debugging workflow to me, and the<br>
approach in this patch seems about right.<br>
<br>
@Rafael, I'd appreciate your opinion on this.<br>
<div><div class="h5"><br>
><br>
> ---<br>
> include/llvm/Linker/Linker.h | 4 +++-<br>
> lib/Linker/LinkModules.cpp | 20 +++++++++++++++----<br>
> test/tools/llvm-link/Inputs/foo.ll | 4 ++++<br>
> test/tools/llvm-link/hello.ll | 20 +++++++++++++++++++<br>
> test/tools/llvm-link/lit.local.cfg | 1 +<br>
> tools/llvm-link/llvm-link.cpp | 40 ++++++++++++++++++++++++--------------<br>
> 6 files changed, 69 insertions(+), 20 deletions(-)<br>
> create mode 100644 test/tools/llvm-link/Inputs/foo.ll<br>
> create mode 100644 test/tools/llvm-link/hello.ll<br>
> create mode 100644 test/tools/llvm-link/lit.local.cfg<br>
><br>
> diff --git a/include/llvm/Linker/Linker.h b/include/llvm/Linker/Linker.h<br>
> index 5ca815c..c43b90e 100644<br>
> --- a/include/llvm/Linker/Linker.h<br>
> +++ b/include/llvm/Linker/Linker.h<br>
> @@ -68,8 +68,10 @@ public:<br>
> void deleteModule();<br>
><br>
> /// \brief Link \p Src into the composite. The source is destroyed.<br>
> + /// Passing OverrideSymbols as true will have symbols from Src<br>
> + /// shadow those in the Dest.<br>
> /// Returns true on error.<br>
> - bool linkInModule(Module *Src);<br>
> + bool linkInModule(Module *Src, bool OverrideSymbols = false);<br>
><br>
> /// \brief Set the composite to the passed-in module.<br>
> void setModule(Module *Dst);<br>
> diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp<br>
> index 21edc50..3a46a33 100644<br>
> --- a/lib/Linker/LinkModules.cpp<br>
> +++ b/lib/Linker/LinkModules.cpp<br>
> @@ -424,12 +424,17 @@ class ModuleLinker {<br>
><br>
> DiagnosticHandlerFunction DiagnosticHandler;<br>
><br>
> + /// For symbol clashes, prefer those from Src.<br>
> + bool OverrideFromSrc;<br>
> +<br>
> public:<br>
> ModuleLinker(Module *dstM, Linker::IdentifiedStructTypeSet &Set, Module *srcM,<br>
> - DiagnosticHandlerFunction DiagnosticHandler)<br>
> + DiagnosticHandlerFunction DiagnosticHandler,<br>
> + bool Override = false)<br>
<br>
</div></div>Why spell this differently from the class member?<br>
<br>
Also, are there any callers that don't specify this flag? If not, don't<br>
provide a default.<br></blockquote><div><br></div><div>Updated.<br> <br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<span class=""><br>
> : DstM(dstM), SrcM(srcM), TypeMap(Set),<br>
> ValMaterializer(TypeMap, DstM, LazilyLinkGlobalValues),<br>
> - DiagnosticHandler(DiagnosticHandler) {}<br>
> + DiagnosticHandler(DiagnosticHandler),<br>
> + OverrideFromSrc(Override) {}<br>
><br>
> bool run();<br>
><br>
> @@ -725,6 +730,12 @@ bool ModuleLinker::getComdatResult(const Comdat *SrcC,<br>
> bool ModuleLinker::shouldLinkFromSource(bool &LinkFromSrc,<br>
> const GlobalValue &Dest,<br>
> const GlobalValue &Src) {<br>
> + // Should we unconditionally use the Src?<br>
> + if (OverrideFromSrc) {<br>
> + LinkFromSrc = true;<br>
> + return false;<br>
> + }<br>
> +<br>
> // We always have to add Src if it has appending linkage.<br>
> if (Src.hasAppendingLinkage()) {<br>
> LinkFromSrc = true;<br>
> @@ -794,6 +805,7 @@ bool ModuleLinker::shouldLinkFromSource(bool &LinkFromSrc,<br>
> assert(!Dest.hasExternalWeakLinkage());<br>
> assert(Dest.hasExternalLinkage() && Src.hasExternalLinkage() &&<br>
> "Unexpected linkage type!");<br>
> +<br>
<br>
</span>This seems unrelated to the patch?<br></blockquote><div><br></div><div>Yes, whitespace left over from debugging before. I've now removed it.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<span class=""><br>
> return emitError("Linking globals named '" + Src.getName() +<br>
> "': symbol multiply defined!");<br>
> }<br>
> @@ -1742,9 +1754,9 @@ void Linker::deleteModule() {<br>
> Composite = nullptr;<br>
> }<br>
><br>
> -bool Linker::linkInModule(Module *Src) {<br>
> +bool Linker::linkInModule(Module *Src, bool OverrideSymbols) {<br>
> ModuleLinker TheLinker(Composite, IdentifiedStructTypes, Src,<br>
> - DiagnosticHandler);<br>
> + DiagnosticHandler, OverrideSymbols);<br>
> bool RetCode = TheLinker.run();<br>
> Composite->dropTriviallyDeadConstantArrays();<br>
> return RetCode;<br>
> diff --git a/test/tools/llvm-link/Inputs/foo.ll b/test/tools/llvm-link/Inputs/foo.ll<br>
> new file mode 100644<br>
> index 0000000..6e06fa5<br>
> --- /dev/null<br>
> +++ b/test/tools/llvm-link/Inputs/foo.ll<br>
> @@ -0,0 +1,4 @@<br>
> +define i32 @foo(i32 %i) {<br>
> +entry:<br>
> + ret i32 4<br>
> +}<br>
<br>
</span>We usually put lib/Linker tests in "test/Linker".<br>
<span class=""><br>
> diff --git a/test/tools/llvm-link/hello.ll b/test/tools/llvm-link/hello.ll<br>
> new file mode 100644<br>
> index 0000000..c124864<br>
> --- /dev/null<br>
> +++ b/test/tools/llvm-link/hello.ll<br>
> @@ -0,0 +1,20 @@<br>
> +; RUN: llvm-as %s -o %t-hello.bc<br>
> +; RUN: llvm-as %p/Inputs/foo.ll -o %t-foo.bc<br>
<br>
</span>Why not just use llvm-link directly?<br></blockquote><div><br></div><div>I initially thought it wanted .bc only and just hadn't updated the test there.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Also, I recommend this naming scheme:<br>
<br>
test/Linker/manual-override.ll<br>
test/Linker/Inputs/manual-override.ll<br>
<br>
(Or whatever you want to name the tests, but I wouldn't call it "hello".)<br>
<br>
I'd also use `%S` instead of `%p`, since last I checked only the<br>
former is actually documented at <a href="http://llvm.org" target="_blank">llvm.org</a>.<br>
<br>
Also, it might be worth testing both command-line orderings.<br></blockquote><div><br></div><div>Added.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div class="h5"><br>
> +; RUN: llvm-link %t-hello.bc -override %t-foo.bc -S | FileCheck %s<br>
> +<br>
> +<br>
> +; CHECK-LABEL: define i32 @foo<br>
> +; CHECK-NEXT: entry:<br>
> +; CHECK-NEXT: ret i32 4<br>
> +define i32 @foo(i32 %i) {<br>
> +entry:<br>
> + %add = add nsw i32 %i, %i<br>
> + ret i32 %add<br>
> +}<br>
> +<br>
> +; Function Attrs: nounwind ssp uwtable<br>
> +define i32 @main(i32 %argc, i8** %argv) {<br>
> +entry:<br>
> + %a = call i32 @foo(i32 2)<br>
> + ret i32 %a<br>
> +}<br>
> diff --git a/test/tools/llvm-link/lit.local.cfg b/test/tools/llvm-link/lit.local.cfg<br>
> new file mode 100644<br>
> index 0000000..c6106e4<br>
> --- /dev/null<br>
> +++ b/test/tools/llvm-link/lit.local.cfg<br>
> @@ -0,0 +1 @@<br>
> +config.suffixes = ['.ll']<br>
<br>
</div></div>Since the tests should probably be moved to `test/Linker`, we probably<br>
don't need this.<br>
<div><div class="h5"><br>
> diff --git a/tools/llvm-link/llvm-link.cpp b/tools/llvm-link/llvm-link.cpp<br>
> index 6924aa5..54d49f5 100644<br>
> --- a/tools/llvm-link/llvm-link.cpp<br>
> +++ b/tools/llvm-link/llvm-link.cpp<br>
> @@ -38,6 +38,11 @@ static cl::list<std::string><br>
> InputFilenames(cl::Positional, cl::OneOrMore,<br>
> cl::desc("<input bitcode files>"));<br>
><br>
> +static cl::list<std::string><br>
> +OverridingInputs("override", cl::ZeroOrMore, cl::value_desc("filename"),<br>
> + cl::desc("input bitcode file which can "<br>
> + "override previously defined symbol"));<br>
> +<br>
> static cl::opt<std::string><br>
> OutputFilename("o", cl::desc("Override output filename"), cl::init("-"),<br>
> cl::value_desc("filename"));<br>
> @@ -109,24 +114,29 @@ int main(int argc, char **argv) {<br>
> auto Composite = make_unique<Module>("llvm-link", Context);<br>
> Linker L(Composite.get(), diagnosticHandler);<br>
><br>
> - for (unsigned i = 0; i < InputFilenames.size(); ++i) {<br>
> - std::unique_ptr<Module> M = loadFile(argv[0], InputFilenames[i], Context);<br>
> - if (!M.get()) {<br>
> - errs() << argv[0] << ": error loading file '" <<InputFilenames[i]<< "'\n";<br>
> - return 1;<br>
> - }<br>
> + auto linkFiles = [&](const cl::list<std::string>& Files, bool Override) {<br>
> + for (auto File : Files) {<br>
> + std::unique_ptr<Module> M = loadFile(argv[0], File, Context);<br>
> + if (!M.get()) {<br>
> + errs() << argv[0] << ": error loading file '" << File << "'\n";<br>
> + exit(1);<br>
> + }<br>
><br>
> - if (verifyModule(*M, &errs())) {<br>
> - errs() << argv[0] << ": " << InputFilenames[i]<br>
> - << ": error: input module is broken!\n";<br>
> - return 1;<br>
> - }<br>
> + if (verifyModule(*M, &errs())) {<br>
> + errs() << argv[0] << ": " << File<br>
> + << ": error: input module is broken!\n";<br>
> + exit(1);<br>
> + }<br>
><br>
> - if (Verbose) errs() << "Linking in '" << InputFilenames[i] << "'\n";<br>
> + if (Verbose) errs() << "Linking in '" << File << "'\n";<br>
><br>
> - if (L.linkInModule(M.get()))<br>
> - return 1;<br>
> - }<br>
> + if (L.linkInModule(M.get(), Override))<br>
> + exit(1);<br>
> + }<br>
> + };<br>
> +<br>
> + linkFiles(InputFilenames, false);<br>
<br>
</div></div>It'd be nice for the refactoring part of this (i.e., the part that<br>
changes all the indentation) to be in a separate NFC (no functionality<br>
change) commit so it's easier to see what has really changed.<br></blockquote><div><br></div><div>Done.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="HOEnZb"><div class="h5"><br>
> + linkFiles(OverridingInputs, true);<br>
><br>
> if (DumpAsm) errs() << "Here's the assembly:\n" << *Composite;<br>
><br>
> --<br>
> 2.3.0 (Apple Git-54)<br>
><br>
><br>
<br>
</div></div></blockquote></div><br><br><br></div></div>