Avoid memory dependency between instructions. (ruby#8284)

ioquatix · web-flow · commit 40d774bec68d · 2023-08-25T13:28:33.000+12:00
diff --git a/coroutine/amd64/Context.S b/coroutine/amd64/Context.S
@@ -13,29 +13,35 @@
 .globl PREFIXED_SYMBOL(SYMBOL_PREFIX,coroutine_transfer)
 PREFIXED_SYMBOL(SYMBOL_PREFIX,coroutine_transfer):
 
-	# Save caller state
-	pushq %rbp
-	pushq %rbx
-	pushq %r12
-	pushq %r13
-	pushq %r14
-	pushq %r15
-
-	# Save caller stack pointer
+	# Make space on the stack for 6 registers:
+	subq $48, %rsp
+
+	# Save caller state:
+	movq %rbp, 40(%rsp)
+	movq %rbx, 32(%rsp)
+	movq %r12, 24(%rsp)
+	movq %r13, 16(%rsp)
+	movq %r14, 8(%rsp)
+	movq %r15, (%rsp)
+
+	# Save caller stack pointer:
 	movq %rsp, (%rdi)
 
-	# Restore callee stack pointer
+	# Restore callee stack pointer:
 	movq (%rsi), %rsp
 
 	# Restore callee state
-	popq %r15
-	popq %r14
-	popq %r13
-	popq %r12
-	popq %rbx
-	popq %rbp
-
-	# Put the first argument into the return value
+	movq 40(%rsp), %rbp
+	movq 32(%rsp), %rbx
+	movq 24(%rsp), %r12
+	movq 16(%rsp), %r13
+	movq 8(%rsp), %r14
+	movq (%rsp), %r15
+
+	# Adjust stack pointer back:
+	addq $48, %rsp
+
+	# Put the first argument into the return value:
 	movq %rdi, %rax
 
 	# We pop the return address and jump to it
