[MC] Pass MCSymbolData to needsRelocateWithSymbol

As discussed in a previous checking to support the .localentry
directive on PowerPC, we need to inspect the actual target symbol
in needsRelocateWithSymbol to make the appropriate decision based
on that symbol's st_other bits.

Currently, needsRelocateWithSymbol does not get the target symbol.
However, it is directly available to its sole caller.  This patch
therefore simply extends the needsRelocateWithSymbol by a new
parameter "const MCSymbolData &SD", passes in the target symbol,
and updates all derived implementations.

In particular, in the PowerPC implementation, this patch removes
the FIXME added by the previous checkin.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213487 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCELFObjectWriter.h

@@ -22,6 +22,7 @@ class MCFragment;
 class MCObjectWriter;
 class MCSectionData;
 class MCSymbol;
+class MCSymbolData;
 class MCValue;
 
 class MCELFObjectTargetWriter {
@@ -54,7 +55,8 @@ public:
   virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                                 bool IsPCRel) const = 0;
 
-  virtual bool needsRelocateWithSymbol(unsigned Type) const;
+  virtual bool needsRelocateWithSymbol(const MCSymbolData &SD,
+                                       unsigned Type) const;
 
   /// @name Accessors
   /// @{

lib/MC/ELFObjectWriter.cpp

@@ -782,7 +782,7 @@ bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
   if (Asm.isThumbFunc(&Sym))
     return true;
 
-  if (TargetObjectWriter->needsRelocateWithSymbol(Type))
+  if (TargetObjectWriter->needsRelocateWithSymbol(*SD, Type))
     return true;
   return false;
 }

lib/MC/MCELFObjectTargetWriter.cpp

@@ -24,6 +24,7 @@ MCELFObjectTargetWriter::MCELFObjectTargetWriter(bool Is64Bit_,
     IsN64(IsN64_){
 }
 
-bool MCELFObjectTargetWriter::needsRelocateWithSymbol(unsigned Type) const {
+bool MCELFObjectTargetWriter::needsRelocateWithSymbol(const MCSymbolData &SD,
+                                                      unsigned Type) const {
   return false;
 }

lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp

@@ -37,7 +37,8 @@ namespace {
     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                           bool IsPCRel) const override;
 
-    bool needsRelocateWithSymbol(unsigned Type) const override;
+    bool needsRelocateWithSymbol(const MCSymbolData &SD,
+                                 unsigned Type) const override;
   };
 }
 
@@ -48,7 +49,8 @@ ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
 
 ARMELFObjectWriter::~ARMELFObjectWriter() {}
 
-bool ARMELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
+bool ARMELFObjectWriter::needsRelocateWithSymbol(const MCSymbolData &SD,
+                                                 unsigned Type) const {
   // FIXME: This is extremelly conservative. This really needs to use a
   // whitelist with a clear explanation for why each realocation needs to
   // point to the symbol, not to the section.

lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp

@@ -30,7 +30,8 @@ namespace {
 
     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                           bool IsPCRel) const override;
-    bool needsRelocateWithSymbol(unsigned Type) const override;
+    bool needsRelocateWithSymbol(const MCSymbolData &SD,
+                                 unsigned Type) const override;
   };
 }
 
@@ -216,7 +217,8 @@ unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target,
 }
 
 bool
-MipsELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
+MipsELFObjectWriter::needsRelocateWithSymbol(const MCSymbolData &SD,
+                                             unsigned Type) const {
   // FIXME: This is extremelly conservative. This really needs to use a
   // whitelist with a clear explanation for why each realocation needs to
   // point to the symbol, not to the section.

lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp

@@ -11,6 +11,7 @@
 #include "MCTargetDesc/PPCFixupKinds.h"
 #include "MCTargetDesc/PPCMCExpr.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/MC/MCELF.h"
 #include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCValue.h"
@@ -31,7 +32,8 @@ namespace {
     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                           bool IsPCRel) const override;
 
-    bool needsRelocateWithSymbol(unsigned Type) const override;
+    bool needsRelocateWithSymbol(const MCSymbolData &SD,
+                                 unsigned Type) const override;
   };
 }
 
@@ -389,16 +391,20 @@ unsigned PPCELFObjectWriter::GetRelocType(const MCValue &Target,
   return getRelocTypeInner(Target, Fixup, IsPCRel);
 }
 
-bool PPCELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
+bool PPCELFObjectWriter::needsRelocateWithSymbol(const MCSymbolData &SD,
+                                                 unsigned Type) const {
   switch (Type) {
     default:
       return false;
 
     case ELF::R_PPC_REL24:
-      // FIXME: We only need to keep the target symbol of the relocation
-      // if the symbol uses a local entry point.  Unfortunately, we do not
-      // have access to the symbol here ...
-      return true;
+      // If the target symbol has a local entry point, we must keep the
+      // target symbol to preserve that information for the linker.
+      // The "other" values are stored in the last 6 bits of the second byte.
+      // The traditional defines for STO values assume the full byte and thus
+      // the shift to pack it.
+      unsigned Other = MCELF::getOther(SD) << 2;
+      return (Other & ELF::STO_PPC64_LOCAL_MASK) != 0;
   }
 }
 

test/MC/PowerPC/ppc64-localentry.s

@@ -27,6 +27,14 @@ caller:
 	nop
 	.size caller, .-caller
 
+	.section .text.other
+caller_other:
+	bl callee1
+	nop
+	bl callee2
+	nop
+	.size caller_other, .-caller_other
+
 # Verify that use of .localentry implies ABI version 2
 # CHECK: ElfHeader {
 # CHECK: Flags [ (0x2)
@@ -38,6 +46,10 @@ caller:
 # CHECK-NEXT: R_PPC64_REL24 callee1
 # CHECK-NEXT: }
 # CHECK-NOT: R_PPC64_REL24 callee2
+# CHECK: Section ({{[0-9]*}}) .rela.text.other {
+# CHECK-NEXT: R_PPC64_REL24 callee1
+# CHECK-NEXT: R_PPC64_REL24 .text
+# CHECK-NEXT: }
 
 # Verify that .localentry is encoded in the Other field.
 # CHECK: Symbols [