[AIX] supporting the visibility attribute for aix assembly

SUMMARY:

in the aix assembly , it do not have .hidden and .protected directive.
in current llvm. if a function or a variable which has visibility attribute, it will generate something like the .hidden or .protected , it can not recognize by aix as.
in aix assembly, the visibility attribute are support in the pseudo-op like
.extern Name [ , Visibility ]
.globl Name [, Visibility ]
.weak Name [, Visibility ]

in this patch, we implement the visibility attribute for the global variable, function or extern function .

for example.

extern __attribute__ ((visibility ("hidden"))) int
  bar(int* ip);
__attribute__ ((visibility ("hidden"))) int b = 0;
__attribute__ ((visibility ("hidden"))) int
  foo(int* ip){
   return (*ip)++;
}
the visibility of .comm linkage do not support , we will have a separate patch for it.
we have the unsupported cases ("default" and "internal") , we will implement them in a a separate patch for it.

Reviewers: Jason Liu ,hubert.reinterpretcast,James Henderson

Differential Revision: https://reviews.llvm.org/D75866

4 files changed, 66 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCAsmInfoXCOFF.cpp b/llvm/lib/MC/MCAsmInfoXCOFF.cpp
index bf28dac..4a848426 100644
--- a/llvm/lib/MC/MCAsmInfoXCOFF.cpp
+++ b/llvm/lib/MC/MCAsmInfoXCOFF.cpp
@@ -14,6 +14,7 @@ void MCAsmInfoXCOFF::anchor() {}
 
 MCAsmInfoXCOFF::MCAsmInfoXCOFF() {
   IsLittleEndian = false;
+  HasVisibilityOnlyWithLinkage = true;
   PrivateGlobalPrefix = "L..";
   PrivateLabelPrefix = "L..";
   SupportsQuotedNames = false;
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index df688f4..9a86895 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -171,6 +171,10 @@ public:
   void emitXCOFFLocalCommonSymbol(MCSymbol *LabelSym, uint64_t Size,
                                   MCSymbol *CsectSym,
                                   unsigned ByteAlign) override;
+  void emitXCOFFSymbolLinkageWithVisibility(MCSymbol *Symbol,
+                                            MCSymbolAttr Linakge,
+                                            MCSymbolAttr Visibility) override;
+
   void emitELFSize(MCSymbol *Symbol, const MCExpr *Value) override;
   void emitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                         unsigned ByteAlignment) override;
@@ -791,6 +795,41 @@ void MCAsmStreamer::emitXCOFFLocalCommonSymbol(MCSymbol *LabelSym,
   EmitEOL();
 }
 
+void MCAsmStreamer::emitXCOFFSymbolLinkageWithVisibility(
+    MCSymbol *Symbol, MCSymbolAttr Linkage, MCSymbolAttr Visibility) {
+
+  switch (Linkage) {
+  case MCSA_Global:
+    OS << MAI->getGlobalDirective();
+    break;
+  case MCSA_Weak:
+    OS << MAI->getWeakDirective();
+    break;
+  case MCSA_Extern:
+    OS << "\t.extern\t";
+    break;
+  default:
+    report_fatal_error("unhandled linkage type");
+  }
+
+  Symbol->print(OS, MAI);
+
+  switch (Visibility) {
+  case MCSA_Invalid:
+    // Nothing to do.
+    break;
+  case MCSA_Hidden:
+    OS << ",hidden";
+    break;
+  case MCSA_Protected:
+    OS << ",protected";
+    break;
+  default:
+    report_fatal_error("unexpected value for Visibility type");
+  }
+  EmitEOL();
+}
+
 void MCAsmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
   assert(MAI->hasDotTypeDotSizeDirective());
   OS << "\t.size\t";
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index be5d588..0b650ef 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -1063,6 +1063,14 @@ void MCStreamer::emitXCOFFLocalCommonSymbol(MCSymbol *LabelSym, uint64_t Size,
                                             unsigned ByteAlign) {
   llvm_unreachable("this directive only supported on XCOFF targets");
 }
+
+void MCStreamer::emitXCOFFSymbolLinkageWithVisibility(MCSymbol *Symbol,
+                                                      MCSymbolAttr Linkage,
+                                                      MCSymbolAttr Visibility) {
+  llvm_unreachable("emitXCOFFSymbolLinkageWithVisibility is only supported on "
+                   "XCOFF targets");
+}
+
 void MCStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
 void MCStreamer::emitELFSymverDirective(StringRef AliasName,
                                         const MCSymbol *Aliasee) {}
diff --git a/llvm/lib/MC/MCXCOFFStreamer.cpp b/llvm/lib/MC/MCXCOFFStreamer.cpp
index ad0c2c7..ec9e89f 100644
--- a/llvm/lib/MC/MCXCOFFStreamer.cpp
+++ b/llvm/lib/MC/MCXCOFFStreamer.cpp
@@ -48,12 +48,30 @@ bool MCXCOFFStreamer::emitSymbolAttribute(MCSymbol *Sym,
     Symbol->setStorageClass(XCOFF::C_WEAKEXT);
     Symbol->setExternal(true);
     break;
+  case llvm::MCSA_Hidden:
+    Symbol->setVisibilityType(XCOFF::SYM_V_HIDDEN);
+    break;
+  case llvm::MCSA_Protected:
+    Symbol->setVisibilityType(XCOFF::SYM_V_PROTECTED);
+    break;
   default:
     report_fatal_error("Not implemented yet.");
   }
   return true;
 }
 
+void MCXCOFFStreamer::emitXCOFFSymbolLinkageWithVisibility(
+    MCSymbol *Symbol, MCSymbolAttr Linkage, MCSymbolAttr Visibility) {
+
+  emitSymbolAttribute(Symbol, Linkage);
+
+  // When the caller passes `MCSA_Invalid` for the visibility, do not emit one.
+  if (Visibility == MCSA_Invalid)
+    return;
+
+  emitSymbolAttribute(Symbol, Visibility);
+}
+
 void MCXCOFFStreamer::emitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                        unsigned ByteAlignment) {
   getAssembler().registerSymbol(*Symbol);