Add RISC-V encodings for call_indirect.

filetests/isa/riscv/binary32.cton

@@ -4,6 +4,7 @@ isa riscv
 
 function %RV32I(i32 link [%x1]) -> i32 link [%x1] {
     fn0 = function %foo()
+    sig0 = signature()
 
 ebb0(v9999: i32):
     [-,%x10]            v1 = iconst.i32 1
@@ -86,6 +87,10 @@ ebb0(v9999: i32):
     ; jal %x1, fn0
     call fn0()                                  ; bin: Call(fn0) 000000ef
 
+    ; jalr %x1, %x10
+    call_indirect sig0, v1()                    ; bin: 000500e7
+    call_indirect sig0, v2()                    ; bin: 000a80e7
+
     brz v1, ebb3
     brnz v1, ebb1
 

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, Icopy
+from .recipes import R, Rshamt, Ricmp, I, Iicmp, Iret, Icall, Icopy
 from .recipes import U, UJ, UJcall, SB, SBzero, GPsp, GPfi
 from .settings import use_m
 from cdsl.ast import Var
@@ -115,6 +115,8 @@ for inst,           f3 in [
 # is added by legalize_signature().
 RV32.enc(base.x_return, Iret, JALR())
 RV64.enc(base.x_return, Iret, JALR())
+RV32.enc(base.call_indirect.i32, Icall, JALR())
+RV64.enc(base.call_indirect.i64, Icall, JALR())
 
 # Spill and fill.
 RV32.enc(base.spill.i32, GPsp, STORE(0b010))

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

@@ -13,7 +13,8 @@ from cdsl.isa import EncRecipe
 from cdsl.predicates import IsSignedInt
 from cdsl.registers import Stack
 from base.formats import Binary, BinaryImm, MultiAry, IntCompare, IntCompareImm
-from base.formats import Unary, UnaryImm, BranchIcmp, Branch, Jump, Call
+from base.formats import Unary, UnaryImm, BranchIcmp, Branch, Jump
+from base.formats import Call, IndirectCall
 from .registers import GPR
 
 # The low 7 bits of a RISC-V instruction is the base opcode. All 32-bit
@@ -113,6 +114,9 @@ Iicmp = EncRecipe(
 # The variable return values are not encoded.
 Iret = EncRecipe('Iret', MultiAry, size=4, ins=(), outs=())
 
+# I-type encoding for `jalr` as an indirect call.
+Icall = EncRecipe('Icall', IndirectCall, size=4, ins=GPR, outs=())
+
 # Copy of a GPR is implemented as addi x, 0.
 Icopy = EncRecipe('Icopy', Unary, size=4, ins=GPR, outs=GPR)
 

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

@@ -182,6 +182,15 @@ fn recipe_iret<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut CS
           sink);
 }
 
+fn recipe_icall<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut CS) {
+    // Indirect instructions are jalr with rd=%x1.
+    put_i(func.encodings[inst].bits(),
+          func.locations[func.dfg.inst_args(inst)[0]].unwrap_reg(),
+          0, // no offset.
+          1, // rd = %x1: link register.
+          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(),