[RISCV] Add instruction definition for dret

Summary:
The instruction dret is used to return from debug mode and is defined in the
RISC-V debug mode spec.

https://github.com/riscv/riscv-opcodes/blob/master/opcodes-system

Reviewers: apazos, asb, lenary, luismarques

Reviewed By: apazos

Subscribers: jfb, hiraditya, rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, jrtc27, MaskRay, zzheng, edward-jones, rogfer01, MartinMosbeck, brucehoult, the_o, rkruppe, PkmX, jocewei, psnobl, benna, Jim, s.egerton, sameer.abuasal, evandro, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78583

diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfo.td b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
index 28b175a..1f75dd1 100644 (file)
--- a/llvm/lib/Target/RISCV/RISCVInstrInfo.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfo.td
@@ -589,6 +589,18 @@ def SFENCE_VMA : RVInstR<0b0001001, 0b000, OPC_SYSTEM, (outs),
 }
 
 //===----------------------------------------------------------------------===//
+// Debug instructions
+//===----------------------------------------------------------------------===//
+
+let isBarrier = 1, isReturn = 1, isTerminator = 1 in {
+def DRET : Priv<"dret", 0b0111101>, Sched<[]> {
+  let rd = 0;
+  let rs1 = 0;
+  let rs2 = 0b10010;
+}
+} // isBarrier = 1, isReturn = 1, isTerminator = 1
+
+//===----------------------------------------------------------------------===//
 // Assembler Pseudo Instructions (User-Level ISA, Version 2.2, Chapter 20)
 //===----------------------------------------------------------------------===//
 

diff --git a/llvm/test/MC/RISCV/debug-valid.s b/llvm/test/MC/RISCV/debug-valid.s
new file mode 100644 (file)
index 0000000..89b8f00
--- /dev/null
+++ b/llvm/test/MC/RISCV/debug-valid.s
@@ -0,0 +1,14 @@
+# RUN: llvm-mc %s -triple=riscv32 -riscv-no-aliases -show-encoding \
+# RUN:     | FileCheck -check-prefixes=CHECK,CHECK-INST %s
+# RUN: llvm-mc %s -triple=riscv64 -riscv-no-aliases -show-encoding \
+# RUN:     | FileCheck -check-prefixes=CHECK,CHECK-INST %s
+# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
+# RUN:     | llvm-objdump -M no-aliases -d - \
+# RUN:     | FileCheck -check-prefix=CHECK-INST %s
+# RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
+# RUN:     | llvm-objdump -M no-aliases -d - \
+# RUN:     | FileCheck -check-prefix=CHECK-INST %s
+
+# CHECK-INST: dret
+# CHECK: encoding: [0x73,0x00,0x20,0x7b]
+dret