[RISCV] MC layer support for the instructions added in the privileged spec

Adds support for the instructions added in the RISC-V privileged ISA
(https://content.riscv.org/wp-content/uploads/2017/05/riscv-privileged-v1.10.pdf):
uret, sret, mret, wfi, and sfence.vma.

Note from the committer: I made very minor formatting changes prior to commit, 
which didn't seem worth creating another review round-trip for.

Differential Revision: https://reviews.llvm.org/D40383

Patch by David Craven.

llvm-svn: 320484

1 files changed, 42 insertions, 0 deletions

diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.td b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
index 9512435cf2f..dcfcccf4960 100644
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
@@ -211,6 +211,11 @@ class ALUW_rr<bits<7> funct7, bits<3> funct3, string opcodestr>
     : RVInstR<funct7, funct3, OPC_OP_32, (outs GPR:$rd),
               (ins GPR:$rs1, GPR:$rs2), opcodestr, "$rd, $rs1, $rs2">;
 
+let hasSideEffects = 1, mayLoad = 0, mayStore = 0 in
+class Priv<string opcodestr, bits<7> funct7>
+    : RVInstR<funct7, 0b000, OPC_SYSTEM, (outs), (ins GPR:$rs1, GPR:$rs2),
+              opcodestr, "">;
+
 //===----------------------------------------------------------------------===//
 // Instructions
 //===----------------------------------------------------------------------===//
@@ -334,6 +339,43 @@ def SRAW  : ALUW_rr<0b0100000, 0b101, "sraw">;
 } // Predicates = [IsRV64]
 
 //===----------------------------------------------------------------------===//
+// Privileged instructions
+//===----------------------------------------------------------------------===//
+
+let isBarrier = 1, isReturn = 1, isTerminator = 1 in {
+def URET : Priv<"uret", 0b0000000> {
+  let rd = 0;
+  let rs1 = 0;
+  let rs2 = 0b00010;
+}
+
+def SRET : Priv<"sret", 0b0001000> {
+  let rd = 0;
+  let rs1 = 0;
+  let rs2 = 0b00010;
+}
+
+def MRET : Priv<"mret", 0b0011000> {
+  let rd = 0;
+  let rs1 = 0;
+  let rs2 = 0b00010;
+}
+} // isBarrier = 1, isReturn = 1, isTerminator = 1
+
+def WFI : Priv<"wfi", 0b0001000> {
+  let rd = 0;
+  let rs1 = 0;
+  let rs2 = 0b00101;
+}
+
+let hasSideEffects = 1, mayLoad = 0, mayStore = 0 in
+def SFENCE_VMA : RVInstR<0b0001001, 0b000, OPC_SYSTEM, (outs),
+                         (ins GPR:$rs1, GPR:$rs2),
+                         "sfence.vma", "$rs1, $rs2"> {
+  let rd = 0;
+}
+
+//===----------------------------------------------------------------------===//
 // Pseudo-instructions and codegen patterns
 //
 // Naming convention: For 'generic' pattern classes, we use the naming