[PATCH] llvm-link: Add -override flag to prefer duplicate symbols from one module.
Luqman Aden
me+llvm at luqman.ca
Tue Apr 21 17:31:08 PDT 2015
On Tue, Apr 21, 2015 at 3:42 PM, Duncan P. N. Exon Smith <
dexonsmith at apple.com> wrote:
>
> > On 2015-Apr-20, at 15:07, Luqman Aden <me+llvm at luqman.ca> wrote:
> >
> >
> >
> > On Mon, Apr 20, 2015 at 1:59 PM, Duncan P. N. Exon Smith <
> dexonsmith at apple.com> wrote:
> >
> > > On 2015-Apr-20, at 13:28, Luqman Aden <me+llvm at luqman.ca> wrote:
> > >
> > > From df1b11c561dc826d8e4836b9e910ac75185bcf05 Mon Sep 17 00:00:00 2001
> > > From: Luqman Aden <luqman at apple.com>
> > > Date: Wed, 15 Apr 2015 12:22:32 -0700
> > > Subject: [PATCH] llvm-link: Add -override flag to prefer one of a
> duplicate
> > > symbol.
> > >
> > > ---
> > > include/llvm/Linker/Linker.h | 4 +++-
> > > lib/Linker/LinkModules.cpp | 20 +++++++++++++++----
> > > test/tools/llvm-link/Inputs/foo.ll | 4 ++++
> > > test/tools/llvm-link/hello.ll | 20 +++++++++++++++++++
> > > test/tools/llvm-link/lit.local.cfg | 1 +
> > > tools/llvm-link/llvm-link.cpp | 40
> ++++++++++++++++++++++++--------------
> > > 6 files changed, 69 insertions(+), 20 deletions(-)
> > > create mode 100644 test/tools/llvm-link/Inputs/foo.ll
> > > create mode 100644 test/tools/llvm-link/hello.ll
> > > create mode 100644 test/tools/llvm-link/lit.local.cfg
> > >
> >
> > > From df1b11c561dc826d8e4836b9e910ac75185bcf05 Mon Sep 17 00:00:00 2001
> > > From: Luqman Aden <luqman at apple.com>
> > > Date: Wed, 15 Apr 2015 12:22:32 -0700
> > > Subject: [PATCH] llvm-link: Add -override flag to prefer one of a
> duplicate
> > > symbol.
> >
> > Luqman and I talked in person, and he added some context for this (seems
> > to still be missing from llvm-commits?). The idea is to support an LLVM
> > developer workflow where a subset of the module is extracted to a side
> > module to be manipulated or optimized differently. Sometime before
> > CodeGen, these functions are merged back in, and should replace the
> > copies in the "main" module (regardless of IR linkage types).
> >
> > This seems like a pretty useful debugging workflow to me, and the
> > approach in this patch seems about right.
> >
> > @Rafael, I'd appreciate your opinion on this.
> >
> > >
> > > ---
> > > include/llvm/Linker/Linker.h | 4 +++-
> > > lib/Linker/LinkModules.cpp | 20 +++++++++++++++----
> > > test/tools/llvm-link/Inputs/foo.ll | 4 ++++
> > > test/tools/llvm-link/hello.ll | 20 +++++++++++++++++++
> > > test/tools/llvm-link/lit.local.cfg | 1 +
> > > tools/llvm-link/llvm-link.cpp | 40
> ++++++++++++++++++++++++--------------
> > > 6 files changed, 69 insertions(+), 20 deletions(-)
> > > create mode 100644 test/tools/llvm-link/Inputs/foo.ll
> > > create mode 100644 test/tools/llvm-link/hello.ll
> > > create mode 100644 test/tools/llvm-link/lit.local.cfg
> > >
> > > diff --git a/include/llvm/Linker/Linker.h
> b/include/llvm/Linker/Linker.h
> > > index 5ca815c..c43b90e 100644
> > > --- a/include/llvm/Linker/Linker.h
> > > +++ b/include/llvm/Linker/Linker.h
> > > @@ -68,8 +68,10 @@ public:
> > > void deleteModule();
> > >
> > > /// \brief Link \p Src into the composite. The source is destroyed.
> > > + /// Passing OverrideSymbols as true will have symbols from Src
> > > + /// shadow those in the Dest.
> > > /// Returns true on error.
> > > - bool linkInModule(Module *Src);
> > > + bool linkInModule(Module *Src, bool OverrideSymbols = false);
> > >
> > > /// \brief Set the composite to the passed-in module.
> > > void setModule(Module *Dst);
> > > diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
> > > index 21edc50..3a46a33 100644
> > > --- a/lib/Linker/LinkModules.cpp
> > > +++ b/lib/Linker/LinkModules.cpp
> > > @@ -424,12 +424,17 @@ class ModuleLinker {
> > >
> > > DiagnosticHandlerFunction DiagnosticHandler;
> > >
> > > + /// For symbol clashes, prefer those from Src.
> > > + bool OverrideFromSrc;
> > > +
> > > public:
> > > ModuleLinker(Module *dstM, Linker::IdentifiedStructTypeSet &Set,
> Module *srcM,
> > > - DiagnosticHandlerFunction DiagnosticHandler)
> > > + DiagnosticHandlerFunction DiagnosticHandler,
> > > + bool Override = false)
> >
> > Why spell this differently from the class member?
> >
> > Also, are there any callers that don't specify this flag? If not, don't
> > provide a default.
> >
> > Updated.
> >
> >
> > > : DstM(dstM), SrcM(srcM), TypeMap(Set),
> > > ValMaterializer(TypeMap, DstM, LazilyLinkGlobalValues),
> > > - DiagnosticHandler(DiagnosticHandler) {}
> > > + DiagnosticHandler(DiagnosticHandler),
> > > + OverrideFromSrc(Override) {}
> > >
> > > bool run();
> > >
> > > @@ -725,6 +730,12 @@ bool ModuleLinker::getComdatResult(const Comdat
> *SrcC,
> > > bool ModuleLinker::shouldLinkFromSource(bool &LinkFromSrc,
> > > const GlobalValue &Dest,
> > > const GlobalValue &Src) {
> > > + // Should we unconditionally use the Src?
> > > + if (OverrideFromSrc) {
> > > + LinkFromSrc = true;
> > > + return false;
> > > + }
> > > +
> > > // We always have to add Src if it has appending linkage.
> > > if (Src.hasAppendingLinkage()) {
> > > LinkFromSrc = true;
> > > @@ -794,6 +805,7 @@ bool ModuleLinker::shouldLinkFromSource(bool
> &LinkFromSrc,
> > > assert(!Dest.hasExternalWeakLinkage());
> > > assert(Dest.hasExternalLinkage() && Src.hasExternalLinkage() &&
> > > "Unexpected linkage type!");
> > > +
> >
> > This seems unrelated to the patch?
> >
> > Yes, whitespace left over from debugging before. I've now removed it.
> >
> >
> > > return emitError("Linking globals named '" + Src.getName() +
> > > "': symbol multiply defined!");
> > > }
> > > @@ -1742,9 +1754,9 @@ void Linker::deleteModule() {
> > > Composite = nullptr;
> > > }
> > >
> > > -bool Linker::linkInModule(Module *Src) {
> > > +bool Linker::linkInModule(Module *Src, bool OverrideSymbols) {
> > > ModuleLinker TheLinker(Composite, IdentifiedStructTypes, Src,
> > > - DiagnosticHandler);
> > > + DiagnosticHandler, OverrideSymbols);
> > > bool RetCode = TheLinker.run();
> > > Composite->dropTriviallyDeadConstantArrays();
> > > return RetCode;
> > > diff --git a/test/tools/llvm-link/Inputs/foo.ll
> b/test/tools/llvm-link/Inputs/foo.ll
> > > new file mode 100644
> > > index 0000000..6e06fa5
> > > --- /dev/null
> > > +++ b/test/tools/llvm-link/Inputs/foo.ll
> > > @@ -0,0 +1,4 @@
> > > +define i32 @foo(i32 %i) {
> > > +entry:
> > > + ret i32 4
> > > +}
> >
> > We usually put lib/Linker tests in "test/Linker".
> >
> > > diff --git a/test/tools/llvm-link/hello.ll
> b/test/tools/llvm-link/hello.ll
> > > new file mode 100644
> > > index 0000000..c124864
> > > --- /dev/null
> > > +++ b/test/tools/llvm-link/hello.ll
> > > @@ -0,0 +1,20 @@
> > > +; RUN: llvm-as %s -o %t-hello.bc
> > > +; RUN: llvm-as %p/Inputs/foo.ll -o %t-foo.bc
> >
> > Why not just use llvm-link directly?
> >
> > I initially thought it wanted .bc only and just hadn't updated the test
> there.
> >
> >
> > Also, I recommend this naming scheme:
> >
> > test/Linker/manual-override.ll
> > test/Linker/Inputs/manual-override.ll
> >
> > (Or whatever you want to name the tests, but I wouldn't call it "hello".)
> >
> > I'd also use `%S` instead of `%p`, since last I checked only the
> > former is actually documented at llvm.org.
> >
> > Also, it might be worth testing both command-line orderings.
> >
> > Added.
> >
> >
> > > +; RUN: llvm-link %t-hello.bc -override %t-foo.bc -S | FileCheck %s
> > > +
> > > +
> > > +; CHECK-LABEL: define i32 @foo
> > > +; CHECK-NEXT: entry:
> > > +; CHECK-NEXT: ret i32 4
> > > +define i32 @foo(i32 %i) {
> > > +entry:
> > > + %add = add nsw i32 %i, %i
> > > + ret i32 %add
> > > +}
> > > +
> > > +; Function Attrs: nounwind ssp uwtable
> > > +define i32 @main(i32 %argc, i8** %argv) {
> > > +entry:
> > > + %a = call i32 @foo(i32 2)
> > > + ret i32 %a
> > > +}
> > > diff --git a/test/tools/llvm-link/lit.local.cfg
> b/test/tools/llvm-link/lit.local.cfg
> > > new file mode 100644
> > > index 0000000..c6106e4
> > > --- /dev/null
> > > +++ b/test/tools/llvm-link/lit.local.cfg
> > > @@ -0,0 +1 @@
> > > +config.suffixes = ['.ll']
> >
> > Since the tests should probably be moved to `test/Linker`, we probably
> > don't need this.
> >
> > > diff --git a/tools/llvm-link/llvm-link.cpp
> b/tools/llvm-link/llvm-link.cpp
> > > index 6924aa5..54d49f5 100644
> > > --- a/tools/llvm-link/llvm-link.cpp
> > > +++ b/tools/llvm-link/llvm-link.cpp
> > > @@ -38,6 +38,11 @@ static cl::list<std::string>
> > > InputFilenames(cl::Positional, cl::OneOrMore,
> > > cl::desc("<input bitcode files>"));
> > >
> > > +static cl::list<std::string>
> > > +OverridingInputs("override", cl::ZeroOrMore,
> cl::value_desc("filename"),
> > > + cl::desc("input bitcode file which can "
> > > + "override previously defined symbol"));
> > > +
> > > static cl::opt<std::string>
> > > OutputFilename("o", cl::desc("Override output filename"),
> cl::init("-"),
> > > cl::value_desc("filename"));
> > > @@ -109,24 +114,29 @@ int main(int argc, char **argv) {
> > > auto Composite = make_unique<Module>("llvm-link", Context);
> > > Linker L(Composite.get(), diagnosticHandler);
> > >
> > > - for (unsigned i = 0; i < InputFilenames.size(); ++i) {
> > > - std::unique_ptr<Module> M = loadFile(argv[0], InputFilenames[i],
> Context);
> > > - if (!M.get()) {
> > > - errs() << argv[0] << ": error loading file '"
> <<InputFilenames[i]<< "'\n";
> > > - return 1;
> > > - }
> > > + auto linkFiles = [&](const cl::list<std::string>& Files, bool
> Override) {
> > > + for (auto File : Files) {
> > > + std::unique_ptr<Module> M = loadFile(argv[0], File, Context);
> > > + if (!M.get()) {
> > > + errs() << argv[0] << ": error loading file '" << File <<
> "'\n";
> > > + exit(1);
> > > + }
> > >
> > > - if (verifyModule(*M, &errs())) {
> > > - errs() << argv[0] << ": " << InputFilenames[i]
> > > - << ": error: input module is broken!\n";
> > > - return 1;
> > > - }
> > > + if (verifyModule(*M, &errs())) {
> > > + errs() << argv[0] << ": " << File
> > > + << ": error: input module is broken!\n";
> > > + exit(1);
> > > + }
> > >
> > > - if (Verbose) errs() << "Linking in '" << InputFilenames[i] <<
> "'\n";
> > > + if (Verbose) errs() << "Linking in '" << File << "'\n";
> > >
> > > - if (L.linkInModule(M.get()))
> > > - return 1;
> > > - }
> > > + if (L.linkInModule(M.get(), Override))
> > > + exit(1);
> > > + }
> > > + };
> > > +
> > > + linkFiles(InputFilenames, false);
> >
> > It'd be nice for the refactoring part of this (i.e., the part that
> > changes all the indentation) to be in a separate NFC (no functionality
> > change) commit so it's easier to see what has really changed.
> >
> > Done.
>
> Ah, but the order seems wrong.
>
> In this case, anyway, putting the NFC commit first gives you two
> distinct changes: (1) refactor to make the code reusable, (2) actually
> reuse the code, adding a flag and condition, etc. Each commit stands
> on its own and is easy to post-commit review (first commit, refactoring
> noise; second commit, small functional change).
>
> The order you chose (NFC second) adds the duplicate/different code and
> then cleans it up. The first patch -- the one with real changes -- is
> *bigger* than your original patch, whereas my goal was to minimize the
> noise around the functional changes. Please reverse the commits.
>
Swapped the order of the commits.
>
> > + auto linkFiles = [&](const cl::list<std::string>& Files, bool
> Override) {
>
> Since I've gotten all nit-picky here anyway... I wonder whether using a
> lambda function is actually useful here. It saves passing `argv[0]` and
> `Context`, but I'm not sure that's buying much over just creating a
> normal `static` function. The latter seems just as clear, or maybe even
> clearer. I don't have a strong opinion; it's up to you.
>
Switched to a static function since that's what the rest of the code seems
to
be doing.
>
> > Subject: [PATCH 1/2] [llvm-link] Add -override flag to prefer one of a
> > duplicate symbol.
>
> Since you've attached patches from git, I've had a look at the commit
> messages, and the functional one in particular doesn't really explain
> the motivation.
>
> When you actually commit this you should describe the workflow that
> you're planning to use this in, or otherwise explain why this flag is
> useful.
>
> (Do you have commit access? If not, let me know when you send the next
> version of the patch and I'll commit it for you. In that case I can
> just reuse my own writeup from earlier in the thread if you want.)
>
No, I don't have commit access so that'd be great!
>
> > ---
> > include/llvm/Linker/Linker.h | 4 +++-
> > lib/Linker/LinkModules.cpp | 19 +++++++++++++++----
> > test/Linker/Inputs/manual-override.ll | 4 ++++
> > test/Linker/manual-override.ll | 19 +++++++++++++++++++
> > tools/llvm-link/llvm-link.cpp | 26 +++++++++++++++++++++++++-
>
> The testcases look a little light. Can you confirm what should happen
> if the linkage types differ? For example, if the -override is `linkonce`
> and the normal function is `weak`, IIUC the code will choose the
> `linkonce` function (thusly ignoring linkage rules). This makes sense to
> me -- that's what -override sounds like it should do -- but you should
> test it.
>
Added.
>
> Also, a test confirming that functions with `internal` linkage are
> unaffected makes sense to me. I.e., if you have `internal foo` in the
> main file, and normal (external) linkage in the -override file, the
> `internal foo` should be renamed out of the way instead of replaced.
> Similarly, an `internal foo` from the -override file should get renamed
> on collisions. (It looks like this is what will happen already, and it
> seems right to me, but I think it deserves a test.)
>
These too, but I did have to make one more small change to lib/Linker
to get the latter case working. Otherwise it would just ignore the internal
symbol from the -override input.
>
> Finally, one whitespace bug below:
>
> > diff --git a/tools/llvm-link/llvm-link.cpp
> b/tools/llvm-link/llvm-link.cpp
> > index 485a7b2..54d49f5 100644
> > --- a/tools/llvm-link/llvm-link.cpp
> > +++ b/tools/llvm-link/llvm-link.cpp
> > @@ -114,43 +114,29 @@ int main(int argc, char **argv) {
> > auto Composite = make_unique<Module>("llvm-link", Context);
> > Linker L(Composite.get(), diagnosticHandler);
> >
> > - for (unsigned i = 0; i < InputFilenames.size(); ++i) {
> > - std::unique_ptr<Module> M = loadFile(argv[0], InputFilenames[i],
> Context);
> > - if (!M.get()) {
> > - errs() << argv[0] << ": error loading file '"
> <<InputFilenames[i]<< "'\n";
> > - return 1;
> > + auto linkFiles = [&](const cl::list<std::string>& Files, bool
> Override) {
>
> `const cl::list<std::string>& Files` should be
> `const cl::list<std::string> &Files`. I recommend adding clang-format-diff
> to your workflow:
>
> http://clang.llvm.org/docs/ClangFormat.html#script-for-patch-reformatting
Ah cool, thanks!
>
>
> > + for (auto File : Files) {
> > + std::unique_ptr<Module> M = loadFile(argv[0], File, Context);
> > + if (!M.get()) {
> > + errs() << argv[0] << ": error loading file '" << File << "'\n";
> > + exit(1);
> > + }
> >
>
>
> > > + linkFiles(OverridingInputs, true);
> > >
> > > if (DumpAsm) errs() << "Here's the assembly:\n" << *Composite;
> > >
> > > --
> > > 2.3.0 (Apple Git-54)
> > >
> > >
> >
> >
> >
> >
> >
> <0001-llvm-link-Add-override-flag-to-prefer-one-of-a-dupli.patch><0002-llvm-link-Factor-out-code-for-handling-regular-and-o.patch>
>
>
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