Fix C call reg alloc bug reported by Noah & Kokubun

2 files changed, 13 insertions, 5 deletions

diff --git a/yjit/src/backend/ir.rs b/yjit/src/backend/ir.rs
index 45d4378eb4..f634fb7678 100644
--- a/yjit/src/backend/ir.rs
+++ b/yjit/src/backend/ir.rs
@@ -633,7 +633,7 @@ impl Assembler
             let reg_index = regs.iter().position(|elem| elem.reg_no == reg.reg_no);
 
             if let Some(reg_index) = reg_index {
-                assert_eq!(*pool & (1 << reg_index), 0);
+                assert_eq!(*pool & (1 << reg_index), 0, "register already allocated");
                 *pool |= 1 << reg_index;
             }
 
@@ -702,7 +702,7 @@ impl Assembler
                 // We do this to improve register allocation on x86
                 // e.g. out  = add(reg0, reg1)
                 //      reg0 = add(reg0, reg1)
-                if opnds.len() > 0 {
+                else if opnds.len() > 0 {
                     if let Opnd::InsnOut{idx, ..} = opnds[0] {
                         if live_ranges[idx] == index {
                             if let Opnd::Reg(reg) = asm.insns[idx].out {
diff --git a/yjit/src/backend/tests.rs b/yjit/src/backend/tests.rs
index dc56bd4abb..a31e16071b 100644
--- a/yjit/src/backend/tests.rs
+++ b/yjit/src/backend/tests.rs
@@ -195,9 +195,7 @@ fn test_base_insn_out()
 fn test_c_call()
 {
     c_callable! {
-        fn dummy_c_fun(v0: usize, v1: usize)
-        {
-        }
+        fn dummy_c_fun(v0: usize, v1: usize) {}
     }
 
     let (mut asm, mut cb) = setup_asm();
@@ -214,6 +212,16 @@ fn test_c_call()
 }
 
 #[test]
+fn test_alloc_ccall_regs() {
+    let mut asm = Assembler::new();
+    let out1 = asm.ccall(0 as *const u8, vec![]);
+    let out2 = asm.ccall(0 as *const u8, vec![out1]);
+    asm.mov(EC, out2);
+    let mut cb = CodeBlock::new_dummy(1024);
+    asm.compile_with_regs(&mut cb, Assembler::get_alloc_regs());
+}
+
+#[test]
 fn test_lea_ret()
 {
     let (mut asm, mut cb) = setup_asm();