tahonermann created this revision.
tahonermann added reviewers: erichkeane, aaron.ballman.
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tahonermann added inline comments.
tahonermann published this revision for review.
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================
Comment at: clang/lib/CodeGen/CodeGenModule.cpp:3771
if (FD->isMultiVersion()) {
- UpdateMultiVersionNames(GD, FD, MangledName);
if (!IsForDefinition)
----------------
This is a drive-by indentation fix.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D122955
Files:
clang/include/clang/Basic/Attr.td
clang/lib/CodeGen/CodeGenModule.cpp
clang/lib/CodeGen/CodeGenModule.h
Index: clang/lib/CodeGen/CodeGenModule.h
===================================================================
--- clang/lib/CodeGen/CodeGenModule.h
+++ clang/lib/CodeGen/CodeGenModule.h
@@ -348,8 +348,9 @@
/// is defined once we get to the end of the of the translation unit.
std::vector<GlobalDecl> Aliases;
- /// List of multiversion functions that have to be emitted. Used to make
sure
- /// we properly emit the iFunc.
+ /// List of multiversion functions to be emitted. This list is processed in
+ /// conjunction with other deferred symbols and is used to ensure that
+ /// multiversion function resolvers and ifuncs are defined and emitted.
std::vector<GlobalDecl> MultiVersionFuncs;
typedef llvm::StringMap<llvm::TrackingVH<llvm::Constant> > ReplacementsTy;
@@ -1466,9 +1467,20 @@
llvm::AttributeList ExtraAttrs = llvm::AttributeList(),
ForDefinition_t IsForDefinition = NotForDefinition);
+ // References to multiversion functions are resolved through an implicitly
+ // defined resolver function. This function is responsible for creating
+ // the resolver symbol for the provided declaration. The value returned
+ // will be for an ifunc (llvm::GlobalIFunc) if the current target supports
+ // that feature and for a regular function (llvm::GlobalValue) otherwise.
llvm::Constant *GetOrCreateMultiVersionResolver(GlobalDecl GD,
llvm::Type *DeclTy,
const FunctionDecl *FD);
+
+ // In scenarios where a function is not known to be a multiversion function
+ // until a later declaration, it is sometimes necessary to change the
+ // previously created mangled name to align with requirements of whatever
+ // multiversion function kind the function is now known to be. This function
+ // is responsible for performing such mangled name updates.
void UpdateMultiVersionNames(GlobalDecl GD, const FunctionDecl *FD,
StringRef &CurName);
@@ -1561,6 +1573,7 @@
// registered by the atexit subroutine using unatexit.
void unregisterGlobalDtorsWithUnAtExit();
+ /// Emit deferred multiversion function resolvers and associated variants.
void emitMultiVersionFunctions();
/// Emit any vtables which we deferred and still have a use for.
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -3768,7 +3768,7 @@
}
if (FD->isMultiVersion()) {
- UpdateMultiVersionNames(GD, FD, MangledName);
+ UpdateMultiVersionNames(GD, FD, MangledName);
if (!IsForDefinition)
return GetOrCreateMultiVersionResolver(GD, Ty, FD);
}
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2723,8 +2723,13 @@
StringRef getFeatureStr(unsigned Index) const {
return *(featuresStrs_begin() + Index);
}
- // 'default' is always moved to the end, so it isn't considered
- // when mangling the index.
+ // Given an index into the 'featuresStrs' sequence, compute a unique
+ // ID to be used with function name mangling for the associated variant.
+ // This mapping is necessary due to a requirement that the mangling ID
+ // used for the "default" variant be the largest mangling ID in the
+ // variant set. Note that, if duplicate variants are present in
+ // 'featuresStrs', that each instance will be assigned its own unique
+ // ID (the mapping is bijective).
unsigned getMangledIndex(unsigned Index) const {
if (getFeatureStr(Index) == "default")
return std::count_if(featuresStrs_begin(), featuresStrs_end(),
@@ -2734,9 +2739,10 @@
[](StringRef S) { return S != "default"; });
}
- // True if this is the first of this version to appear in the config
string.
- // This is used to make sure we don't try to emit this function multiple
- // times.
+ // Given an index into the 'featuresStrs' sequence, determine if the
+ // index corresponds to the first instance of the named variant. This
+ // is used to skip over duplicate variant instances when iterating over
+ // 'featuresStrs'.
bool isFirstOfVersion(unsigned Index) const {
StringRef FeatureStr(getFeatureStr(Index));
return 0 == std::count_if(
Index: clang/lib/CodeGen/CodeGenModule.h
===================================================================
--- clang/lib/CodeGen/CodeGenModule.h
+++ clang/lib/CodeGen/CodeGenModule.h
@@ -348,8 +348,9 @@
/// is defined once we get to the end of the of the translation unit.
std::vector<GlobalDecl> Aliases;
- /// List of multiversion functions that have to be emitted. Used to make sure
- /// we properly emit the iFunc.
+ /// List of multiversion functions to be emitted. This list is processed in
+ /// conjunction with other deferred symbols and is used to ensure that
+ /// multiversion function resolvers and ifuncs are defined and emitted.
std::vector<GlobalDecl> MultiVersionFuncs;
typedef llvm::StringMap<llvm::TrackingVH<llvm::Constant> > ReplacementsTy;
@@ -1466,9 +1467,20 @@
llvm::AttributeList ExtraAttrs = llvm::AttributeList(),
ForDefinition_t IsForDefinition = NotForDefinition);
+ // References to multiversion functions are resolved through an implicitly
+ // defined resolver function. This function is responsible for creating
+ // the resolver symbol for the provided declaration. The value returned
+ // will be for an ifunc (llvm::GlobalIFunc) if the current target supports
+ // that feature and for a regular function (llvm::GlobalValue) otherwise.
llvm::Constant *GetOrCreateMultiVersionResolver(GlobalDecl GD,
llvm::Type *DeclTy,
const FunctionDecl *FD);
+
+ // In scenarios where a function is not known to be a multiversion function
+ // until a later declaration, it is sometimes necessary to change the
+ // previously created mangled name to align with requirements of whatever
+ // multiversion function kind the function is now known to be. This function
+ // is responsible for performing such mangled name updates.
void UpdateMultiVersionNames(GlobalDecl GD, const FunctionDecl *FD,
StringRef &CurName);
@@ -1561,6 +1573,7 @@
// registered by the atexit subroutine using unatexit.
void unregisterGlobalDtorsWithUnAtExit();
+ /// Emit deferred multiversion function resolvers and associated variants.
void emitMultiVersionFunctions();
/// Emit any vtables which we deferred and still have a use for.
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -3768,7 +3768,7 @@
}
if (FD->isMultiVersion()) {
- UpdateMultiVersionNames(GD, FD, MangledName);
+ UpdateMultiVersionNames(GD, FD, MangledName);
if (!IsForDefinition)
return GetOrCreateMultiVersionResolver(GD, Ty, FD);
}
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2723,8 +2723,13 @@
StringRef getFeatureStr(unsigned Index) const {
return *(featuresStrs_begin() + Index);
}
- // 'default' is always moved to the end, so it isn't considered
- // when mangling the index.
+ // Given an index into the 'featuresStrs' sequence, compute a unique
+ // ID to be used with function name mangling for the associated variant.
+ // This mapping is necessary due to a requirement that the mangling ID
+ // used for the "default" variant be the largest mangling ID in the
+ // variant set. Note that, if duplicate variants are present in
+ // 'featuresStrs', that each instance will be assigned its own unique
+ // ID (the mapping is bijective).
unsigned getMangledIndex(unsigned Index) const {
if (getFeatureStr(Index) == "default")
return std::count_if(featuresStrs_begin(), featuresStrs_end(),
@@ -2734,9 +2739,10 @@
[](StringRef S) { return S != "default"; });
}
- // True if this is the first of this version to appear in the config string.
- // This is used to make sure we don't try to emit this function multiple
- // times.
+ // Given an index into the 'featuresStrs' sequence, determine if the
+ // index corresponds to the first instance of the named variant. This
+ // is used to skip over duplicate variant instances when iterating over
+ // 'featuresStrs'.
bool isFirstOfVersion(unsigned Index) const {
StringRef FeatureStr(getFeatureStr(Index));
return 0 == std::count_if(
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