Initial effort to support 32-bit Linux.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65847 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.ac

@@ -2332,6 +2332,11 @@ AS_CASE(["$target_cpu-$target_os"],
     AC_DEFINE(FIBER_USE_COROUTINE, "coroutine/amd64/Context.h")
     AC_LIBOBJ([coroutine/amd64/Context])
   ],
+  [*86-*], [
+    AC_MSG_RESULT(x86)
+    AC_DEFINE(FIBER_USE_COROUTINE, "coroutine/x86/Context.h")
+    AC_LIBOBJ([coroutine/x86/Context])
+  ]
   [*], [
     AC_MSG_RESULT(no)
   ]

coroutine/x86/Context.h

@@ -0,0 +1,61 @@
+//
+//  File file is part of the "Coroutine" project and released under the MIT License.
+//
+//  Created by Samuel Williams on 3/11/2018.
+//  Copyright, 2018, by Samuel Williams. All rights reserved.
+//
+
+#pragma once
+
+#include <assert.h>
+#include <string.h>
+
+#if __cplusplus
+extern "C" {
+#endif
+
+#define COROUTINE void __attribute__((fastcall))
+
+const size_t COROUTINE_REGISTERS = 4;
+
+// The fiber context (stack pointer).
+typedef struct
+{
+	void **stack_pointer;
+} coroutine_context;
+
+// The initialization function.
+typedef void(* coroutine_start)(coroutine_context *from, coroutine_context *self) __attribute__((fastcall));
+
+void coroutine_initialize(
+	coroutine_context *context,
+	coroutine_start start,
+	void *stack_pointer,
+	size_t stack_size
+) {
+	/* Force 16-byte alignment */
+	context->stack_pointer = (void**)((uintptr_t)stack_pointer & ~0xF);
+
+	if (!start) {
+		assert(!context->stack_pointer);
+		/* We are main coroutine for this thread */
+		return;
+	}
+
+	*--context->stack_pointer = NULL;
+	*--context->stack_pointer = (void*)start;
+
+	context->stack_pointer -= COROUTINE_REGISTERS;
+	memset(context->stack_pointer, 0, sizeof(void*) * COROUTINE_REGISTERS);
+}
+
+coroutine_context * coroutine_transfer(coroutine_context * current, coroutine_context * target) __attribute__((fastcall));
+
+inline void coroutine_destroy(coroutine_context * context)
+{
+	context->stack_pointer = NULL;
+}
+
+#if __cplusplus
+}
+#endif

coroutine/x86/Context.s

@@ -0,0 +1,39 @@
+##
+##  File file is part of the "Coroutine" project and released under the MIT License.
+##
+##  Created by Samuel Williams on 3/11/2018.
+##  Copyright, 2018, by Samuel Williams. All rights reserved.
+##
+
+.text
+
+.globl coroutine_transfer
+coroutine_transfer:
+
+# For older linkers
+.globl _coroutine_transfer
+_coroutine_transfer:
+
+	# Save caller registers
+	pushl %ebp
+	pushl %ebx
+	pushl %edi
+	pushl %esi
+
+	# Save caller stack pointer
+	movl %esp, (%ecx)
+
+	# Restore callee stack pointer
+	movl (%edx), %esp
+
+	# Restore callee stack
+	popl %esi
+	popl %edi
+	popl %ebx
+	popl %ebp
+
+	# Save the first argument as the return value
+	movl %ecx, %eax
+
+	# Jump to the address on the stack
+	ret