cranelift: Implement br_table on the interpreter

cranelift/filetests/filetests/runtests/br_table.clif

@@ -0,0 +1,148 @@
+test interpret
+test run
+target aarch64
+target s390x
+
+
+function %br_table_i8(i8) -> i8 {
+  jt0 = jump_table [block1, block2, block2, block3]
+
+block0(v0: i8):
+  br_table v0, block4, jt0
+
+block1:
+  v1 = iconst.i8 1
+  jump block5(v1)
+
+block2:
+  v2 = iconst.i8 2
+  jump block5(v2)
+
+block3:
+  v3 = iconst.i8 3
+  jump block5(v3)
+
+block4:
+  v4 = iconst.i8 4
+  jump block5(v4)
+
+block5(v5: i8):
+  v6 = iadd.i8 v0, v5
+  return v6
+}
+; run: %br_table_i8(0) == 1
+; run: %br_table_i8(1) == 3
+; run: %br_table_i8(2) == 4
+; run: %br_table_i8(3) == 6
+; run: %br_table_i8(4) == 8
+; run: %br_table_i8(5) == 9
+; run: %br_table_i8(6) == 10
+; run: %br_table_i8(-1) == 3
+
+
+function %br_table_i16(i16) -> i16 {
+  jt0 = jump_table [block1, block2, block2, block3]
+
+block0(v0: i16):
+  br_table v0, block4, jt0
+
+block1:
+  v1 = iconst.i16 1
+  jump block5(v1)
+
+block2:
+  v2 = iconst.i16 2
+  jump block5(v2)
+
+block3:
+  v3 = iconst.i16 3
+  jump block5(v3)
+
+block4:
+  v4 = iconst.i16 4
+  jump block5(v4)
+
+block5(v5: i16):
+  v6 = iadd.i16 v0, v5
+  return v6
+}
+; run: %br_table_i16(0) == 1
+; run: %br_table_i16(1) == 3
+; run: %br_table_i16(2) == 4
+; run: %br_table_i16(3) == 6
+; run: %br_table_i16(4) == 8
+; run: %br_table_i16(5) == 9
+; run: %br_table_i16(6) == 10
+; run: %br_table_i16(-1) == 3
+
+
+function %br_table_i32(i32) -> i32 {
+  jt0 = jump_table [block1, block2, block2, block3]
+
+block0(v0: i32):
+  br_table v0, block4, jt0
+
+block1:
+  v1 = iconst.i32 1
+  jump block5(v1)
+
+block2:
+  v2 = iconst.i32 2
+  jump block5(v2)
+
+block3:
+  v3 = iconst.i32 3
+  jump block5(v3)
+
+block4:
+  v4 = iconst.i32 4
+  jump block5(v4)
+
+block5(v5: i32):
+  v6 = iadd.i32 v0, v5
+  return v6
+}
+; run: %br_table_i32(0) == 1
+; run: %br_table_i32(1) == 3
+; run: %br_table_i32(2) == 4
+; run: %br_table_i32(3) == 6
+; run: %br_table_i32(4) == 8
+; run: %br_table_i32(5) == 9
+; run: %br_table_i32(6) == 10
+; run: %br_table_i32(-1) == 3
+
+
+function %br_table_i64(i64) -> i64 {
+  jt0 = jump_table [block1, block2, block2, block3]
+
+block0(v0: i64):
+  br_table v0, block4, jt0
+
+block1:
+  v1 = iconst.i64 1
+  jump block5(v1)
+
+block2:
+  v2 = iconst.i64 2
+  jump block5(v2)
+
+block3:
+  v3 = iconst.i64 3
+  jump block5(v3)
+
+block4:
+  v4 = iconst.i64 4
+  jump block5(v4)
+
+block5(v5: i64):
+  v6 = iadd.i64 v0, v5
+  return v6
+}
+; run: %br_table_i64(0) == 1
+; run: %br_table_i64(1) == 3
+; run: %br_table_i64(2) == 4
+; run: %br_table_i64(3) == 6
+; run: %br_table_i64(4) == 8
+; run: %br_table_i64(5) == 9
+; run: %br_table_i64(6) == 10
+; run: %br_table_i64(-1) == 3

cranelift/interpreter/src/interpreter.rs

@@ -217,6 +217,10 @@ impl<'a> State<'a, DataValue> for InterpreterState<'a> {
         self.functions
             .get_from_func_ref(func_ref, self.frame_stack.last().unwrap().function)
     }
+    fn get_current_function(&self) -> &'a Function {
+        self.current_frame().function
+    }
+
     fn push_frame(&mut self, function: &'a Function) {
         self.frame_stack.push(Frame::new(function));
     }

cranelift/interpreter/src/state.rs

@@ -19,6 +19,8 @@ use thiserror::Error;
 pub trait State<'a, V> {
     /// Retrieve a reference to a [Function].
     fn get_function(&self, func_ref: FuncRef) -> Option<&'a Function>;
+    /// Retrieve a reference to the currently executing [Function].
+    fn get_current_function(&self) -> &'a Function;
     /// Record that an interpreter has called into a new [Function].
     fn push_frame(&mut self, function: &'a Function);
     /// Record that an interpreter has returned from a called [Function].
@@ -92,6 +94,10 @@ where
         None
     }
 
+    fn get_current_function(&self) -> &'a Function {
+        unimplemented!()
+    }
+
     fn push_frame(&mut self, _function: &'a Function) {
         unimplemented!()
     }

cranelift/interpreter/src/step.rs

@@ -9,6 +9,7 @@ use cranelift_codegen::ir::{
 };
 use log::trace;
 use smallvec::{smallvec, SmallVec};
+use std::convert::TryFrom;
 use std::ops::RangeFrom;
 use thiserror::Error;
 
@@ -155,10 +156,25 @@ where
         Opcode::BrIcmp => branch_when(icmp(inst.cond_code().unwrap(), &arg(0)?, &arg(1)?)?)?,
         Opcode::Brif => branch_when(state.has_iflag(inst.cond_code().unwrap()))?,
         Opcode::Brff => branch_when(state.has_fflag(inst.fp_cond_code().unwrap()))?,
-        Opcode::BrTable => unimplemented!("BrTable"),
-        Opcode::JumpTableEntry => unimplemented!("JumpTableEntry"),
-        Opcode::JumpTableBase => unimplemented!("JumpTableBase"),
-        Opcode::IndirectJumpTableBr => unimplemented!("IndirectJumpTableBr"),
+        Opcode::BrTable => {
+            if let InstructionData::BranchTable {
+                table, destination, ..
+            } = inst
+            {
+                let jt_data = &state.get_current_function().jump_tables[table];
+
+                // Convert to usize to remove negative indexes from the following operations
+                let jump_target = usize::try_from(arg(0)?.into_int()?)
+                    .ok()
+                    .and_then(|i| jt_data.as_slice().get(i))
+                    .copied()
+                    .unwrap_or(destination);
+
+                ControlFlow::ContinueAt(jump_target, SmallVec::new())
+            } else {
+                unreachable!()
+            }
+        }
         Opcode::Trap => ControlFlow::Trap(CraneliftTrap::User(trap_code())),
         Opcode::Debugtrap => ControlFlow::Trap(CraneliftTrap::Debug),
         Opcode::ResumableTrap => ControlFlow::Trap(CraneliftTrap::Resumable),
@@ -632,6 +648,9 @@ where
         | Opcode::X86Palignr
         | Opcode::X86ElfTlsGetAddr
         | Opcode::X86MachoTlsGetAddr => unimplemented!("x86 instruction: {}", inst.opcode()),
+        Opcode::JumpTableBase | Opcode::JumpTableEntry | Opcode::IndirectJumpTableBr => {
+            unimplemented!("Legacy instruction: {}", inst.opcode())
+        }
     })
 }