From 40d774bec68de3f252c0b252d9d0303a67bee0cb Mon Sep 17 00:00:00 2001
From: Samuel Williams <samuel.williams@oriontransfer.co.nz>
Date: Fri, 25 Aug 2023 13:28:33 +1200
Subject: [PATCH] Avoid memory dependency between instructions. (#8284)

---
 coroutine/amd64/Context.S | 38 ++++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/coroutine/amd64/Context.S b/coroutine/amd64/Context.S
index d50732adbc..056c276a31 100644
--- 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
+	# Make space on the stack for 6 registers:
+	subq $48, %rsp
 
-	# Save caller stack pointer
+	# 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
+	movq 40(%rsp), %rbp
+	movq 32(%rsp), %rbx
+	movq 24(%rsp), %r12
+	movq 16(%rsp), %r13
+	movq 8(%rsp), %r14
+	movq (%rsp), %r15
 
-	# Put the first argument into the return value
+	# 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