[XCOFF][AIX] Fix incorrect alignment for function descriptor csect

[jasonliu]

Summary

Function descriptor csect on AIX should be 4 byte align instead of 1 byte align.

[daltenty]

LGTM

llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp

if (Subtarget->isPPC64()) {
     OutStreamer->emitIntValue(0, 4/*size*/);
     OutStreamer->emitIntValue(0, 8/*size*/);
   }
 }
 
 void PPCAIXAsmPrinter::SetupMachineFunction(MachineFunction &MF) {
   // Get the function descriptor symbol.
   CurrentFnDescSym = getSymbol(&MF.getFunction());
-  // Set the containing csect.
+  // Set the alignment and the containing csect.
   MCSectionXCOFF *FnDescSec = cast<MCSectionXCOFF>(
       getObjFileLowering().getSectionForFunctionDescriptor(CurrentFnDescSym));
+  FnDescSec->setAlignment(Align(Subtarget->isPPC64() ? 8 : 4));
   cast<MCSymbolXCOFF>(CurrentFnDescSym)->setContainingCsect(FnDescSec);
 
   return AsmPrinter::SetupMachineFunction(MF);
 }
 
 void PPCAIXAsmPrinter::ValidateGV(const GlobalVariable *GV) {
   // Early error checking limiting what is supported.
   if (GV->isThreadLocal())

llvm/test/CodeGen/PowerPC/aix-func-dsc-gen.ll

 ; CHECK-NEXT:     Type: 0x0
 ; CHECK-NEXT:     StorageClass: C_HIDEXT (0x6B)
 ; CHECK-NEXT:     NumberOfAuxEntries: 1
 ; CHECK-NEXT:     CSECT Auxiliary Entry {
 ; CHECK-NEXT:       Index: [[#Index+5]]
 ; CHECK-NEXT:       SectionLen: 12
 ; CHECK-NEXT:       ParameterHashIndex: 0x0
 ; CHECK-NEXT:       TypeChkSectNum: 0x0
-; CHECK-NEXT:       SymbolAlignmentLog2: 0
+; CHECK-NEXT:       SymbolAlignmentLog2: 2
 ; CHECK-NEXT:       SymbolType: XTY_SD (0x1)
 ; CHECK-NEXT:       StorageMappingClass: XMC_DS (0xA)
 ; CHECK-NEXT:       StabInfoIndex: 0x0
 ; CHECK-NEXT:       StabSectNum: 0x0
 ; CHECK-NEXT:     }
 ; CHECK-NEXT:   }
 ; CHECK-NEXT:   Symbol {
 ; CHECK-NEXT:     Index: [[#Index+6]]

llvm/test/CodeGen/PowerPC/aix-xcoff-reloc.ll

 ; SYM-NEXT:     Type: 0x0
 ; SYM-NEXT:     StorageClass: C_HIDEXT (0x6B)
 ; SYM-NEXT:     NumberOfAuxEntries: 1
 ; SYM-NEXT:     CSECT Auxiliary Entry {
 ; SYM-NEXT:       Index: 17
 ; SYM-NEXT:       SectionLen: 12
 ; SYM-NEXT:       ParameterHashIndex: 0x0
 ; SYM-NEXT:       TypeChkSectNum: 0x0
-; SYM-NEXT:       SymbolAlignmentLog2: 0
+; SYM-NEXT:       SymbolAlignmentLog2: 2
 ; SYM-NEXT:       SymbolType: XTY_SD (0x1)
 ; SYM-NEXT:       StorageMappingClass: XMC_DS (0xA)
 ; SYM-NEXT:       StabInfoIndex: 0x0
 ; SYM-NEXT:       StabSectNum: 0x0
 ; SYM-NEXT:     }
 ; SYM-NEXT:   }
 ; SYM-NEXT:   Symbol {
 ; SYM-NEXT:     Index: 18