Emit I-type instructions for RISC-V.

These are the BinaryImm formats.

cranelift/filetests/isa/riscv/binary32.cton

@@ -39,5 +39,25 @@ ebb0:
     [-,%x7]             v44 = icmp ult, v1, v2  ; bin: 015533b3
     [-,%x16]            v45 = icmp ult, v2, v1  ; bin: 00aab833
 
+    ; Integer Register-Immediate Instructions
+
+    ; addi
+    [-,%x7]     v100 = iadd_imm v1, 1000       ; bin: 3e850393
+    [-,%x16]    v101 = iadd_imm v2, -905       ; bin: c77a8813
+    ; TBD: slti
+    ; andi
+    [-,%x7]     v110 = band_imm v1, 1000       ; bin: 3e857393
+    [-,%x16]    v111 = band_imm v2, -905       ; bin: c77af813
+    ; ori
+    [-,%x7]     v112 = bor_imm v1, 1000        ; bin: 3e856393
+    [-,%x16]    v113 = bor_imm v2, -905        ; bin: c77ae813
+    ; xori
+    [-,%x7]     v114 = bxor_imm v1, 1000       ; bin: 3e854393
+    [-,%x16]    v115 = bxor_imm v2, -905       ; bin: c77ac813
+
+    ; TBD: slli
+    ; TBD: srli
+    ; TBD: srai
+
     return
 }

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

@@ -66,8 +66,41 @@ fn recipe_rshamt<CS: CodeSink + ?Sized>(_func: &Function, _inst: Inst, _sink: &m
     unimplemented!()
 }
 
-fn recipe_i<CS: CodeSink + ?Sized>(_func: &Function, _inst: Inst, _sink: &mut CS) {
-    unimplemented!()
+/// I-type instructions.
+///
+///   31  19  14     11 6
+///   imm rs1 funct3 rd opcode
+///    20  15     12  7      0
+///
+/// Encoding bits: `opcode[6:2] | (funct3 << 5)`
+fn put_i<CS: CodeSink + ?Sized>(bits: u16, rs1: RegUnit, imm: i64, rd: RegUnit, sink: &mut CS) {
+    let bits = bits as u32;
+    let opcode5 = bits & 0x1f;
+    let funct3 = (bits >> 5) & 0x7;
+    let rs1 = rs1 as u32 & 0x1f;
+    let rd = rd as u32 & 0x1f;
+
+    // 0-6: opcode
+    let mut i = 0x3;
+    i |= opcode5 << 2;
+    i |= rd << 7;
+    i |= funct3 << 12;
+    i |= rs1 << 15;
+    i |= (imm << 20) as u32;
+
+    sink.put4(i);
+}
+
+fn recipe_i<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut CS) {
+    if let InstructionData::BinaryImm { arg, imm, .. } = func.dfg[inst] {
+        put_i(func.encodings[inst].bits(),
+              func.locations[arg].unwrap_reg(),
+              imm.into(),
+              func.locations[func.dfg.first_result(inst)].unwrap_reg(),
+              sink);
+    } else {
+        panic!("Expected Binary format: {:?}", func.dfg[inst]);
+    }
 }
 
 fn recipe_iret<CS: CodeSink + ?Sized>(_func: &Function, _inst: Inst, _sink: &mut CS) {