Add RISC-V encodings for lui.

This instruction can materialize constants with the low 12 bits clear.

filetests/isa/riscv/binary32.cton

@@ -71,5 +71,9 @@ ebb0:
     [-,%x7]     v132 = icmp_imm ult, v1, 1000  ; bin: 3e853393
     [-,%x16]    v133 = icmp_imm ult, v2, -905  ; bin: c77ab813
 
+    ; lui
+    [-,%x7]     v140 = iconst.i32 0x12345000            ; bin: 123453b7
+    [-,%x16]    v141 = iconst.i32 0xffffffff_fedcb000   ; bin: fedcb837
+
     return
 }

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

@@ -5,8 +5,8 @@ from __future__ import absolute_import
 from base import instructions as base
 from base.immediates import intcc
 from .defs import RV32, RV64
-from .recipes import OPIMM, OPIMM32, OP, OP32
+from .recipes import OPIMM, OPIMM32, OP, OP32, LUI
-from .recipes import JALR, R, Rshamt, Ricmp, I, Iicmp, Iret
+from .recipes import JALR, R, Rshamt, Ricmp, I, Iicmp, Iret, U
 from .settings import use_m
 from cdsl.ast import Var
 
@@ -66,6 +66,11 @@ RV64.enc(base.icmp_imm.i64(intcc.slt, x, y), Iicmp, OPIMM(0b010))
 RV32.enc(base.icmp_imm.i32(intcc.ult, x, y), Iicmp, OPIMM(0b011))
 RV64.enc(base.icmp_imm.i64(intcc.ult, x, y), Iicmp, OPIMM(0b011))
 
+# Integer constants with the low 12 bits clear are materialized by lui.
+RV32.enc(base.iconst.i32, U, LUI())
+RV64.enc(base.iconst.i32, U, LUI())
+RV64.enc(base.iconst.i64, U, LUI())
+
 # "M" Standard Extension for Integer Multiplication and Division.
 # Gated by the `use_m` flag.
 RV32.enc(base.imul.i32, R, OP(0b000, 0b0000001), isap=use_m)

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

@@ -12,6 +12,7 @@ from __future__ import absolute_import
 from cdsl.isa import EncRecipe
 from cdsl.predicates import IsSignedInt
 from base.formats import Binary, BinaryImm, MultiAry, IntCompare, IntCompareImm
+from base.formats import UnaryImm
 from .registers import GPR
 
 # The low 7 bits of a RISC-V instruction is the base opcode. All 32-bit
@@ -72,6 +73,16 @@ def OP32(funct3, funct7):
     return 0b01110 | (funct3 << 5) | (funct7 << 8)
 
 
+def AIUPC():
+    # type: () -> int
+    return 0b00101
+
+
+def LUI():
+    # type: () -> int
+    return 0b01101
+
+
 # R-type 32-bit instructions: These are mostly binary arithmetic instructions.
 # The encbits are `opcode[6:2] | (funct3 << 5) | (funct7 << 8)
 R = EncRecipe('R', Binary, ins=(GPR, GPR), outs=GPR)
@@ -95,3 +106,8 @@ Iicmp = EncRecipe(
 # immediate offset.
 # The variable return values are not encoded.
 Iret = EncRecipe('Iret', MultiAry, ins=GPR, outs=())
+
+# U-type instructions have a 20-bit immediate that targets bits 12-31.
+U = EncRecipe(
+        'U', UnaryImm, ins=(), outs=GPR,
+        instp=IsSignedInt(UnaryImm.imm, 32, 12))

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

@@ -160,3 +160,35 @@ fn recipe_iicmp<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut C
 fn recipe_iret<CS: CodeSink + ?Sized>(_func: &Function, _inst: Inst, _sink: &mut CS) {
     unimplemented!()
 }
+
+/// U-type instructions.
+///
+///   31  11 6
+///   imm rd opcode
+///    12  7      0
+///
+/// Encoding bits: `opcode[6:2] | (funct3 << 5)`
+fn put_u<CS: CodeSink + ?Sized>(bits: u16, imm: i64, rd: RegUnit, sink: &mut CS) {
+    let bits = bits as u32;
+    let opcode5 = bits & 0x1f;
+    let rd = rd as u32 & 0x1f;
+
+    // 0-6: opcode
+    let mut i = 0x3;
+    i |= opcode5 << 2;
+    i |= rd << 7;
+    i |= imm as u32 & 0xfffff000;
+
+    sink.put4(i);
+}
+
+fn recipe_u<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut CS) {
+    if let InstructionData::UnaryImm { imm, .. } = func.dfg[inst] {
+        put_u(func.encodings[inst].bits(),
+              imm.into(),
+              func.locations[func.dfg.first_result(inst)].unwrap_reg(),
+              sink);
+    } else {
+        panic!("Expected UnaryImm format: {:?}", func.dfg[inst]);
+    }
+}