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[ElimAvailExtern] Add an option to allow to convert global variables in a specified address space to local #144287

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[ElimAvailExtern] Add an option to allow to convert global variables in a specified address space to local #144287

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36 changes: 32 additions & 4 deletions llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -35,8 +35,15 @@ static cl::opt<bool> ConvertToLocal(
cl::desc("Convert available_externally into locals, renaming them "
"to avoid link-time clashes."));

static cl::opt<unsigned> ConvertGlobalVariableInAddrSpace(
"avail-extern-gv-in-addrspace-to-local", cl::Hidden,
cl::desc(
"Convert available_externally global variables into locals if they are "
"in specificed addrspace, renaming them to avoid link-time clashes."));

STATISTIC(NumRemovals, "Number of functions removed");
STATISTIC(NumConversions, "Number of functions converted");
STATISTIC(NumFunctionsConverted, "Number of functions converted");
STATISTIC(NumGlobalVariablesConverted, "Number of global variables converted");
STATISTIC(NumVariables, "Number of global variables removed");

void deleteFunction(Function &F) {
Expand All @@ -45,6 +52,10 @@ void deleteFunction(Function &F) {
++NumRemovals;
}

static std::string getNewName(Module &M, const GlobalValue &GV) {
return GV.getName().str() + ".__uniq" + getUniqueModuleId(&M);
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nit: I meant also pull into the refactoring the setting of the name and the setting of the linkage type - basically reusing convertToLocalCopy

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I tried that route but not sure if that would be better. The new name is used at L85 as well. If we are gonna have a function that does both rename and set linkage, it also needs to return the new name for L85, which I find the semantics of it weird.

}

/// Create a copy of the thinlto import, mark it local, and redirect direct
/// calls to the copy. Only direct calls are replaced, so that e.g. indirect
/// call function pointer tests would use the global identity of the function.
Expand All @@ -68,7 +79,7 @@ static void convertToLocalCopy(Module &M, Function &F) {
// functions with the same name, but that just creates more trouble than
// necessary e.g. distinguishing profiles or debugging. Instead, we append the
// module identifier.
auto NewName = OrigName + ".__uniq" + getUniqueModuleId(&M);
std::string NewName = getNewName(M, F);
F.setName(NewName);
if (auto *SP = F.getSubprogram())
SP->replaceLinkageName(MDString::get(F.getParent()->getContext(), NewName));
Expand All @@ -85,16 +96,33 @@ static void convertToLocalCopy(Module &M, Function &F) {
F.getAddressSpace(), OrigName, F.getParent());
F.replaceUsesWithIf(Decl,
[&](Use &U) { return !isa<CallBase>(U.getUser()); });
++NumConversions;
++NumFunctionsConverted;
}

/// Similar to the function above, this is to convert an externally available
/// global variable to local.
static void convertToLocalCopy(Module &M, GlobalVariable &GV) {
assert(GV.hasAvailableExternallyLinkage());
GV.setName(getNewName(M, GV));
GV.setLinkage(GlobalValue::InternalLinkage);
++NumGlobalVariablesConverted;
}

static bool eliminateAvailableExternally(Module &M, bool Convert) {
bool Changed = false;

// Drop initializers of available externally global variables.
// If a global variable is available externally and in the specified address
// space, convert it to local linkage; otherwise, drop its initializer.
for (GlobalVariable &GV : M.globals()) {
if (!GV.hasAvailableExternallyLinkage())
continue;
if (ConvertGlobalVariableInAddrSpace.getNumOccurrences() &&
GV.getAddressSpace() == ConvertGlobalVariableInAddrSpace &&
!GV.use_empty()) {
convertToLocalCopy(M, GV);
Changed = true;
continue;
}
if (GV.hasInitializer()) {
Constant *Init = GV.getInitializer();
GV.setInitializer(nullptr);
Expand Down
21 changes: 21 additions & 0 deletions llvm/test/Transforms/EliminateAvailableExternally/convert-global-variables-to-local.ll
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@@ -0,0 +1,21 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
; RUN: opt -S -passes=elim-avail-extern -avail-extern-gv-in-addrspace-to-local=3 %s -o - | FileCheck %s

@shared = internal addrspace(3) global i32 undef, align 4
@shared.imported = available_externally hidden unnamed_addr addrspace(3) global i32 undef, align 4

;.
; CHECK: @shared = internal addrspace(3) global i32 undef, align 4
; CHECK: @shared.imported.__uniq.[[UUID:.*]] = internal unnamed_addr addrspace(3) global i32 undef, align 4
;.
define void @foo(i32 %v) {
; CHECK-LABEL: define void @foo(
; CHECK-SAME: i32 [[V:%.*]]) {
; CHECK-NEXT: store i32 [[V]], ptr addrspace(3) @shared, align 4
; CHECK-NEXT: store i32 [[V]], ptr addrspace(3) @shared.imported.__uniq.[[UUID]], align 4
; CHECK-NEXT: ret void
;
store i32 %v, ptr addrspace(3) @shared, align 4
store i32 %v, ptr addrspace(3) @shared.imported, align 4
ret void
}
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