feat(rtl): migrate blaise_atomic .s to inline asm

runtime/Makefile

@@ -41,13 +41,14 @@ BLAISE       = $(COMPILER_BIN)/blaise
 BLAISE_FLAGS = --no-incremental --assembler internal
 
 # Assembly sources — platform-specific, no C compiler needed.
+# (blaise_atomic migrated to an inline-asm Pascal unit — see blaise_atomic.pas.)
 ASM_OBJS = $(OBJ_DIR)/blaise_start_x86_64.o \
            $(OBJ_DIR)/blaise_setjmp_x86_64.o \
-           $(OBJ_DIR)/blaise_atomic_x86_64.o \
            $(OBJ_DIR)/blaise_utf8_x86_64.o
 
 # Pascal RTL units compiled via the Blaise compiler.
-PAS_OBJS = $(OBJ_DIR)/blaise_mem.o \
+PAS_OBJS = $(OBJ_DIR)/blaise_atomic.o \
+           $(OBJ_DIR)/blaise_mem.o \
            $(OBJ_DIR)/blaise_str.o \
            $(OBJ_DIR)/blaise_set.o \
            $(OBJ_DIR)/blaise_arc.o \
@@ -73,6 +74,10 @@ $(OBJ_DIR)/%.o: $(ASM_DIR)/%.s
 	$(CC) -c -o $@ $<
 
 # --- Pascal unit rules (unit-as-top-level) ---
+$(OBJ_DIR)/blaise_atomic.o: $(PAS_SRC_DIR)/blaise_atomic.pas
+	@mkdir -p $(OBJ_DIR)
+	$(BLAISE) $(BLAISE_FLAGS) --source $< --unit-path $(PAS_SRC_DIR) --output $@
+
 $(OBJ_DIR)/blaise_mem.o: $(PAS_SRC_DIR)/blaise_mem.pas
 	@mkdir -p $(OBJ_DIR)
 	$(BLAISE) $(BLAISE_FLAGS) --source $< --unit-path $(PAS_SRC_DIR) --output $@

runtime/src/main/asm/blaise_atomic_x86_64.s

@@ -1,44 +0,0 @@
-#
-# Blaise — An Object Pascal Compiler
-# Copyright (c) 2026 Graeme Geldenhuys
-# SPDX-License-Identifier: Apache-2.0 WITH Swift-exception
-# Licensed under the Apache License v2.0 with Runtime Library Exception.
-# See LICENSE file in the project root for full license terms.
-#
-# Atomic 32-bit integer operations for ARC thread safety (x86_64).
-#
-# These use the x86 LOCK prefix for full sequential-consistency
-# atomics.  LOCK XADD atomically adds a value to a memory location
-# and returns the previous value in the source register.
-#
-
-.text
-
-# function _AtomicAddInt32(Ptr: PInteger; Delta: Integer): Integer;
-#   %rdi = pointer to 32-bit integer
-#   %esi = value to add
-#   Returns the value BEFORE the addition.
-.globl _AtomicAddInt32
-.type  _AtomicAddInt32, @function
-_AtomicAddInt32:
-    movl %esi, %eax
-    lock xaddl %eax, (%rdi)
-    ret
-.size _AtomicAddInt32, .-_AtomicAddInt32
-
-
-# function _AtomicSubInt32(Ptr: PInteger; Delta: Integer): Integer;
-#   %rdi = pointer to 32-bit integer
-#   %esi = value to subtract
-#   Returns the value BEFORE the subtraction.
-.globl _AtomicSubInt32
-.type  _AtomicSubInt32, @function
-_AtomicSubInt32:
-    negl %esi
-    movl %esi, %eax
-    lock xaddl %eax, (%rdi)
-    ret
-.size _AtomicSubInt32, .-_AtomicSubInt32
-
-
-.section .note.GNU-stack,"",@progbits

runtime/src/main/pascal/blaise_atomic.pas

@@ -0,0 +1,52 @@
+{
+  Blaise - An Object Pascal Compiler
+  Copyright (c) 2026 Graeme Geldenhuys
+  SPDX-License-Identifier: Apache-2.0 WITH Swift-exception
+  Licensed under the Apache License v2.0 with Runtime Library Exception.
+  See LICENSE file in the project root for full license terms.
+}
+
+unit blaise_atomic;
+
+// Atomic 32-bit add/sub primitives used by ARC reference counting.
+//
+// Inline-assembler port of runtime/src/main/asm/blaise_atomic_x86_64.s — the
+// bodies are now `asm … end` routines in this Pascal unit so the RTL builds
+// with Blaise's own internal assembler and needs no hand-written .s file
+// (docs/inline-asm-design.adoc, §"Migration of the .s files").
+//
+// Each returns the PREVIOUS value at Ptr (xadd semantics).  System V AMD64:
+// arg1 Ptr -> %rdi, arg2 Delta -> %esi; the 32-bit result is returned in %eax.
+// `nostackframe` lets the asm body own the frame so the registers hold the
+// raw incoming arguments.
+
+interface
+
+type
+  PInteger = ^Integer;
+
+function _AtomicAddInt32(Ptr: PInteger; Delta: Integer): Integer;
+function _AtomicSubInt32(Ptr: PInteger; Delta: Integer): Integer;
+
+implementation
+
+{ return *Ptr (old); *Ptr += Delta — atomically. }
+function _AtomicAddInt32(Ptr: PInteger; Delta: Integer): Integer;
+  assembler; nostackframe;
+asm
+    movl %esi, %eax
+    lock xaddl %eax, (%rdi)
+    ret
+end;
+
+{ return *Ptr (old); *Ptr -= Delta — atomically (xadd of the negated delta). }
+function _AtomicSubInt32(Ptr: PInteger; Delta: Integer): Integer;
+  assembler; nostackframe;
+asm
+    negl %esi
+    movl %esi, %eax
+    lock xaddl %eax, (%rdi)
+    ret
+end;
+
+end.