Commit 3bc2d0a6 authored by Tom Stellard's avatar Tom Stellard
Browse files

Merging r329300: 

------------------------------------------------------------------------
r329300 | manojgupta | 2018-04-05 08:29:52 -0700 (Thu, 05 Apr 2018) | 16 lines

Disable -fmerge-all-constants as default.

Summary:
"-fmerge-all-constants" is a non-conforming optimization and should not
be the default. It is also causing miscompiles when building Linux
Kernel (https://lkml.org/lkml/2018/3/20/872).

Fixes PR18538.

Reviewers: rjmccall, rsmith, chandlerc

Reviewed By: rsmith, chandlerc

Subscribers: srhines, cfe-commits

Differential Revision: https://reviews.llvm.org/D45289
------------------------------------------------------------------------

llvm-svn: 333564
parent 374c27a4

clang/include/clang/Driver/Options.td

+3 −2
Original line number Diff line number Diff line
@@ -1100,7 +1100,8 @@ def fthinlto_index_EQ : Joined<["-"], "fthinlto-index=">, 
  HelpText<"Perform ThinLTO importing using provided function summary index">;

def fmacro_backtrace_limit_EQ : Joined<["-"], "fmacro-backtrace-limit=">,

                                Group<f_Group>, Flags<[DriverOption, CoreOption]>;

def fmerge_all_constants : Flag<["-"], "fmerge-all-constants">, Group<f_Group>;

def fmerge_all_constants : Flag<["-"], "fmerge-all-constants">, Group<f_Group>,

  Flags<[CC1Option]>, HelpText<"Allow merging of constants">;

def fmessage_length_EQ : Joined<["-"], "fmessage-length=">, Group<f_Group>;

def fms_extensions : Flag<["-"], "fms-extensions">, Group<f_Group>, Flags<[CC1Option, CoreOption]>,

  HelpText<"Accept some non-standard constructs supported by the Microsoft compiler">;
@@ -1249,7 +1250,7 @@ def fveclib : Joined<["-"], "fveclib=">, Group<f_Group>, Flags<[CC1Option]>, 
def fno_lax_vector_conversions : Flag<["-"], "fno-lax-vector-conversions">, Group<f_Group>,

  HelpText<"Disallow implicit conversions between vectors with a different number of elements or different element types">, Flags<[CC1Option]>;

def fno_merge_all_constants : Flag<["-"], "fno-merge-all-constants">, Group<f_Group>,

    Flags<[CC1Option]>, HelpText<"Disallow merging of constants">;

  HelpText<"Disallow merging of constants">;

def fno_modules : Flag <["-"], "fno-modules">, Group<f_Group>,

  Flags<[DriverOption]>;

def fno_implicit_module_maps : Flag <["-"], "fno-implicit-module-maps">, Group<f_Group>,

clang/lib/AST/ExprConstant.cpp

+0 −3
Original line number Diff line number Diff line
@@ -8543,9 +8543,6 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) { 
            (LHSValue.Base && isZeroSized(RHSValue)))

          return Error(E);

        // Pointers with different bases cannot represent the same object.

        // (Note that clang defaults to -fmerge-all-constants, which can

        // lead to inconsistent results for comparisons involving the address

        // of a constant; this generally doesn't matter in practice.)

        return Success(E->getOpcode() == BO_NE, E);

      }

clang/lib/Driver/ToolChains/Clang.cpp

+3 −3
Original line number Diff line number Diff line
@@ -3288,9 +3288,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA, 


  Args.AddLastArg(CmdArgs, options::OPT_fveclib);



  if (!Args.hasFlag(options::OPT_fmerge_all_constants,

                    options::OPT_fno_merge_all_constants))

    CmdArgs.push_back("-fno-merge-all-constants");

  if (Args.hasFlag(options::OPT_fmerge_all_constants,

                   options::OPT_fno_merge_all_constants, false))

    CmdArgs.push_back("-fmerge-all-constants");



  // LLVM Code Generator Options.

clang/lib/Frontend/CompilerInvocation.cpp

+1 −1
Original line number Diff line number Diff line
@@ -552,7 +552,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK, 
      Args.hasFlag(OPT_ffine_grained_bitfield_accesses,

                   OPT_fno_fine_grained_bitfield_accesses, false);

  Opts.DwarfDebugFlags = Args.getLastArgValue(OPT_dwarf_debug_flags);

  Opts.MergeAllConstants = !Args.hasArg(OPT_fno_merge_all_constants);

  Opts.MergeAllConstants = Args.hasArg(OPT_fmerge_all_constants);

  Opts.NoCommon = Args.hasArg(OPT_fno_common);

  Opts.NoImplicitFloat = Args.hasArg(OPT_no_implicit_float);

  Opts.OptimizeSize = getOptimizationLevelSize(Args);

clang/test/CodeGen/decl.c

+1 −1
Original line number Diff line number Diff line 
// RUN: %clang_cc1 -w -emit-llvm < %s | FileCheck %s

// RUN: %clang_cc1 -w -fmerge-all-constants -emit-llvm < %s | FileCheck %s



// CHECK: @test1.x = internal constant [12 x i32] [i32 1

// CHECK: @test2.x = private unnamed_addr constant [13 x i32] [i32 1,