[AArch64] Support "S" inline assembler constraint

This patch re-introduces the "S" inline assembler constraint. This matches
an absolute symbolic address or a label reference. The primary use case is

asm("adrp %0, %1\n\t"
    "add %0, %0, :lo12:%1" : "=r"(addr) : "S"(&var));

I say re-introduces as it seems like "S" was implemented in the original
AArch64 backend, but it looks like it wasn't carried forward to the merged
backend. The original implementation had A and L modifiers that could be
used to print ":lo12:" to the string. It looks like gcc doesn't use these
and :lo12: is expected to be written in the inline assembly string so I've
not implemented A and L. Clang already supports the S modifier.

Fixes PR37180

Differential Revision: https://reviews.llvm.org/D46745



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332444 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/Target/AArch64/AArch64AsmPrinter.cpp b/lib/Target/AArch64/AArch64AsmPrinter.cpp
index 7788fa5d3cc..f5ee0c46c07 100644
--- a/lib/Target/AArch64/AArch64AsmPrinter.cpp
+++ b/lib/Target/AArch64/AArch64AsmPrinter.cpp
@@ -276,6 +276,11 @@ void AArch64AsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNum,
     printOffset(MO.getOffset(), O);
     break;
   }
+  case MachineOperand::MO_BlockAddress: {
+    MCSymbol *Sym = GetBlockAddressSymbol(MO.getBlockAddress());
+    Sym->print(O, MAI);
+    break;
+  }
   }
 }