Imported Upstream version 6.0.0.172

Former-commit-id: f3cc9b82f3e5bd8f0fd3ebc098f789556b44e9cd

external/llvm/lib/Target/RISCV/RISCVCallingConv.td

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+//===-- RISCVCallingConv.td - Calling Conventions RISCV ----*- tablegen -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This describes the calling conventions for the RISCV architecture.
+//
+//===----------------------------------------------------------------------===//
+
+// The RISC-V calling convention is handled with custom code in
+// RISCVISelLowering.cpp (CC_RISCV).
+
+def CSR : CalleeSavedRegs<(add X1, X3, X4, X8, X9, (sequence "X%u", 18, 27))>;
+
+// Needed for implementation of RISCVRegisterInfo::getNoPreservedMask()
+def CSR_NoRegs : CalleeSavedRegs<(add)>;