Add r228939 back with a fix.

The problem in the original patch was not switching back to .text after printing
an eh table.

Original message:

On ELF, put PIC jump tables in a non executable section.

Fixes PR22558.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229586 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

@@ -60,6 +60,9 @@ public:
   getSectionForJumpTable(const Function &F, Mangler &Mang,
                          const TargetMachine &TM) const override;
 
+  bool shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,
+                                           const Function &F) const override;
+
   /// Return an MCExpr to use for a reference to the specified type info global
   /// variable from exception handling information.
   const MCExpr *

include/llvm/Target/TargetLoweringObjectFile.h

@@ -98,6 +98,9 @@ public:
   getSectionForJumpTable(const Function &F, Mangler &Mang,
                          const TargetMachine &TM) const;
 
+  virtual bool shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,
+                                                   const Function &F) const;
+
   /// Targets should implement this method to assign a section to globals with
   /// an explicit section specfied. The implementation of this method can
   /// assume that GV->hasSection() is true.

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -1178,23 +1178,16 @@ void AsmPrinter::EmitJumpTableInfo() {
   // the appropriate section.
   const Function *F = MF->getFunction();
   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
-  bool JTInDiffSection = false;
-  if (// In PIC mode, we need to emit the jump table to the same section as the
-      // function body itself, otherwise the label differences won't make sense.
-      // FIXME: Need a better predicate for this: what about custom entries?
-      MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 ||
-      // We should also do if the section name is NULL or function is declared
-      // in discardable section
-      // FIXME: this isn't the right predicate, should be based on the MCSection
-      // for the function.
-      F->isWeakForLinker()) {
+  bool JTInDiffSection = !TLOF.shouldPutJumpTableInFunctionSection(
+      MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32,
+      *F);
+  if (!JTInDiffSection) {
     OutStreamer.SwitchSection(TLOF.SectionForGlobal(F, *Mang, TM));
   } else {
     // Otherwise, drop it in the readonly section.
     const MCSection *ReadOnlySection =
         TLOF.getSectionForJumpTable(*F, *Mang, TM);
     OutStreamer.SwitchSection(ReadOnlySection);
-    JTInDiffSection = true;
   }
 
   EmitAlignment(Log2_32(

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -359,6 +359,13 @@ const MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
   return getContext().getELFSection(Name, ELF::SHT_PROGBITS, Flags, 0, Group);
 }
 
+bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
+    bool UsesLabelDifference, const Function &F) const {
+  // We can always create relative relocations, so use another section
+  // that can be marked non-executable.
+  return false;
+}
+
 /// getSectionForConstant - Given a mergeable constant with the
 /// specified size and relocation information, return a section that it
 /// should be placed in.

lib/Target/TargetLoweringObjectFile.cpp

@@ -275,6 +275,24 @@ const MCSection *TargetLoweringObjectFile::getSectionForJumpTable(
   return getSectionForConstant(SectionKind::getReadOnly(), /*C=*/nullptr);
 }
 
+bool TargetLoweringObjectFile::shouldPutJumpTableInFunctionSection(
+    bool UsesLabelDifference, const Function &F) const {
+  // In PIC mode, we need to emit the jump table to the same section as the
+  // function body itself, otherwise the label differences won't make sense.
+  // FIXME: Need a better predicate for this: what about custom entries?
+  if (UsesLabelDifference)
+    return true;
+
+  // We should also do if the section name is NULL or function is declared
+  // in discardable section
+  // FIXME: this isn't the right predicate, should be based on the MCSection
+  // for the function.
+  if (F.isWeakForLinker())
+    return true;
+
+  return false;
+}
+
 /// getSectionForConstant - Given a mergable constant with the
 /// specified size and relocation information, return a section that it
 /// should be placed in.

test/CodeGen/X86/global-sections.ll

@@ -3,6 +3,7 @@
 ; RUN: llc < %s -mtriple=i386-apple-darwin10 -relocation-model=static | FileCheck %s -check-prefix=DARWIN-STATIC
 ; RUN: llc < %s -mtriple=x86_64-apple-darwin10 | FileCheck %s -check-prefix=DARWIN64
 ; RUN: llc < %s -mtriple=i386-unknown-linux-gnu -data-sections -function-sections | FileCheck %s -check-prefix=LINUX-SECTIONS
+; RUN: llc < %s -mtriple=x86_64-pc-linux -data-sections -function-sections -relocation-model=pic | FileCheck %s -check-prefix=LINUX-SECTIONS-PIC
 ; RUN: llc < %s -mtriple=i686-pc-win32 -data-sections -function-sections | FileCheck %s -check-prefix=WIN32-SECTIONS
 
 define void @F1() {
@@ -41,6 +42,11 @@ bb5:
 ; LINUX-SECTIONS-NEXT: .cfi_endproc
 ; LINUX-SECTIONS-NEXT: .section        .rodata.F2,"a",@progbits
 
+; LINUX-SECTIONS-PIC: .section        .text.F2,"ax",@progbits
+; LINUX-SECTIONS-PIC: .size   F2,
+; LINUX-SECTIONS-PIC-NEXT: .cfi_endproc
+; LINUX-SECTIONS-PIC-NEXT: .section        .rodata.F2,"a",@progbits
+
 declare void @G()
 
 define void @F3(i32 %y) {