Handle isplit when it is not the result of a legalization

cranelift/codegen/src/legalizer/mod.rs

@@ -57,6 +57,31 @@ fn legalize_inst(
         }
     } else if opcode.is_branch() {
         split::simplify_branch_arguments(&mut pos.func.dfg, inst);
+    } else if opcode == ir::Opcode::Isplit {
+        pos.use_srcloc(inst);
+
+        let arg = match pos.func.dfg[inst] {
+            ir::InstructionData::Unary {
+                arg,
+                ..
+            } => pos.func.dfg.resolve_aliases(arg),
+            _ => panic!("Expected isplit: {}", pos.func.dfg.display_inst(inst, None)),
+        };
+
+        let res = pos.func.dfg.inst_results(inst).to_vec();
+        assert_eq!(res.len(), 2);
+        let (resl, resh) = (res[0], res[1]); // Prevent borrowck error
+
+        let curpos = pos.position();
+        let srcloc = pos.srcloc();
+        let (xl, xh) = split::isplit(pos.func, cfg, curpos, srcloc, arg);
+
+        pos.func.dfg.clear_results(inst);
+        pos.remove_inst();
+        pos.func.dfg.change_to_alias(resl, xl);
+        pos.func.dfg.change_to_alias(resh, xh);
+
+        return true;
     }
 
     match pos.func.update_encoding(inst, isa) {

cranelift/filetests/filetests/isa/x86/i128.clif

@@ -1,13 +1,28 @@
 test compile
 target x86_64
 
-function u0:0(i128) -> i128 fast {
-ebb0(v0: i128):
-    v1 = iconst.i64 0
-    v2 = iconst.i64 42
-    v3 = iconcat.i64 v2, v1
-    return v3
-    ; check: v1 = iconst.i64 0
-    ; check: v2 = iconst.i64 42
-    ; check: return v2, v1, v7
+function u0:0(i64, i64) -> i128 fast {
+ebb0(v0: i64, v1: i64):
+;check: ebb0(v0: i64 [%rdi], v1: i64 [%rsi], v3: i64 [%rbp]):
+
+    v2 = iconcat.i64 v0, v1
+    ; check: regmove v0, %rdi -> %rax
+    ; check: regmove v1, %rsi -> %rdx
+
+    return v2
+    ; check: v4 = x86_pop.i64
+    ; check: return v0, v1, v4
+}
+
+function u0:1(i128) -> i64, i64 fast {
+ebb0(v0: i128):
+; check: ebb0(v3: i64 [%rdi], v4: i64 [%rsi], v5: i64 [%rbp]):
+
+    v1, v2 = isplit v0
+    ; check: regmove v3, %rdi -> %rax
+    ; check: regmove v4, %rsi -> %rdx
+
+    return v1, v2
+    ; check: v6 = x86_pop.i64
+    ; check: return v3, v4, v6
 }