Add RISC-V encodings for copy instructions.

cranelift/filetests/isa/riscv/binary32.cton

@@ -77,6 +77,10 @@ ebb0(v9999: i32):
     [-,%x7]     v140 = iconst.i32 0x12345000            ; bin: 123453b7
     [-,%x16]    v141 = iconst.i32 0xffffffff_fedcb000   ; bin: fedcb837
 
+    ; Copies alias to iadd_imm.
+    [-,%x7]     v150 = copy v1                          ; bin: 00050393
+    [-,%x16]    v151 = copy v2                          ; bin: 000a8813
+
     ; Control Transfer Instructions
 
     ; jal %x1, fn0

lib/cretonne/meta/isa/riscv/encodings.py

@@ -7,7 +7,7 @@ from base.immediates import intcc
 from .defs import RV32, RV64
 from .recipes import OPIMM, OPIMM32, OP, OP32, LUI, BRANCH, JALR, JAL
 from .recipes import LOAD, STORE
-from .recipes import R, Rshamt, Ricmp, I, Iicmp, Iret
+from .recipes import R, Rshamt, Ricmp, I, Iicmp, Iret, Icopy
 from .recipes import U, UJ, UJcall, SB, SBzero, GPsp, GPfi
 from .settings import use_m
 from cdsl.ast import Var
@@ -123,3 +123,8 @@ RV64.enc(base.spill.i64, GPsp, STORE(0b011))
 RV32.enc(base.fill.i32, GPfi, LOAD(0b010))
 RV64.enc(base.fill.i32, GPfi, LOAD(0b010))
 RV64.enc(base.fill.i64, GPfi, LOAD(0b011))
+
+# Register copies.
+RV32.enc(base.copy.i32, Icopy, OPIMM(0b000))
+RV64.enc(base.copy.i64, Icopy, OPIMM(0b000))
+RV64.enc(base.copy.i32, Icopy, OPIMM32(0b000))

lib/cretonne/meta/isa/riscv/recipes.py

@@ -113,6 +113,9 @@ Iicmp = EncRecipe(
 # The variable return values are not encoded.
 Iret = EncRecipe('Iret', MultiAry, size=4, ins=(), outs=())
 
+# Copy of a GPR is implemented as addi x, 0.
+Icopy = EncRecipe('Icopy', Unary, size=4, ins=GPR, outs=GPR)
+
 # U-type instructions have a 20-bit immediate that targets bits 12-31.
 U = EncRecipe(
         'U', UnaryImm, size=4, ins=(), outs=GPR,

lib/cretonne/src/isa/riscv/binemit.rs

@@ -182,6 +182,18 @@ fn recipe_iret<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut CS
           sink);
 }
 
+fn recipe_icopy<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut CS) {
+    if let InstructionData::Unary { arg, .. } = func.dfg[inst] {
+        put_i(func.encodings[inst].bits(),
+              func.locations[arg].unwrap_reg(),
+              0,
+              func.locations[func.dfg.first_result(inst)].unwrap_reg(),
+              sink);
+    } else {
+        panic!("Expected Unary format: {:?}", func.dfg[inst]);
+    }
+}
+
 /// U-type instructions.
 ///
 ///   31  11 6