[clang] Change CodeGenOptions::RelaxELFRelocations/assembler defaults to match MC default

MC default was flipped in 2016.
CMake ENABLE_X86_RELAX_RELOCATIONS defaults to on in 2020 (c41a18c).
It makes sense for the CodeGenOptions::RelaxELFRelocations to match, so
that most -cc1/-cc1as command lines won't have this option.

This also fixes a minor issue: -fno-plt -S will now use GOT for
__tls_get_addr calls, matching -fno-plt -c.

Author: MaskRay

clang/include/clang/Basic/CodeGenOptions.def

@@ -30,7 +30,7 @@ CODEGENOPT(Name, Bits, Default)
 CODEGENOPT(DisableIntegratedAS, 1, 0) ///< -no-integrated-as
 ENUM_CODEGENOPT(CompressDebugSections, llvm::DebugCompressionType, 2,
                 llvm::DebugCompressionType::None)
-CODEGENOPT(RelaxELFRelocations, 1, 0) ///< -Wa,--mrelax-relocations
+CODEGENOPT(RelaxELFRelocations, 1, 1) ///< -Wa,-mrelax-relocations={yes,no}
 CODEGENOPT(AsmVerbose        , 1, 0) ///< -dA, -fverbose-asm.
 CODEGENOPT(Dwarf64           , 1, 0) ///< -gdwarf64.
 CODEGENOPT(Dwarf32           , 1, 1) ///< -gdwarf32.

clang/include/clang/Driver/Options.td

@@ -5384,9 +5384,9 @@ def massembler_no_warn : Flag<["-"], "massembler-no-warn">,
 def massembler_fatal_warnings : Flag<["-"], "massembler-fatal-warnings">,
   HelpText<"Make assembler warnings fatal">,
   MarshallingInfoFlag<CodeGenOpts<"FatalWarnings">>;
-def mrelax_relocations : Flag<["--"], "mrelax-relocations">,
-    HelpText<"Use relaxable elf relocations">,
-    MarshallingInfoFlag<CodeGenOpts<"RelaxELFRelocations">>;
+def mrelax_relocations_no : Flag<["-"], "mrelax-relocations=no">,
+    HelpText<"Disable x86 relax relocations">,
+    MarshallingInfoNegativeFlag<CodeGenOpts<"RelaxELFRelocations">>;
 def msave_temp_labels : Flag<["-"], "msave-temp-labels">,
   HelpText<"Save temporary labels in the symbol table. "
            "Note this may change .s semantics and shouldn't generally be used "

clang/lib/Driver/ToolChains/Clang.cpp

@@ -2641,8 +2641,8 @@ static void CollectArgsForIntegratedAssembler(Compilation &C,
   }
   if (ImplicitIt.size())
     AddARMImplicitITArgs(Args, CmdArgs, ImplicitIt);
-  if (UseRelaxRelocations)
-    CmdArgs.push_back("--mrelax-relocations");
+  if (!UseRelaxRelocations)
+    CmdArgs.push_back("-mrelax-relocations=no");
   if (UseNoExecStack)
     CmdArgs.push_back("-mnoexecstack");
   if (MipsTargetFeature != nullptr) {

clang/test/CodeGen/relax.c

@@ -1,5 +1,5 @@
 // REQUIRES: x86-registered-target
-// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -emit-obj --mrelax-relocations %s -mrelocation-model pic -o %t
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -emit-obj %s -mrelocation-model pic -o %t
 // RUN: llvm-readobj -r %t | FileCheck  %s
 
 // CHECK: R_X86_64_REX_GOTPCRELX foo

clang/test/Driver/fuchsia.c

@@ -26,7 +26,6 @@
 // CHECK-X86_64: "-triple" "x86_64-unknown-fuchsia"
 // CHECK-AARCH64: "-triple" "aarch64-unknown-fuchsia"
 // CHECK-RISCV64: "-triple" "riscv64-unknown-fuchsia"
-// CHECK: "--mrelax-relocations"
 // CHECK: "-funwind-tables=2"
 // CHECK: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // CHECK: "-isysroot" "[[SYSROOT:[^"]+]]"

clang/test/Driver/ps4-ps5-relax-relocations.c

@@ -24,6 +24,6 @@
 // RUN: %clang -### -x assembler -target x86_64-sie-ps5 -Wa,-mrelax-relocations=no %s -o - 2>&1 | \
 // RUN:   FileCheck -check-prefix=UNSET %s
 
-// CHECK: "--mrelax-relocations"
+// CHECK-NOT: "-mrelax-relocations
 
-// UNSET-NOT: "--mrelax-relocations"
+// UNSET: "-mrelax-relocations=no"

clang/test/Driver/relax.c

@@ -1,4 +1,4 @@
-// RUN: %clang -### -c -integrated-as -Wa,--mrelax-relocations=yes %s 2>&1 | FileCheck  %s
+// RUN: %clang -### -c -integrated-as -Wa,--mrelax-relocations=no %s 2>&1 | FileCheck  %s
 
 // CHECK: "-cc1"
-// CHECK: "--mrelax-relocations"
+// CHECK: "-mrelax-relocations=no"

clang/test/Driver/relax.s

@@ -1,10 +1,10 @@
 // REQUIRES: x86-registered-target
-// RUN: %clang -### -c -integrated-as -Wa,--mrelax-relocations=yes %s 2>&1 | FileCheck  %s
+// RUN: %clang -### -c -integrated-as -Wa,--mrelax-relocations=no %s 2>&1 | FileCheck %s
 
 // CHECK: "-cc1as"
-// CHECK: "--mrelax-relocations"
+// CHECK: "-mrelax-relocations=no"
 
-// RUN: %clang -cc1as -triple x86_64-pc-linux --mrelax-relocations %s -o %t  -filetype obj
+// RUN: %clang -cc1as -triple x86_64-pc-linux %s -o %t -filetype obj
 // RUN: llvm-readobj -r %t | FileCheck --check-prefix=REL %s
 
 // REL: R_X86_64_REX_GOTPCRELX foo

clang/tools/driver/cc1as_main.cpp

@@ -259,7 +259,7 @@ bool AssemblerInvocation::CreateFromArgs(AssemblerInvocation &Opts,
             .Default(llvm::DebugCompressionType::None);
   }
 
-  Opts.RelaxELFRelocations = Args.hasArg(OPT_mrelax_relocations);
+  Opts.RelaxELFRelocations = !Args.hasArg(OPT_mrelax_relocations_no);
   if (auto *DwarfFormatArg = Args.getLastArg(OPT_gdwarf64, OPT_gdwarf32))
     Opts.Dwarf64 = DwarfFormatArg->getOption().matches(OPT_gdwarf64);
   Opts.DwarfVersion = getLastArgIntValue(Args, OPT_dwarf_version_EQ, 2, Diags);