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Bryce-MW retitled this revision from "[CGCall] Annotate op new with
inaccessiblememonly if AssumeSaneOperatorNew is on" to "[CGCall] Annotate
operator new with inaccessiblememonly if AssumeSaneOperatorNew is on".
Bryce-MW edited the summary of this revision.
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- Add change to docs
Basic Alias Analysis in LLVM currently has a special case for allocation
functions (including operator new) that essentially assumes that they are
inaccessiblememonly. Operator new is not currently annotated with
inaccessiblememonly because that is not technically correct (especially
considering global replacement functions). This patch allows that case to be
removed (D117180 <https://reviews.llvm.org/D117180>) allowing operator new to
be correct when needed without causing the significant regression that we found
when removing the special case).
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D117600
Files:
clang/include/clang/Driver/Options.td
clang/lib/CodeGen/CGCall.cpp
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -2062,11 +2062,14 @@
AddAttributesFromFunctionProtoType(
getContext(), FuncAttrs, Fn->getType()->getAs<FunctionProtoType>());
if (AttrOnCallSite && Fn->isReplaceableGlobalAllocationFunction()) {
- // A sane operator new returns a non-aliasing pointer.
+ // A sane operator new returns a non-aliasing pointer and is
+ // inaccessiblememonly
auto Kind = Fn->getDeclName().getCXXOverloadedOperator();
if (getCodeGenOpts().AssumeSaneOperatorNew &&
- (Kind == OO_New || Kind == OO_Array_New))
+ (Kind == OO_New || Kind == OO_Array_New)) {
RetAttrs.addAttribute(llvm::Attribute::NoAlias);
+ FuncAttrs.addAttribute("inaccessiblememonly");
+ }
}
const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Fn);
const bool IsVirtualCall = MD && MD->isVirtual();
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -2256,7 +2256,7 @@
def fno_asm : Flag<["-"], "fno-asm">, Group<f_Group>;
def fno_asynchronous_unwind_tables : Flag<["-"],
"fno-asynchronous-unwind-tables">, Group<f_Group>;
def fno_assume_sane_operator_new : Flag<["-"],
"fno-assume-sane-operator-new">, Group<f_Group>,
- HelpText<"Don't assume that C++'s global operator new can't alias any
pointer">,
+ HelpText<"Don't assume that C++'s global operator new can't alias any
pointer or access accessible memory">,
Flags<[CC1Option]>,
MarshallingInfoNegativeFlag<CodeGenOpts<"AssumeSaneOperatorNew">>;
def fno_builtin : Flag<["-"], "fno-builtin">, Group<f_Group>,
Flags<[CC1Option, CoreOption]>,
HelpText<"Disable implicit builtin knowledge of functions">;
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -2062,11 +2062,14 @@
AddAttributesFromFunctionProtoType(
getContext(), FuncAttrs, Fn->getType()->getAs<FunctionProtoType>());
if (AttrOnCallSite && Fn->isReplaceableGlobalAllocationFunction()) {
- // A sane operator new returns a non-aliasing pointer.
+ // A sane operator new returns a non-aliasing pointer and is
+ // inaccessiblememonly
auto Kind = Fn->getDeclName().getCXXOverloadedOperator();
if (getCodeGenOpts().AssumeSaneOperatorNew &&
- (Kind == OO_New || Kind == OO_Array_New))
+ (Kind == OO_New || Kind == OO_Array_New)) {
RetAttrs.addAttribute(llvm::Attribute::NoAlias);
+ FuncAttrs.addAttribute("inaccessiblememonly");
+ }
}
const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Fn);
const bool IsVirtualCall = MD && MD->isVirtual();
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -2256,7 +2256,7 @@
def fno_asm : Flag<["-"], "fno-asm">, Group<f_Group>;
def fno_asynchronous_unwind_tables : Flag<["-"], "fno-asynchronous-unwind-tables">, Group<f_Group>;
def fno_assume_sane_operator_new : Flag<["-"], "fno-assume-sane-operator-new">, Group<f_Group>,
- HelpText<"Don't assume that C++'s global operator new can't alias any pointer">,
+ HelpText<"Don't assume that C++'s global operator new can't alias any pointer or access accessible memory">,
Flags<[CC1Option]>, MarshallingInfoNegativeFlag<CodeGenOpts<"AssumeSaneOperatorNew">>;
def fno_builtin : Flag<["-"], "fno-builtin">, Group<f_Group>, Flags<[CC1Option, CoreOption]>,
HelpText<"Disable implicit builtin knowledge of functions">;
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