Simplify jump table instructions and add missing conversion;

This makes non-legalized jump table instructions operate on operands with
pointer-sized types. This means we need to extend smaller types into the
pointer-sized operand, when the two don't match.

cranelift/codegen/meta/src/isa/x86/encodings.rs

@@ -1224,13 +1224,10 @@ pub fn define(
 
     // Jump tables.
     e.enc64(
-        jump_table_entry.bind(I64).bind_any().bind_any(),
+        jump_table_entry.bind(I64),
         rec_jt_entry.opcodes(vec![0x63]).rex().w(),
     );
-    e.enc32(
-        jump_table_entry.bind(I32).bind_any().bind_any(),
-        rec_jt_entry.opcodes(vec![0x8b]),
-    );
+    e.enc32(jump_table_entry.bind(I32), rec_jt_entry.opcodes(vec![0x8b]));
 
     e.enc64(
         jump_table_base.bind(I64),

cranelift/codegen/meta/src/shared/instructions.rs

@@ -269,15 +269,9 @@ pub fn define(
         .is_branch(true),
     );
 
+    // The index into the br_table can be any type; legalizer will convert it to the right type.
     let x = &operand_doc("x", iB, "index into jump table");
-
-    let Entry = &TypeVar::new(
-        "Entry",
-        "A scalar integer type",
-        TypeSetBuilder::new().ints(Interval::All).build(),
-    );
-
-    let entry = &operand_doc("entry", Entry, "entry of jump table");
+    let entry = &operand_doc("entry", iAddr, "entry of jump table");
     let JT = &operand("JT", jump_table);
 
     ig.push(
@@ -305,6 +299,9 @@ pub fn define(
         .is_branch(true),
     );
 
+    // These are the instructions which br_table legalizes to: they perform address computations,
+    // using pointer-sized integers, so their type variables are more constrained.
+    let x = &operand_doc("x", iAddr, "index into jump table");
     let Size = &operand_doc("Size", uimm8, "Size in bytes");
 
     ig.push(

cranelift/codegen/src/legalizer/mod.rs

@@ -240,29 +240,34 @@ fn expand_br_table_jt(
     //     $addr = iadd $base, $rel_addr
     //     indirect_jump_table_br $addr, $jt
 
-    let table_size = func.jump_tables[table].len();
-    let addr_ty = isa.pointer_type();
-    let entry_ty = I32;
-
     let ebb = func.layout.pp_ebb(inst);
     let jump_table_ebb = func.dfg.make_ebb();
 
     let mut pos = FuncCursor::new(func).at_inst(inst);
     pos.use_srcloc(inst);
 
-    // Bounds check
+    // Bounds check.
+    let table_size = pos.func.jump_tables[table].len() as i64;
     let oob = pos
         .ins()
-        .icmp_imm(IntCC::UnsignedGreaterThanOrEqual, arg, table_size as i64);
+        .icmp_imm(IntCC::UnsignedGreaterThanOrEqual, arg, table_size);
 
     pos.ins().brnz(oob, default_ebb, &[]);
     pos.ins().jump(jump_table_ebb, &[]);
     pos.insert_ebb(jump_table_ebb);
 
+    let addr_ty = isa.pointer_type();
+
+    let arg = if pos.func.dfg.value_type(arg) == addr_ty {
+        arg
+    } else {
+        pos.ins().uextend(addr_ty, arg)
+    };
+
     let base_addr = pos.ins().jump_table_base(addr_ty, table);
     let entry = pos
         .ins()
-        .jump_table_entry(addr_ty, arg, base_addr, entry_ty.bytes() as u8, table);
+        .jump_table_entry(arg, base_addr, I32.bytes() as u8, table);
 
     let addr = pos.ins().iadd(base_addr, entry);
     pos.ins().indirect_jump_table_br(addr, table);

cranelift/filetests/filetests/isa/x86/legalize-br-table.clif

@@ -16,8 +16,9 @@ ebb0(v0: i64):
 ; nextln:    brif uge $oob, ebb2
 ; nextln:    fallthrough $(inb=$EBB)
 ; check:   $inb:
+; nextln:    $(final_idx=$V) = uextend.i64 $idx
 ; nextln:    $(base=$V) = jump_table_base.i64 jt0
-; nextln:    $(rel_addr=$V) = jump_table_entry.i64 $idx, $base, 4, jt0
+; nextln:    $(rel_addr=$V) = jump_table_entry $final_idx, $base, 4, jt0
 ; nextln:    $(addr=$V) = iadd $base, $rel_addr
 ; nextln:    indirect_jump_table_br $addr, jt0
 

cranelift/filetests/filetests/licm/jump-table-entry.clif

@@ -14,7 +14,7 @@ ebb1: ; the loop!
     fallthrough ebb2
 
 ebb2:
-    v1 = iconst.i32 -14
+    v1 = iconst.i64 -14
     v8 = ifcmp_imm v1, 2
     brif uge v8, ebb1
     jump ebb3
@@ -25,7 +25,7 @@ ebb3:
     v7 = iadd v5, v6
     indirect_jump_table_br v7, jt0
 ; check: ebb2:
-; nextln: v8 = ifcmp_imm.i32 v1, 2
+; nextln: v8 = ifcmp_imm.i64 v1, 2
 ; nextln: brif uge v8, ebb1
 ; nextln: jump ebb3
 ; check: ebb3: