[llvm] r176459 - Check isDiscardableIfUnused, rather than hasLocalLinkage, when bumping

[Lang Hames]

Thanks for the feedback. I think the duplication is fairly benign given the
proximity of the tests to one another, but I don't have strong feeling one
way or the other - please feel free to refactor if you think it would be an
improvement.

- Lang.


On Mon, Mar 4, 2013 at 2:53 PM, David Blaikie <dblaikie at gmail.com> wrote:

> On Mon, Mar 4, 2013 at 2:40 PM, Lang Hames <lhames at gmail.com> wrote:
> > Author: lhames
> > Date: Mon Mar  4 16:40:44 2013
> > New Revision: 176459
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=176459&view=rev
> > Log:
> > Check isDiscardableIfUnused, rather than hasLocalLinkage, when bumping
> > GlobalValue linkage up to ExternalLinkage in the ExtractGV pass. This
> > prevents linkonce and linkonce_odr symbols from being DCE'd.
> >
> > Added:
> >     llvm/trunk/test/Other/extract-linkonce.ll
> > Modified:
> >     llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp
> >
> > Modified: llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp?rev=176459&r1=176458&r2=176459&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp (original)
> > +++ llvm/trunk/lib/Transforms/IPO/ExtractGV.cpp Mon Mar  4 16:40:44 2013
> > @@ -60,7 +60,7 @@ namespace {
> >              continue;
> >          }
> >
> > -        bool Local = I->hasLocalLinkage();
> > +        bool Local = I->isDiscardableIfUnused();
> >          if (Local)
> >            I->setVisibility(GlobalValue::HiddenVisibility);
> >
> > @@ -80,7 +80,7 @@ namespace {
> >              continue;
> >          }
> >
> > -        bool Local = I->hasLocalLinkage();
> > +        bool Local = I->isDiscardableIfUnused();
> >          if (Local)
> >            I->setVisibility(GlobalValue::HiddenVisibility);
> >
> > @@ -97,7 +97,7 @@ namespace {
> >          Module::alias_iterator CurI = I;
> >          ++I;
> >
> > -        if (CurI->hasLocalLinkage()) {
> > +        if (CurI->isDiscardableIfUnused()) {
> >            CurI->setVisibility(GlobalValue::HiddenVisibility);
>
> Little bit of deja vu? Is there some refactoring that could be done to
> reduce the duplication in this code? (I haven't really looked in
> detail, just saw a patch with three rather similar changes to rather
> similar code)
>
> >            CurI->setLinkage(GlobalValue::ExternalLinkage);
> >          }
> >
> > Added: llvm/trunk/test/Other/extract-linkonce.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Other/extract-linkonce.ll?rev=176459&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/test/Other/extract-linkonce.ll (added)
> > +++ llvm/trunk/test/Other/extract-linkonce.ll Mon Mar  4 16:40:44 2013
> > @@ -0,0 +1,23 @@
> > +; RUN: llvm-extract -func foo -S < %s | FileCheck %s
> > +; RUN: llvm-extract -delete -func foo -S < %s | FileCheck
> --check-prefix=DELETE %s
> > +
> > +; Test that we don't convert weak_odr to external definitions.
> > +
> > +; CHECK:      @bar = external hidden global i32
> > +; CHECK:      define hidden i32* @foo() {
> > +; CHECK-NEXT:  ret i32* @bar
> > +; CHECK-NEXT: }
> > +
> > +; DELETE: @bar = hidden global i32 42
> > +; DELETE: declare hidden i32* @foo()
> > +
> > + at bar = linkonce global i32 42
> > +
> > +define linkonce i32* @foo() {
> > +  ret i32* @bar
> > +}
> > +
> > +define void @g() {
> > +  call i32* @foo()
> > +  ret void
> > +}
> >
> >
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>
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