lebedev.ri updated this revision to Diff 335894.
lebedev.ri added a comment.
Herald added subscribers: jansvoboda11, dexonsmith, dang.
Add an option to toggle this optimization.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D99791/new/
https://reviews.llvm.org/D99791
Files:
clang/docs/ClangCommandLineReference.rst
clang/docs/ReleaseNotes.rst
clang/docs/UsersManual.rst
clang/include/clang/Basic/CodeGenOptions.def
clang/include/clang/Driver/Options.td
clang/lib/CodeGen/CGCall.cpp
clang/lib/Driver/ToolChains/Clang.cpp
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -4872,6 +4872,10 @@
options::OPT_fno_force_emit_vtables,
false))
CmdArgs.push_back("-fforce-emit-vtables");
+ if (Args.hasFlag(options::OPT_fstrict_pointer_alignment,
+ options::OPT_fno_strict_pointer_alignment,
+ !RawTriple.isOSDarwin()))
+ CmdArgs.push_back("-fstrict-pointer-alignment");
if (!Args.hasFlag(options::OPT_foptimize_sibling_calls,
options::OPT_fno_optimize_sibling_calls))
CmdArgs.push_back("-mdisable-tail-calls");
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -2446,6 +2446,17 @@
}
}
+ if (getCodeGenOpts().StrictPointerAlignment) {
+ if (const auto *PtrTy = ParamType->getAs<PointerType>()) {
+ QualType PTy = PtrTy->getPointeeType();
+ if (PTy->isObjectType()) {
+ llvm::Align Alignment =
+ getNaturalPointeeTypeAlignment(ParamType).getAsAlign();
+ Attrs.addAlignmentAttr(Alignment);
+ }
+ }
+ }
+
switch (FI.getExtParameterInfo(ArgNo).getABI()) {
case ParameterABI::Ordinary:
break;
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -2446,6 +2446,11 @@
PosFlag<SetTrue, [CC1Option], "Enable optimizations based on the strict rules for"
" overwriting polymorphic C++ objects">,
NegFlag<SetFalse>>;
+defm strict_pointer_alignment : BoolFOption<"strict-pointer-alignment",
+ CodeGenOpts<"StrictPointerAlignment">, DefaultFalse,
+ NegFlag<SetFalse, [CC1Option], "Disable">,
+ PosFlag<SetTrue, [CC1Option], "Enable">,
+ BothFlags<[], " optimizations based on the strict rules for pointer alignmen">>;
def fstrict_overflow : Flag<["-"], "fstrict-overflow">, Group<f_Group>;
def fsyntax_only : Flag<["-"], "fsyntax-only">,
Flags<[NoXarchOption,CoreOption,CC1Option,FC1Option]>, Group<Action_Group>;
Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -261,6 +261,7 @@
CODEGENOPT(FineGrainedBitfieldAccesses, 1, 0) ///< Enable fine-grained bitfield accesses.
CODEGENOPT(StrictEnums , 1, 0) ///< Optimize based on strict enum definition.
CODEGENOPT(StrictVTablePointers, 1, 0) ///< Optimize based on the strict vtable pointers
+CODEGENOPT(StrictPointerAlignment, 1, 1) ///< Optimize based on the strict pointer alignment rules
CODEGENOPT(TimePasses , 1, 0) ///< Set when -ftime-report or -ftime-report= is enabled.
CODEGENOPT(TimePassesPerRun , 1, 0) ///< Set when -ftime-report=per-pass-run is enabled.
CODEGENOPT(TimeTrace , 1, 0) ///< Set when -ftime-trace is enabled.
Index: clang/docs/UsersManual.rst
===================================================================
--- clang/docs/UsersManual.rst
+++ clang/docs/UsersManual.rst
@@ -1669,6 +1669,12 @@
modules where it isn't necessary. It causes more inline virtual functions
to be emitted.
+.. option:: -fstrict-pointer-alignment
+
+ Enable optimizations based on the strict rules for pointer alignment.
+ This currently only affects function pointer arguments, and only controls
+ UBSan behaviour, no optimizations are currently performed based on it.
+
.. option:: -fno-assume-sane-operator-new
Don't assume that the C++'s new operator is sane.
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -54,6 +54,10 @@
to allow codebases to be cleaned up in preparation for this optimization,
to avoid miscompiles.
+- Clang now assumes that all function pointer arguments are properly aligned,
+ and optimizes on that. A new ``-fstrict-pointer-alignment`` flag was
+ introduces (default on), which guards these new optimizations.
+
Improvements to Clang's diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Index: clang/docs/ClangCommandLineReference.rst
===================================================================
--- clang/docs/ClangCommandLineReference.rst
+++ clang/docs/ClangCommandLineReference.rst
@@ -2222,6 +2222,10 @@
Enable optimizations based on the strict rules for overwriting polymorphic C++ objects
+.. option:: -fstrict-pointer-alignment, -fno-strict-pointer-alignment
+
+Enable optimizations based on the strict rules for pointer alignment
+
.. option:: -fstruct-path-tbaa, -fno-struct-path-tbaa
.. option:: -fsymbol-partition=<arg>
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
