Rewrite ARM execute only support to avoid the use of a command line flag and unqualified ARMSubtarget lookup.

Paired with a clang commit to use the new behavior.

llvm-svn: 306927

4 files changed, 21 insertions, 29 deletions

diff --git a/llvm/lib/Target/ARM/ARM.td b/llvm/lib/Target/ARM/ARM.td
index c52a1d7611d..c40b4450a5b 100644
--- a/llvm/lib/Target/ARM/ARM.td
+++ b/llvm/lib/Target/ARM/ARM.td
@@ -269,6 +269,10 @@ def FeatureLongCalls : SubtargetFeature<"long-calls", "GenLongCalls", "true",
                                         "Generate calls via indirect call "
                                         "instructions">;
 
+def FeatureExecuteOnly
+    : SubtargetFeature<"execute-only", "GenExecuteOnly", "true",
+                       "Enable the generation of execute only code.">;
+
 def FeatureReserveR9 : SubtargetFeature<"reserve-r9", "ReserveR9", "true",
                                         "Reserve R9, making it unavailable as "
                                         "GPR">;
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.cpp b/llvm/lib/Target/ARM/ARMSubtarget.cpp
index dd38f8a82e2..e7e1a3d285a 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ b/llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -92,11 +92,6 @@ ARMSubtarget &ARMSubtarget::initializeSubtargetDependencies(StringRef CPU,
   return *this;
 }
 
-/// EnableExecuteOnly - Enables the generation of execute-only code on supported
-/// targets
-static cl::opt<bool>
-EnableExecuteOnly("arm-execute-only");
-
 ARMFrameLowering *ARMSubtarget::initializeFrameLowering(StringRef CPU,
                                                         StringRef FS) {
   ARMSubtarget &STI = initializeSubtargetDependencies(CPU, FS);
@@ -139,9 +134,8 @@ ARMSubtarget::ARMSubtarget(const Triple &TT, const std::string &CPU,
                            const std::string &FS,
                            const ARMBaseTargetMachine &TM, bool IsLittle)
     : ARMGenSubtargetInfo(TT, CPU, FS), UseMulOps(UseFusedMulOps),
-      GenExecuteOnly(EnableExecuteOnly), CPUString(CPU), IsLittle(IsLittle),
-      TargetTriple(TT), Options(TM.Options), TM(TM),
-      FrameLowering(initializeFrameLowering(CPU, FS)),
+      CPUString(CPU), IsLittle(IsLittle), TargetTriple(TT), Options(TM.Options),
+      TM(TM), FrameLowering(initializeFrameLowering(CPU, FS)),
       // At this point initializeSubtargetDependencies has been called so
       // we can query directly.
       InstrInfo(isThumb1Only()
diff --git a/llvm/lib/Target/ARM/ARMTargetObjectFile.cpp b/llvm/lib/Target/ARM/ARMTargetObjectFile.cpp
index a5b27abeb27..88bab64ffaf 100644
--- a/llvm/lib/Target/ARM/ARMTargetObjectFile.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetObjectFile.cpp
@@ -32,7 +32,7 @@ void ARMElfTargetObjectFile::Initialize(MCContext &Ctx,
                                         const TargetMachine &TM) {
   const ARMBaseTargetMachine &ARM_TM = static_cast<const ARMBaseTargetMachine &>(TM);
   bool isAAPCS_ABI = ARM_TM.TargetABI == ARMBaseTargetMachine::ARMABI::ARM_ABI_AAPCS;
-  genExecuteOnly = ARM_TM.getSubtargetImpl()->genExecuteOnly();
+  //  genExecuteOnly = ARM_TM.getSubtargetImpl()->genExecuteOnly();
 
   TargetLoweringObjectFileELF::Initialize(Ctx, TM);
   InitializeELF(isAAPCS_ABI);
@@ -43,16 +43,6 @@ void ARMElfTargetObjectFile::Initialize(MCContext &Ctx,
 
   AttributesSection =
       getContext().getELFSection(".ARM.attributes", ELF::SHT_ARM_ATTRIBUTES, 0);
-
-  // Make code section unreadable when in execute-only mode
-  if (genExecuteOnly) {
-    unsigned  Type = ELF::SHT_PROGBITS;
-    unsigned Flags = ELF::SHF_EXECINSTR | ELF::SHF_ALLOC | ELF::SHF_ARM_PURECODE;
-    // Since we cannot modify flags for an existing section, we create a new
-    // section with the right flags, and use 0 as the unique ID for
-    // execute-only text
-    TextSection = Ctx.getELFSection(".text", Type, Flags, 0, "", 0U);
-  }
 }
 
 const MCExpr *ARMElfTargetObjectFile::getTTypeGlobalReference(
@@ -74,21 +64,27 @@ getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
                                  getContext());
 }
 
-MCSection *
-ARMElfTargetObjectFile::getExplicitSectionGlobal(const GlobalObject *GO,
-                                                 SectionKind SK, const TargetMachine &TM) const {
+static bool isExecuteOnlyFunction(const GlobalObject *GO, SectionKind SK,
+                                  const TargetMachine &TM) {
+  if (const Function *F = dyn_cast<Function>(GO))
+    if (TM.getSubtarget<ARMSubtarget>(*F).genExecuteOnly() && SK.isText())
+      return true;
+  return false;
+}
+
+MCSection *ARMElfTargetObjectFile::getExplicitSectionGlobal(
+    const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const {
   // Set execute-only access for the explicit section
-  if (genExecuteOnly && SK.isText())
+  if (isExecuteOnlyFunction(GO, SK, TM))
     SK = SectionKind::getExecuteOnly();
 
   return TargetLoweringObjectFileELF::getExplicitSectionGlobal(GO, SK, TM);
 }
 
-MCSection *
-ARMElfTargetObjectFile::SelectSectionForGlobal(const GlobalObject *GO,
-                                               SectionKind SK, const TargetMachine &TM) const {
+MCSection *ARMElfTargetObjectFile::SelectSectionForGlobal(
+    const GlobalObject *GO, SectionKind SK, const TargetMachine &TM) const {
   // Place the global in the execute-only text section
-  if (genExecuteOnly && SK.isText())
+  if (isExecuteOnlyFunction(GO, SK, TM))
     SK = SectionKind::getExecuteOnly();
 
   return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, SK, TM);
diff --git a/llvm/lib/Target/ARM/ARMTargetObjectFile.h b/llvm/lib/Target/ARM/ARMTargetObjectFile.h
index dbb8128269d..bd7aa1cfe02 100644
--- a/llvm/lib/Target/ARM/ARMTargetObjectFile.h
+++ b/llvm/lib/Target/ARM/ARMTargetObjectFile.h
@@ -16,8 +16,6 @@
 namespace llvm {
 
 class ARMElfTargetObjectFile : public TargetLoweringObjectFileELF {
-  mutable bool genExecuteOnly = false;
-
 protected:
   const MCSection *AttributesSection = nullptr;