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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@329300 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index abec5edddf9a3f35af80de3c7467cceb599f621a..c72bb39ec5c777eb785a2dc84189dd3cabe82035 100644 (file)
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -1133,7 +1133,8 @@ 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">;
@@ -1282,7 +1283,7 @@ 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>,

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 6de55f10dc579bf9a0636556d79e1213addc3c94..4725b1b56943bc8f17d35144c1b1812dbfa2b6e9 100644 (file)
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -8596,9 +8596,6 @@ 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);
       }
 

diff --git a/lib/Driver/ToolChains/Clang.cpp b/lib/Driver/ToolChains/Clang.cpp
index a86c5376e4c4641811f47698f933eacbfa72cd21..8e11e872d474b24c61b81eea637facf9a435c07d 100644 (file)
--- a/lib/Driver/ToolChains/Clang.cpp
+++ b/lib/Driver/ToolChains/Clang.cpp
@@ -3361,9 +3361,9 @@ 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.
 

diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 734349eed7ac04fa22646695c3dfe4bc027406a8..45546ac3bc795b31484d78a37913b0c6df003ef3 100644 (file)
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -605,7 +605,7 @@ 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);

diff --git a/test/CodeGen/array-init.c b/test/CodeGen/array-init.c
index fa54994acc3ed204661e839ecb19de293ad0633c..62e87edc29741977982ae91ab988c96e72824046 100644 (file)
--- a/test/CodeGen/array-init.c
+++ b/test/CodeGen/array-init.c
@@ -1,8 +1,11 @@
-// RUN: %clang_cc1 %s -O0 -triple x86_64-unknown-linux-gnu -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 %s -O0 -triple x86_64-unknown-linux-gnu -emit-llvm -o - | FileCheck -check-prefix=CHECK-NO-MERGE-CONSTANTS %s
+// RUN: %clang_cc1 %s -O0 -triple x86_64-unknown-linux-gnu -fmerge-all-constants -emit-llvm -o - | FileCheck -check-prefix=CHECK-MERGE-CONSTANTS %s
 
-// CHECK: @{{.*}}.a1 = internal constant [5 x i32] [i32 0, i32 1, i32 2, i32 0, i32 0]
-// CHECK: @{{.*}}.a2 = internal constant [5 x i32] zeroinitializer
-// CHECK: @{{.*}}.a3 = internal constant [5 x i32] zeroinitializer
+// CHECK-NO-MERGE-CONSTANTS: @{{.*}}.a1 = private unnamed_addr constant [5 x i32] [i32 0, i32 1, i32 2, i32 0, i32 0]
+
+// CHECK-MERGE-CONSTANTS: @{{.*}}.a1 = internal constant [5 x i32] [i32 0, i32 1, i32 2, i32 0, i32 0]
+// CHECK-MERGE-CONSTANTS: @{{.*}}.a2 = internal constant [5 x i32] zeroinitializer
+// CHECK-MERGE-CONSTANTS: @{{.*}}.a3 = internal constant [5 x i32] zeroinitializer
 
 void testConstArrayInits(void)
 {

diff --git a/test/CodeGen/decl.c b/test/CodeGen/decl.c
index ffee1e3cef137d7dc9fe96dd5699535ad6b11b24..d62629c7fb5cf12d3010754d5b3246db36c08eb5 100644 (file)
--- a/test/CodeGen/decl.c
+++ b/test/CodeGen/decl.c
@@ -1,4 +1,4 @@
-// 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,

diff --git a/test/CodeGenCXX/const-init-cxx11.cpp b/test/CodeGenCXX/const-init-cxx11.cpp
index c4962bc08ad698443d158727754fa7270980ff2b..801d7b1e19cc4bae8dcd5ad58161b7eaadb11d80 100644 (file)
--- a/test/CodeGenCXX/const-init-cxx11.cpp
+++ b/test/CodeGenCXX/const-init-cxx11.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -w -triple x86_64-elf-gnu -emit-llvm -o - %s -std=c++11 | FileCheck %s
+// RUN: %clang_cc1 -w -fmerge-all-constants -triple x86_64-elf-gnu -emit-llvm -o - %s -std=c++11 | FileCheck %s
 
 // FIXME: The padding in all these objects should be zero-initialized.
 namespace StructUnion {

diff --git a/test/CodeGenCXX/cxx0x-initializer-references.cpp b/test/CodeGenCXX/cxx0x-initializer-references.cpp
index 318c8ea0d77039fdffcd230e852fdb87a5c7c80e..595d27ca2e83400bd72ba512c27b0ae4ec953263 100644 (file)
--- a/test/CodeGenCXX/cxx0x-initializer-references.cpp
+++ b/test/CodeGenCXX/cxx0x-initializer-references.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=c++11 -S -triple armv7-none-eabi -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -S -triple armv7-none-eabi -fmerge-all-constants -emit-llvm -o - %s | FileCheck %s
 
 namespace reference {
   struct A {

diff --git a/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp b/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp
index e1c18169a8a7034697779fbc26ff877c5de36035..3299763997e5d004eb1551ad97ddfe318ca8b6d2 100644 (file)
--- a/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp
+++ b/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp
@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 -std=c++11 -triple x86_64-none-linux-gnu -emit-llvm -o - %s | FileCheck -check-prefixes=X86,CHECK %s
-// RUN: %clang_cc1 -std=c++11 -triple amdgcn-amd-amdhsa -DNO_TLS -emit-llvm -o - %s | FileCheck -check-prefixes=AMDGCN,CHECK %s
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-none-linux-gnu -fmerge-all-constants -emit-llvm -o - %s | FileCheck -check-prefixes=X86,CHECK %s
+// RUN: %clang_cc1 -std=c++11 -triple amdgcn-amd-amdhsa -DNO_TLS -fmerge-all-constants -emit-llvm -o - %s | FileCheck -check-prefixes=AMDGCN,CHECK %s
 
 namespace std {
   typedef decltype(sizeof(int)) size_t;

diff --git a/test/CodeGenObjCXX/arc-cxx11-init-list.mm b/test/CodeGenObjCXX/arc-cxx11-init-list.mm
index c3723c619ab00809d1f774537790b6e005758638..af607654e159086f2312e340a8f67b4d0f11339b 100644 (file)
--- a/test/CodeGenObjCXX/arc-cxx11-init-list.mm
+++ b/test/CodeGenObjCXX/arc-cxx11-init-list.mm
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple armv7-ios5.0 -std=c++11 -fobjc-arc -Os -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple armv7-ios5.0 -std=c++11 -fmerge-all-constants -fobjc-arc -Os -emit-llvm -o - %s | FileCheck %s
 
 // CHECK: @[[STR0:.*]] = private unnamed_addr constant [5 x i8] c"str0\00", section "__TEXT,__cstring,cstring_literals"
 // CHECK: @[[UNNAMED_CFSTRING0:.*]] = private global %struct.__NSConstantString_tag { i32* getelementptr inbounds ([0 x i32], [0 x i32]* @__CFConstantStringClassReference, i32 0, i32 0), i32 1992, i8* getelementptr inbounds ([5 x i8], [5 x i8]* @[[STR0]], i32 0, i32 0), i32 4 }, section "__DATA,__cfstring"

diff --git a/test/Driver/clang_f_opts.c b/test/Driver/clang_f_opts.c
index 9c90f0e58f42327fd6625890f59022272ebcbb21..2b2a7e7b98fefda9475a3faccb71d87ce1317fd5 100644 (file)
--- a/test/Driver/clang_f_opts.c
+++ b/test/Driver/clang_f_opts.c
@@ -276,6 +276,7 @@
 // RUN:     -fno-inline-small-functions -finline-small-functions              \
 // RUN:     -fno-fat-lto-objects -ffat-lto-objects                            \
 // RUN:     -fno-merge-constants -fmerge-constants                            \
+// RUN:     -fno-merge-all-constants -fmerge-all-constants                    \
 // RUN:     -fno-caller-saves -fcaller-saves                                  \
 // RUN:     -fno-reorder-blocks -freorder-blocks                              \
 // RUN:     -fno-schedule-insns2 -fschedule-insns2                            \
@@ -522,3 +523,10 @@
 // RUN: %clang -### -S -fno-discard-value-names %s 2>&1 | FileCheck -check-prefix=CHECK-NO-DISCARD-NAMES %s
 // CHECK-DISCARD-NAMES: "-discard-value-names"
 // CHECK-NO-DISCARD-NAMES-NOT: "-discard-value-names"
+//
+// RUN: %clang -### -S -fmerge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-MERGE-ALL-CONSTANTS %s
+// RUN: %clang -### -S -fno-merge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MERGE-ALL-CONSTANTS %s
+// RUN: %clang -### -S -fmerge-all-constants -fno-merge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MERGE-ALL-CONSTANTS %s
+// RUN: %clang -### -S -fno-merge-all-constants -fmerge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-MERGE-ALL-CONSTANTS %s
+// CHECK-NO-MERGE-ALL-CONSTANTS-NOT: "-fmerge-all-constants"
+// CHECK-MERGE-ALL-CONSTANTS: "-fmerge-all-constants"