[PATCH] D26326: Allow targets to override the use of getKindForGlobal in AsmPrinter to avoid text relocations on PPC64

[Joerg Sonnenberger via llvm-commits]

joerg created this revision.
joerg added reviewers: grosbach, hfinkel.
joerg added a subscriber: llvm-commits.
joerg set the repository for this revision to rL LLVM.
Herald added a subscriber: nemanjai.

getKindForGlobal is currently a static member of TargetLoweringObjectFile and can't be easily customised. One of the more complicated uses is to decide whether a IR constant with relocations can be emitted as constant section.

The default implementation can deal with static vs PIC, but the SYSV ABI for PPC64 is special in that it always requires the PIC rules to be followed. The patch introduces a new method getSectionKindForGlobal with a matching override in the PPC implementation to get the right behavior.


Repository:
  rL LLVM

https://reviews.llvm.org/D26326

Files:
  include/llvm/Target/TargetLoweringObjectFile.h
  lib/CodeGen/AsmPrinter/AsmPrinter.cpp
  lib/Target/PowerPC/PPCTargetObjectFile.cpp
  lib/Target/PowerPC/PPCTargetObjectFile.h
  test/CodeGen/PowerPC/func-addr-consts.ll


Index: test/CodeGen/PowerPC/func-addr-consts.ll
===================================================================
--- test/CodeGen/PowerPC/func-addr-consts.ll
+++ test/CodeGen/PowerPC/func-addr-consts.ll
@@ -0,0 +1,16 @@
+; RUN: llc < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64--linux"
+
+ at g = internal constant i8* bitcast (void ()* @f to i8*), section "gsection", align 8
+ at h = constant i8* bitcast (void ()* @f to i8*), section "hsection", align 8
+ at llvm.used = appending global [2 x i8*] [i8* bitcast (i8** @g to i8*), i8* bitcast (i8** @h to i8*)], section "llvm.metadata"
+
+; Function Attrs: nounwind uwtable
+define internal void @f() {
+entry:
+  ret void
+}
+
+; CHECK: .section	gsection,"aw", at progbits
+; CHECK: .section	hsection,"aw", at progbits
Index: lib/Target/PowerPC/PPCTargetObjectFile.h
===================================================================
--- lib/Target/PowerPC/PPCTargetObjectFile.h
+++ lib/Target/PowerPC/PPCTargetObjectFile.h
@@ -25,6 +25,10 @@
     MCSection *SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind,
                                       const TargetMachine &TM) const override;
 
+    SectionKind getSectionKindForGlobal(const GlobalObject *GO,
+                                        const TargetMachine &TM) const override;
+
+
     /// \brief Describe a TLS variable address within debug info.
     const MCExpr *getDebugThreadLocalSymbol(const MCSymbol *Sym) const override;
   };
Index: lib/Target/PowerPC/PPCTargetObjectFile.cpp
===================================================================
--- lib/Target/PowerPC/PPCTargetObjectFile.cpp
+++ lib/Target/PowerPC/PPCTargetObjectFile.cpp
@@ -48,6 +48,22 @@
   return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
 }
 
+SectionKind PPC64LinuxTargetObjectFile::getSectionKindForGlobal(
+    const GlobalObject *GO, const TargetMachine &TM) const {
+  auto Kind = TargetLoweringObjectFileELF::getSectionKindForGlobal(GO, TM);
+
+  // See in PPC64LinuxTargetObjectFile::SelectSectionForGlobal above.
+  if (Kind.isReadOnly()) {
+    const auto *GVar = dyn_cast<GlobalVariable>(GO);
+
+    if (GVar && GVar->isConstant() && GVar->getInitializer()->needsRelocation())
+      Kind = SectionKind::getReadOnlyWithRel();
+  }
+
+  return Kind;
+}
+
+
 const MCExpr *PPC64LinuxTargetObjectFile::
 getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
   const MCExpr *Expr =
Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -388,7 +388,8 @@
   if (MAI->hasDotTypeDotSizeDirective())
     OutStreamer->EmitSymbolAttribute(EmittedSym, MCSA_ELF_TypeObject);
 
-  SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, TM);
+  const TargetLoweringObjectFile &TLOF = getObjFileLowering();
+  SectionKind GVKind = TLOF.getSectionKindForGlobal(GV, TM);
 
   const DataLayout &DL = GV->getParent()->getDataLayout();
   uint64_t Size = DL.getTypeAllocSize(GV->getType()->getElementType());
Index: include/llvm/Target/TargetLoweringObjectFile.h
===================================================================
--- include/llvm/Target/TargetLoweringObjectFile.h
+++ include/llvm/Target/TargetLoweringObjectFile.h
@@ -89,6 +89,11 @@
   static SectionKind getKindForGlobal(const GlobalObject *GO,
                                       const TargetMachine &TM);
 
+  virtual SectionKind getSectionKindForGlobal(const GlobalObject *GO,
+                                              const TargetMachine &TM) const {
+    return TargetLoweringObjectFile::getKindForGlobal(GO, TM);
+  }
+
   /// This method computes the appropriate section to emit the specified global
   /// variable or function definition. This should not be passed external (or
   /// available externally) globals.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D26326.76973.patch
Type: text/x-patch
Size: 3921 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20161105/b6d97204/attachment.bin>