and now for something completely different: assembly maybestret-IMPL

forwarding functions for atomicity

1 files changed, 81 insertions, 0 deletions

diff --git a/lib/objc-asm.S b/lib/objc-asm.S
new file mode 100644
index 0000000..d3dae8a
--- /dev/null
+++ b/lib/objc-asm.S
@@ -0,0 +1,81 @@
+/* These all try to re-invoke old_ptr.  To make things worse, we don't know
+ * whether it will be called as stret or not, so we have to guess. */
+.globl _temp_block_invoke
+.section __TEXT,__text,regular,pure_instructions
+#if defined(__x86_64__)
+_temp_block_invoke:
+    push %rcx
+    mov 0x10(%rsi), %rax; /* block if stret, else self */
+    lea _temp_block_invoke(%rip), %rcx
+    cmp %rax, %rcx
+    pop %rcx
+    je 2f
+    mov %rdi, %rax
+    mov %rsi, %rdi
+    mov 0x28(%rax), %rsi
+    mov 0x20(%rax), %rax
+    jmp *(%rax)
+2: /* stret */
+    mov %rsi, %rax
+    mov %rdx, %rsi
+    mov 0x28(%rsi), %rdx
+    mov 0x20(%rsi), %rax
+    jmp *(%rax)
+#elif defined(__i386__)
+_temp_block_invoke:
+    call 1f
+1:
+    pop %edx
+    lea _temp_block_invoke-1b(%edx), %edx
+    mov 8(%esp), %ecx; /* block if stret, else self */
+    mov 0xc(%ecx), %eax
+    cmp %eax, %edx
+    je 2f
+    mov 4(%esp), %eax; /* block */
+    mov %ecx, 4(%esp)
+    mov 0x18(%eax), %ecx
+    mov %ecx, 8(%esp)
+    mov 0x14(%eax), %eax
+    jmp *(%eax)
+2: /* stret */
+    mov 12(%esp), %ecx; /* self */
+    mov 8(%esp), %eax; /* block */
+    mov %ecx, 4(%esp)
+    mov 0x18(%eax), %ecx
+    mov %ecx, 12(%esp)
+    mov 0x14(%eax), %eax
+    jmp *(%eax)
+#elif defined(__arm__)
+.thumb_func _temp_block_invoke
+.thumb
+_temp_block_invoke:
+1:
+    ldr r9, [r1, #0xc]
+    adr r12, 1b
+    cmp r9, r12
+    beq 2f
+    mov r9, r0
+    mov r0, r1
+    ldr r1, [r9, #0x18]
+    ldr r9, [r9, #0x14]
+    ldr r9, [r9]
+    bx r9
+2: /* stret */
+    mov r9, r1
+    mov r1, r2
+    ldr r2, [r9, #0x18]
+    ldr r9, [r9, #0x14]
+    ldr r9, [r9]
+    bx r9
+#elif defined(__arm64__)
+.align 2
+_temp_block_invoke:
+    mov x9, x0
+    mov x0, x1
+    ldr x1, [x9, #0x28]
+    ldr x9, [x9, #0x20]
+    ldr x9, [x9]
+    br x9
+#else
+#error No forwarding assembly definition for this arch
+#endif