diff --git a/.github/workflows/zjit-macos.yml b/.github/workflows/zjit-macos.yml
index d441d22842e1c4..5517985c1c153c 100644
--- a/.github/workflows/zjit-macos.yml
+++ b/.github/workflows/zjit-macos.yml
@@ -98,7 +98,7 @@ jobs:
           rustup install ${{ matrix.rust_version }} --profile minimal
           rustup default ${{ matrix.rust_version }}
 
-      - uses: taiki-e/install-action@c7eb1735f09259a5035e8e5d44b1406b1cddc0fb # v2.83.0
+      - uses: taiki-e/install-action@43aecc8d72668fbcfe75c31400bc4f890f1c5853 # v2.83.2
         with:
           tool: nextest@0.9
         if: ${{ matrix.test_task == 'zjit-check' }}
diff --git a/.github/workflows/zjit-ubuntu.yml b/.github/workflows/zjit-ubuntu.yml
index 412167da4ed1ba..80c7a0cb7986bf 100644
--- a/.github/workflows/zjit-ubuntu.yml
+++ b/.github/workflows/zjit-ubuntu.yml
@@ -141,7 +141,7 @@ jobs:
           ruby-version: '3.1'
           bundler: none
 
-      - uses: taiki-e/install-action@c7eb1735f09259a5035e8e5d44b1406b1cddc0fb # v2.83.0
+      - uses: taiki-e/install-action@43aecc8d72668fbcfe75c31400bc4f890f1c5853 # v2.83.2
         with:
           tool: nextest@0.9
         if: ${{ matrix.test_task == 'zjit-check' }}
diff --git a/eval_intern.h b/eval_intern.h
index 954ba6a1842484..5e4249e0b87d6c 100644
--- a/eval_intern.h
+++ b/eval_intern.h
@@ -125,9 +125,8 @@ extern int select_large_fdset(int, fd_set *, fd_set *, fd_set *, struct timeval
 
 #define EC_REPUSH_TAG() (void)(_ec->tag = &_tag)
 
-#if defined __GNUC__ && __GNUC__ == 4 && (__GNUC_MINOR__ >= 6 && __GNUC_MINOR__ <= 8) || defined __clang__
-/* This macro prevents GCC 4.6--4.8 from emitting maybe-uninitialized warnings.
- * This macro also prevents Clang from dumping core in EC_EXEC_TAG().
+#if defined __clang__
+/* This macro prevents Clang from dumping core in EC_EXEC_TAG().
  * (I confirmed Clang 4.0.1 and 5.0.0.)
  */
 # define VAR_FROM_MEMORY(var) __extension__(*(__typeof__(var) volatile *)&(var))
diff --git a/iseq.c b/iseq.c
index 65ab43f85635db..720c8f976b5ad5 100644
--- a/iseq.c
+++ b/iseq.c
@@ -1359,8 +1359,8 @@ rb_iseq_compile_with_option(VALUE src, VALUE file, VALUE realpath, VALUE line, V
 {
     rb_iseq_t *iseq = NULL;
     rb_compile_option_t option;
-#if !defined(__GNUC__) || (__GNUC__ == 4 && __GNUC_MINOR__ == 8)
-# define INITIALIZED volatile /* suppress warnings by gcc 4.8 */
+#if !defined(__GNUC__)
+# define INITIALIZED volatile /* suppress warnings */
 #else
 # define INITIALIZED /* volatile */
 #endif
diff --git a/vm_exec.h b/vm_exec.h
index ecf8df3c7da378..0db016ec164f07 100644
--- a/vm_exec.h
+++ b/vm_exec.h
@@ -93,16 +93,7 @@ error !
 /* token threaded code */
 
 /* dispatcher */
-#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)) && __GNUC__ == 3
-#define DISPATCH_ARCH_DEPEND_WAY(addr) \
-  __asm__ __volatile__("jmp *%0;\t# -- inserted by vm.h\t[length = 2]" : : "r" (addr))
-
-#else
-#define DISPATCH_ARCH_DEPEND_WAY(addr) \
-                                /* do nothing */
-#endif
 #define TC_DISPATCH(insn)  \
-  DISPATCH_ARCH_DEPEND_WAY(insns_address_table[GET_CURRENT_INSN()]); \
   INSN_DISPATCH_SIG(insn); \
   RB_GNUC_EXTENSION_BLOCK(goto *insns_address_table[GET_CURRENT_INSN()]); \
   rb_bug("tc error");
diff --git a/win32/setup.mak b/win32/setup.mak
index 19ace3445c2568..db0445302275f7 100644
--- a/win32/setup.mak
+++ b/win32/setup.mak
@@ -160,11 +160,10 @@ main(void)
     return c != value_nan();
 }
 <<
-	@( \
-	  $(CC) -O2 $@.c && .\$@ || \
-	  (set bug=%ERRORLEVEL% & \
-	  echo This compiler has an optimization bug) \
-	) & $(WIN32DIR:/=\)\rm.bat $@.* & exit /b %bug%
+	@($(CC) -O2 $@.c && .\$@) || \
+	  (echo This compiler has an optimization bug & \
+	  $(WIN32DIR:/=\)\rm.bat $@.* & exit /b 1)
+	@$(WIN32DIR:/=\)\rm.bat $@.*
 
 -version-: nul verconf.mk
 
diff --git a/zjit/src/hir.rs b/zjit/src/hir.rs
index e16e7df836d66b..7225fcdc3800bb 100644
--- a/zjit/src/hir.rs
+++ b/zjit/src/hir.rs
@@ -2980,6 +2980,13 @@ impl Function {
         }
     }
 
+    /// Return whether the representative of `insn_id` is a `SendDirect` without
+    /// cloning the instruction or resolving its operands.
+    fn is_send_direct(&self, insn_id: InsnId) -> bool {
+        let insn_id = self.union_find.borrow().find_const(insn_id);
+        matches!(&self.insns[insn_id.0], Insn::SendDirect(..))
+    }
+
     fn new_block(&mut self, insn_idx: u32) -> BlockId {
         let id = BlockId(self.blocks.len());
         let block = Block {
@@ -5062,7 +5069,7 @@ impl Function {
             let mut search_start = 0;
             loop {
                 let Some(offset) = self.blocks[block.0].insns[search_start..].iter()
-                    .position(|&id| matches!(self.find(id), Insn::SendDirect(..)))
+                    .position(|&id| self.is_send_direct(id))
                 else {
                     break;
                 };
@@ -5171,7 +5178,7 @@ impl Function {
                 // pre-Send body, before the PushLightweightFrame and Jump we add
                 // last).
                 let tail = self.blocks[block.0].insns.split_off(send_pos);
-                debug_assert!(matches!(self.find(tail[0]), Insn::SendDirect(..)));
+                debug_assert!(self.is_send_direct(tail[0]));
 
                 let omitted_opt_num = opt_num - passed_opt_num;
                 let positional_kw_end = lead_num + opt_num + rest_slots + post_num + kw_num;