[llvm] r254170 - Disallow aliases to available_externally.
Teresa Johnson via llvm-commits
llvm-commits at lists.llvm.org
Fri Nov 27 07:52:05 PST 2015
On Thu, Nov 26, 2015 at 11:22 AM, Rafael Espindola via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: rafael
> Date: Thu Nov 26 13:22:59 2015
> New Revision: 254170
>
> URL: http://llvm.org/viewvc/llvm-project?rev=254170&view=rev
> Log:
> Disallow aliases to available_externally.
>
> They are as much trouble as aliases to declarations. They are requiring
> the code generator to define a symbol with the same value as another
> symbol, but the second symbol is undefined.
Are any of these slipping through to codegen? I thought the
EliminateAvailableExternally pass should remove them all before that
point.
Teresa
>
> If representing this is important for some optimization, we could add
> support for available_externally aliases. They would be *required* to
> point to a declaration (or available_externally definition).
>
> Modified:
> llvm/trunk/lib/IR/Verifier.cpp
> llvm/trunk/lib/Linker/LinkModules.cpp
> llvm/trunk/lib/Transforms/IPO/ElimAvailExtern.cpp
> llvm/trunk/test/Linker/funcimport.ll
> llvm/trunk/test/Transforms/FunctionImport/funcimport.ll
> llvm/trunk/test/Verifier/alias.ll
>
> Modified: llvm/trunk/lib/IR/Verifier.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Verifier.cpp?rev=254170&r1=254169&r2=254170&view=diff
> ==============================================================================
> --- llvm/trunk/lib/IR/Verifier.cpp (original)
> +++ llvm/trunk/lib/IR/Verifier.cpp Thu Nov 26 13:22:59 2015
> @@ -571,7 +571,8 @@ void Verifier::visitAliaseeSubExpr(const
> void Verifier::visitAliaseeSubExpr(SmallPtrSetImpl<const GlobalAlias*> &Visited,
> const GlobalAlias &GA, const Constant &C) {
> if (const auto *GV = dyn_cast<GlobalValue>(&C)) {
> - Assert(!GV->isDeclaration(), "Alias must point to a definition", &GA);
> + Assert(!GV->isDeclarationForLinker(), "Alias must point to a definition",
> + &GA);
>
> if (const auto *GA2 = dyn_cast<GlobalAlias>(GV)) {
> Assert(Visited.insert(GA2).second, "Aliases cannot form a cycle", &GA);
>
> Modified: llvm/trunk/lib/Linker/LinkModules.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/LinkModules.cpp?rev=254170&r1=254169&r2=254170&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Linker/LinkModules.cpp (original)
> +++ llvm/trunk/lib/Linker/LinkModules.cpp Thu Nov 26 13:22:59 2015
> @@ -655,7 +655,10 @@ bool ModuleLinker::doImportAsDefinition(
> if (GA) {
> if (GA->hasWeakAnyLinkage())
> return false;
> - return doImportAsDefinition(GA->getBaseObject());
> + const GlobalObject *GO = GA->getBaseObject();
> + if (!GO->hasLinkOnceODRLinkage())
> + return false;
> + return doImportAsDefinition(GO);
> }
> // Always import GlobalVariable definitions, except for the special
> // case of WeakAny which are imported as ExternalWeak declarations
>
> Modified: llvm/trunk/lib/Transforms/IPO/ElimAvailExtern.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/ElimAvailExtern.cpp?rev=254170&r1=254169&r2=254170&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/IPO/ElimAvailExtern.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/ElimAvailExtern.cpp Thu Nov 26 13:22:59 2015
> @@ -49,46 +49,9 @@ ModulePass *llvm::createEliminateAvailab
> return new EliminateAvailableExternally();
> }
>
> -static void convertAliasToDeclaration(GlobalAlias &GA, Module &M) {
> - GlobalValue *GVal = GA.getBaseObject();
> - GlobalValue *NewGV;
> - if (auto *GVar = dyn_cast<GlobalVariable>(GVal)) {
> - GlobalVariable *NewGVar = new GlobalVariable(
> - M, GVar->getType()->getElementType(), GVar->isConstant(),
> - GVar->getLinkage(), /*init*/ nullptr, GA.getName(), GVar,
> - GVar->getThreadLocalMode(), GVar->getType()->getAddressSpace());
> - NewGV = NewGVar;
> - NewGV->copyAttributesFrom(GVar);
> - } else {
> - auto *F = dyn_cast<Function>(GVal);
> - assert(F);
> - Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
> - GA.getName(), &M);
> - NewGV = NewF;
> - NewGV->copyAttributesFrom(F);
> - }
> - GA.replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, GA.getType()));
> - GA.eraseFromParent();
> -}
> -
> bool EliminateAvailableExternally::runOnModule(Module &M) {
> bool Changed = false;
>
> - // Convert any aliases that alias with an available externally
> - // value (which will be turned into declarations later on in this routine)
> - // into declarations themselves. All aliases must be definitions, and
> - // must alias with a definition. So this involves creating a declaration
> - // equivalent to the alias's base object.
> - for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E;) {
> - // Increment the iterator first since we may delete the current alias.
> - GlobalAlias &GA = *(I++);
> - GlobalValue *GVal = GA.getBaseObject();
> - if (!GVal->hasAvailableExternallyLinkage())
> - continue;
> - convertAliasToDeclaration(GA, M);
> - Changed = true;
> - }
> -
> // Drop initializers of available externally global variables.
> for (GlobalVariable &GV : M.globals()) {
> if (!GV.hasAvailableExternallyLinkage())
>
> Modified: llvm/trunk/test/Linker/funcimport.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Linker/funcimport.ll?rev=254170&r1=254169&r2=254170&view=diff
> ==============================================================================
> --- llvm/trunk/test/Linker/funcimport.ll (original)
> +++ llvm/trunk/test/Linker/funcimport.ll Thu Nov 26 13:22:59 2015
> @@ -36,7 +36,7 @@
> ; turned into a declaration, but that strong alias to an imported function
> ; is imported as alias.
> ; RUN: llvm-link %t2.bc -functionindex=%t3.thinlto.bc -import=globalfunc2:%t.bc -S | FileCheck %s --check-prefix=IMPORTGLOB2
> -; IMPORTGLOB2-DAG: @analias = alias void (...), bitcast (void ()* @globalfunc2
> +; IMPORTGLOB2-DAG: declare void @analias()
> ; IMPORTGLOB2-DAG: declare void @globalfunc1
> ; IMPORTGLOB2-DAG: define available_externally void @globalfunc2
> ; IMPORTGLOB2-DAG: declare extern_weak void @weakalias
> @@ -44,7 +44,7 @@
> ; Ensure that strong alias imported in second pass of importing ends up
> ; as an alias.
> ; RUN: llvm-link %t2.bc -functionindex=%t3.thinlto.bc -import=globalfunc1:%t.bc -import=globalfunc2:%t.bc -S | FileCheck %s --check-prefix=IMPORTGLOB3
> -; IMPORTGLOB3-DAG: @analias = alias void (...), bitcast (void ()* @globalfunc2
> +; IMPORTGLOB3-DAG: declare void @analias()
> ; IMPORTGLOB3-DAG: define available_externally void @globalfunc1
> ; IMPORTGLOB3-DAG: define available_externally void @globalfunc2
> ; IMPORTGLOB3-DAG: declare extern_weak void @weakalias
> @@ -53,11 +53,17 @@
> ; as an alias, and that seeing the alias definition during a second inlining
> ; pass is handled correctly.
> ; RUN: llvm-link %t2.bc -functionindex=%t3.thinlto.bc -import=globalfunc2:%t.bc -import=globalfunc1:%t.bc -S | FileCheck %s --check-prefix=IMPORTGLOB4
> -; IMPORTGLOB4-DAG: @analias = alias void (...), bitcast (void ()* @globalfunc2
> +; IMPORTGLOB4-DAG: declare void @analias()
> ; IMPORTGLOB4-DAG: define available_externally void @globalfunc2
> ; IMPORTGLOB4-DAG: define available_externally void @globalfunc1
> ; IMPORTGLOB4-DAG: declare extern_weak void @weakalias
>
> +; An alias to an imported function is imported as alias if the function is not
> +; available_externally.
> +; RUN: llvm-link %t2.bc -functionindex=%t3.thinlto.bc -import=linkoncefunc:%t.bc -S | FileCheck %s --check-prefix=IMPORTGLOB5
> +; IMPORTGLOB5-DAG: linkoncealias = alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
> +; IMPORTGLOB5-DAG: define linkonce_odr void @linkoncefunc()
> +
> ; Ensure that imported static variable and function references are correctly
> ; promoted and renamed (including static constant variable).
> ; RUN: llvm-link %t2.bc -functionindex=%t3.thinlto.bc -import=referencestatics:%t.bc -S | FileCheck %s --check-prefix=IMPORTSTATIC
>
> Modified: llvm/trunk/test/Transforms/FunctionImport/funcimport.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/FunctionImport/funcimport.ll?rev=254170&r1=254169&r2=254170&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/FunctionImport/funcimport.ll (original)
> +++ llvm/trunk/test/Transforms/FunctionImport/funcimport.ll Thu Nov 26 13:22:59 2015
> @@ -14,6 +14,7 @@ define i32 @main() #0 {
> entry:
> call void (...) @weakalias()
> call void (...) @analias()
> + call void (...) @linkoncealias()
> %call = call i32 (...) @referencestatics()
> %call1 = call i32 (...) @referenceglobals()
> %call2 = call i32 (...) @referencecommon()
> @@ -27,11 +28,15 @@ entry:
> ; CHECK-DAG: declare extern_weak void @weakalias()
> declare void @weakalias(...) #1
>
> -; Aliases import the aliasee function
> -; CHECK-DAG: @analias = alias void (...), bitcast (void ()* @globalfunc2 to void (...)*)
> -; CHECK-DAG: define available_externally void @globalfunc2()
> +; Cannot create an alias to available_externally
> +; CHECK-DAG: declare void @analias()
> declare void @analias(...) #1
>
> +; Aliases import the aliasee function
> +declare void @linkoncealias(...) #1
> +; CHECK-DAG: define linkonce_odr void @linkoncefunc()
> +; CHECK-DAG: @linkoncealias = alias void (...), bitcast (void ()* @linkoncefunc to void (...)*
> +
> ; INSTLIMDEF-DAG: define available_externally i32 @referencestatics(i32 %i)
> ; INSTLIM5-DAG: declare i32 @referencestatics(...)
> declare i32 @referencestatics(...) #1
>
> Modified: llvm/trunk/test/Verifier/alias.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Verifier/alias.ll?rev=254170&r1=254169&r2=254170&view=diff
> ==============================================================================
> --- llvm/trunk/test/Verifier/alias.ll (original)
> +++ llvm/trunk/test/Verifier/alias.ll Thu Nov 26 13:22:59 2015
> @@ -11,6 +11,12 @@ declare void @f()
> ; CHECK: Alias must point to a definition
> ; CHECK-NEXT: @ga
>
> +define available_externally void @f2() {
> + ret void
> +}
> + at fa2 = alias void(), void()* @f2
> +; CHECK: Alias must point to a definition
> +; CHECK-NEXT: @fa2
>
> @test2_a = alias i32, i32* @test2_b
> @test2_b = alias i32, i32* @test2_a
>
>
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--
Teresa Johnson | Software Engineer | tejohnson at google.com | 408-460-2413
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