[RISCV] Add basic support for inline asm constraints

llvm-svn: 322217

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index bd44ab9a138..0dec008a3e9 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -994,3 +994,21 @@ const char *RISCVTargetLowering::getTargetNodeName(unsigned Opcode) const {
   }
   return nullptr;
 }
+
+std::pair<unsigned, const TargetRegisterClass *>
+RISCVTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
+                                                  StringRef Constraint,
+                                                  MVT VT) const {
+  // First, see if this is a constraint that directly corresponds to a
+  // RISCV register class.
+  if (Constraint.size() == 1) {
+    switch (Constraint[0]) {
+    case 'r':
+      return std::make_pair(0U, &RISCV::GPRRegClass);
+    default:
+      break;
+    }
+  }
+
+  return TargetLowering::getRegForInlineAsmConstraint(TRI, Constraint, VT);
+}