ZJIT: Add codegen for FixnumDiv (#15452)

Fixes https://github.com/Shopify/ruby/issues/902

This pull request adds code generation for dividing fixnums.
Testing confirms the normal case, flooring, and side-exiting on division by zero.

jit.c

@@ -761,6 +761,12 @@ rb_jit_fix_mod_fix(VALUE recv, VALUE obj)
     return rb_fix_mod_fix(recv, obj);
 }
 
+VALUE
+rb_jit_fix_div_fix(VALUE recv, VALUE obj)
+{
+    return rb_fix_div_fix(recv, obj);
+}
+
 // YJIT/ZJIT need this function to never allocate and never raise
 VALUE
 rb_yarv_str_eql_internal(VALUE str1, VALUE str2)

test/ruby/test_zjit.rb

@@ -960,6 +960,37 @@ class TestZJIT < Test::Unit::TestCase
     }, call_threshold: 2, insns: [:opt_mult]
   end
 
+  def test_fixnum_div
+    assert_compiles '12', %q{
+      C = 48
+      def test(n) = C / n
+      test(4)
+      test(4)
+    }, call_threshold: 2, insns: [:opt_div]
+  end
+
+  def test_fixnum_floor
+    assert_compiles '0', %q{
+      C = 3
+      def test(n) = C / n
+      test(4)
+      test(4)
+    }, call_threshold: 2, insns: [:opt_div]
+  end
+
+  def test_fixnum_div_zero
+    assert_runs '"divided by 0"', %q{
+      def test(n)
+        n / 0
+      rescue ZeroDivisionError => e
+        e.message
+      end
+
+      test(0)
+      test(0)
+    }, call_threshold: 2, insns: [:opt_div]
+  end
+
   def test_opt_not
     assert_compiles('[true, true, false]', <<~RUBY, insns: [:opt_not])
       def test(obj) = !obj

yjit.c

@@ -292,12 +292,6 @@ rb_yjit_rb_ary_subseq_length(VALUE ary, long beg)
     return rb_ary_subseq(ary, beg, len);
 }
 
-VALUE
-rb_yjit_fix_div_fix(VALUE recv, VALUE obj)
-{
-    return rb_fix_div_fix(recv, obj);
-}
-
 // Return non-zero when `obj` is an array and its last item is a
 // `ruby2_keywords` hash. We don't support this kind of splat.
 size_t

yjit/bindgen/src/main.rs

@@ -368,7 +368,7 @@ fn main() {
         .allowlist_function("rb_str_neq_internal")
         .allowlist_function("rb_yarv_ary_entry_internal")
         .allowlist_function("rb_yjit_ruby2_keywords_splat_p")
-        .allowlist_function("rb_yjit_fix_div_fix")
+        .allowlist_function("rb_jit_fix_div_fix")
         .allowlist_function("rb_jit_fix_mod_fix")
         .allowlist_function("rb_FL_TEST")
         .allowlist_function("rb_FL_TEST_RAW")

yjit/src/cruby.rs

@@ -197,7 +197,7 @@ pub use rb_get_cikw_keywords_idx as get_cikw_keywords_idx;
 pub use rb_get_call_data_ci as get_call_data_ci;
 pub use rb_yarv_str_eql_internal as rb_str_eql_internal;
 pub use rb_yarv_ary_entry_internal as rb_ary_entry_internal;
-pub use rb_yjit_fix_div_fix as rb_fix_div_fix;
+pub use rb_jit_fix_div_fix as rb_fix_div_fix;
 pub use rb_jit_fix_mod_fix as rb_fix_mod_fix;
 pub use rb_FL_TEST as FL_TEST;
 pub use rb_FL_TEST_RAW as FL_TEST_RAW;

yjit/src/cruby_bindings.inc.rs

@@ -1174,7 +1174,6 @@ extern "C" {
     pub fn rb_str_neq_internal(str1: VALUE, str2: VALUE) -> VALUE;
     pub fn rb_ary_unshift_m(argc: ::std::os::raw::c_int, argv: *mut VALUE, ary: VALUE) -> VALUE;
     pub fn rb_yjit_rb_ary_subseq_length(ary: VALUE, beg: ::std::os::raw::c_long) -> VALUE;
-    pub fn rb_yjit_fix_div_fix(recv: VALUE, obj: VALUE) -> VALUE;
     pub fn rb_yjit_ruby2_keywords_splat_p(obj: VALUE) -> usize;
     pub fn rb_yjit_splat_varg_checks(
         sp: *mut VALUE,
@@ -1312,6 +1311,7 @@ extern "C" {
         end: *mut ::std::os::raw::c_void,
     );
     pub fn rb_jit_fix_mod_fix(recv: VALUE, obj: VALUE) -> VALUE;
+    pub fn rb_jit_fix_div_fix(recv: VALUE, obj: VALUE) -> VALUE;
     pub fn rb_yarv_str_eql_internal(str1: VALUE, str2: VALUE) -> VALUE;
     pub fn rb_jit_str_concat_codepoint(str_: VALUE, codepoint: VALUE);
 }

zjit/bindgen/src/main.rs

@@ -279,6 +279,7 @@ fn main() {
         .allowlist_function("rb_jit_mark_unused")
         .allowlist_function("rb_jit_get_page_size")
         .allowlist_function("rb_jit_array_len")
+        .allowlist_function("rb_jit_fix_div_fix")
         .allowlist_function("rb_jit_iseq_builtin_attrs")
         .allowlist_function("rb_jit_str_concat_codepoint")
         .allowlist_function("rb_zjit_iseq_inspect")

zjit/src/codegen.rs

@@ -396,6 +396,7 @@ fn gen_insn(cb: &mut CodeBlock, jit: &mut JITState, asm: &mut Assembler, functio
         Insn::FixnumAdd { left, right, state } => gen_fixnum_add(jit, asm, opnd!(left), opnd!(right), &function.frame_state(*state)),
         Insn::FixnumSub { left, right, state } => gen_fixnum_sub(jit, asm, opnd!(left), opnd!(right), &function.frame_state(*state)),
         Insn::FixnumMult { left, right, state } => gen_fixnum_mult(jit, asm, opnd!(left), opnd!(right), &function.frame_state(*state)),
+        Insn::FixnumDiv { left, right, state } => gen_fixnum_div(jit, asm, opnd!(left), opnd!(right), &function.frame_state(*state)),
         Insn::FixnumEq { left, right } => gen_fixnum_eq(asm, opnd!(left), opnd!(right)),
         Insn::FixnumNeq { left, right } => gen_fixnum_neq(asm, opnd!(left), opnd!(right)),
         Insn::FixnumLt { left, right } => gen_fixnum_lt(asm, opnd!(left), opnd!(right)),
@@ -484,7 +485,6 @@ fn gen_insn(cb: &mut CodeBlock, jit: &mut JITState, asm: &mut Assembler, functio
         Insn::ArrayHash { elements, state } => gen_opt_newarray_hash(jit, asm, opnds!(elements), &function.frame_state(*state)),
         &Insn::IsA { val, class } => gen_is_a(asm, opnd!(val), opnd!(class)),
         &Insn::ArrayMax { state, .. }
-        | &Insn::FixnumDiv { state, .. }
         | &Insn::Throw { state, .. }
         => return Err(state),
     };
@@ -1704,6 +1704,16 @@ fn gen_fixnum_mult(jit: &mut JITState, asm: &mut Assembler, left: lir::Opnd, rig
     asm.add(out_val, Opnd::UImm(1))
 }
 
+/// Compile Fixnum / Fixnum
+fn gen_fixnum_div(jit: &mut JITState, asm: &mut Assembler, left: lir::Opnd, right: lir::Opnd, state: &FrameState) -> lir::Opnd {
+    gen_prepare_leaf_call_with_gc(asm, state);
+
+    // Side exit if rhs is 0
+    asm.cmp(right, Opnd::from(VALUE::fixnum_from_usize(0)));
+    asm.je(side_exit(jit, state, FixnumDivByZero));
+    asm_ccall!(asm, rb_jit_fix_div_fix, left, right)
+}
+
 /// Compile Fixnum == Fixnum
 fn gen_fixnum_eq(asm: &mut Assembler, left: lir::Opnd, right: lir::Opnd) -> lir::Opnd {
     asm.cmp(left, right);

zjit/src/cruby_bindings.inc.rs

@@ -2198,6 +2198,7 @@ unsafe extern "C" {
         start: *mut ::std::os::raw::c_void,
         end: *mut ::std::os::raw::c_void,
     );
+    pub fn rb_jit_fix_div_fix(recv: VALUE, obj: VALUE) -> VALUE;
     pub fn rb_yarv_str_eql_internal(str1: VALUE, str2: VALUE) -> VALUE;
     pub fn rb_jit_str_concat_codepoint(str_: VALUE, codepoint: VALUE);
     pub fn rb_jit_shape_capacity(shape_id: shape_id_t) -> attr_index_t;

zjit/src/hir.rs

@@ -501,6 +501,7 @@ pub enum SideExitReason {
     BlockParamProxyNotIseqOrIfunc,
     StackOverflow,
     FixnumModByZero,
+    FixnumDivByZero,
     BoxFixnumOverflow,
 }
 

zjit/src/stats.rs

@@ -183,6 +183,7 @@ make_counters! {
         exit_fixnum_mult_overflow,
         exit_fixnum_lshift_overflow,
         exit_fixnum_mod_by_zero,
+        exit_fixnum_div_by_zero,
         exit_box_fixnum_overflow,
         exit_guard_type_failure,
         exit_guard_type_not_failure,
@@ -492,6 +493,7 @@ pub fn side_exit_counter(reason: crate::hir::SideExitReason) -> Counter {
         FixnumMultOverflow            => exit_fixnum_mult_overflow,
         FixnumLShiftOverflow          => exit_fixnum_lshift_overflow,
         FixnumModByZero               => exit_fixnum_mod_by_zero,
+        FixnumDivByZero               => exit_fixnum_div_by_zero,
         BoxFixnumOverflow             => exit_box_fixnum_overflow,
         GuardType(_)                  => exit_guard_type_failure,
         GuardTypeNot(_)               => exit_guard_type_not_failure,