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[don't merge] IRGen should emit code for unused private functions at -Onone -g #2914

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[don't merge] IRGen should emit code for unused private functions at -Onone -g #2914

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23 changes: 22 additions & 1 deletion lib/IRGen/GenDecl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -802,8 +802,19 @@ void IRGenerator::emitGlobalTopLevel() {
bool isWholeModule = PrimaryIGM->getSILModule().isWholeModule();
for (SILFunction &f : PrimaryIGM->getSILModule()) {
// Only eagerly emit functions that are externally visible.
if (!isPossiblyUsedExternally(f.getLinkage(), isWholeModule))
if (!isPossiblyUsedExternally(f.getLinkage(), isWholeModule)) {
// This function is not externally visible.
// It could be still useful to emit it for debug purposes if it is
// a debug build with disabled optimizations.
// Do not emit this function if it is coming from a binary SIL file
// or if debug info is not supposed to be emitted or if it is a JIT mode.
if (!PrimaryIGM->IRGen.Opts.Optimize && !PrimaryIGM->IRGen.Opts.UseJIT &&
f.hasLocation() && !f.getLocation().isSILFile() &&
PrimaryIGM->DebugInfo) {
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In all of LLVM it is considered a bug if the debug options affect codegen. IMHO, we should also try to live by this rule in Swift. Practically, there are few reasons to build at -Onone without debug information anyway, so I think we don't loose much by just deciding based on IRGen.Opts.Optimize.

addLazyFunction(&f);
}
continue;
}

CurrentIGMPtr IGM = getGenModule(&f);
IGM->emitSILFunction(&f);
Expand Down Expand Up @@ -1660,6 +1671,16 @@ llvm::Function *IRGenModule::getAddrOfSILFunction(SILFunction *f,
llvm::AttributeSet::FunctionIndex, llvm::Attribute::ReadOnly);
}
fn = link.createFunction(*this, fnType, cc, attrs, insertBefore);
if (forDefinition && !link.isUsed()) {
if (IRGen.isLazyFunction(f) &&
f->hasLocation() && !f->getLocation().isSILFile() &&
link.getName() != SWIFT_ENTRY_POINT_FUNCTION) {
// This is a user-defined function and it is an -Onone
// compilation. Mark it as used so that LLVM backend
// does not remove it.
addUsedGlobal(fn);
}
}

// If we have an order number for this function, set it up as appropriate.
if (hasOrderNumber) {
Expand Down
5 changes: 5 additions & 0 deletions lib/IRGen/IRGenModule.h
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Original file line number Diff line number Diff line change
Expand Up @@ -281,6 +281,11 @@ class IRGenerator {
}
}


bool isLazyFunction(SILFunction *f) const {
return LazilyEmittedFunctions.count(f) != 0;
}

void addLazyTypeMetadata(CanType type) {
// Add it to the queue if it hasn't already been put there.
if (LazilyEmittedTypeMetadata.insert(type).second)
Expand Down
24 changes: 24 additions & 0 deletions test/IRGen/unused.swift
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@@ -0,0 +1,24 @@
// RUN: %target-swift-frontend -primary-file %s -emit-ir > %t
// RUN: FileCheck %s --check-prefix=CHECK-ONONE-NODEBUG --check-prefix=CHECK < %t
// RUN: %target-swift-frontend -primary-file %s -emit-ir -g > %t.Onone-debug
// RUN: FileCheck %s --check-prefix=CHECK-ONONE-DEBUG --check-prefix=CHECK < %t.Onone-debug

// Check that unused user-defined functions are preserved at -Onone when -g is used.

// Check that both user functions are marked as used.when using -Onone -g
// CHECK-ONONE-DEBUG: llvm.used{{.*}}_TF6unused7publicFFT_T_{{.*}}_TF6unusedP33_E4A5FE4B57779A0FC903FD67CDBCAAFB8privateFFT_T_{{.*}}

// Check that private function is not marked as used when -g is not used.
// CHECK-ONONE-NODEBUG-NOT: llvm.used{{.*}}_TF6unusedP33_E4A5FE4B57779A0FC903FD67CDBCAAFB8privateFFT_T_{{.*}}

// CHECK-ONONE-DEBUG-LABEL: define{{.*}}void @_TF6unusedP33_E4A5FE4B57779A0FC903FD67CDBCAAFB8privateFFT_T_
// CHECK-ONONE-NODEBUG-NOT: @_TF6unusedP33_E4A5FE4B57779A0FC903FD67CDBCAAFB8privateFFT_T_
private func privateF() {
print(1)
}

// CHECK-LABEL: define{{.*}}void @_TF6unused7publicFFT_T_()
public func publicF() {
print(2)
}