[RISCV] Add inline asm constraint A for RISC-V

This allows the constraint A to be used in inline asm for RISC-V, which
allows an address held in a register to be used.

This patch adds the minimal amount of code required to get operands with
the right constraints to compile.

Differential Revision: https://reviews.llvm.org/D54295

llvm-svn: 369093

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
index a634ba69f3c..d1166d90df4 100644
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -75,6 +75,10 @@ bool RISCVTargetInfo::validateAsmConstraint(
     // A floating-point register.
     Info.setAllowsRegister();
     return true;
+  case 'A':
+    // An address that is held in a general-purpose register.
+    Info.setAllowsMemory();
+    return true;
   }
 }