Index: src/runtime/lookup-asm/lookup-asm-x86-elf.S
==================================================================
--- src/runtime/lookup-asm/lookup-asm-x86-elf.S
+++ src/runtime/lookup-asm/lookup-asm-x86-elf.S
@@ -61,13 +61,15 @@
 .endm
 
 .macro generate_lookup_super name lookup
 \name:
 	movl	4(%esp), %edx
-	cmpl	$0, (%edx)
+	movl	(%edx), %eax
+	cmpl	$0, %eax
 	je	ret_nil
 
+	movl	%eax, 4(%esp)
 	movl	4(%edx), %edx
 	movl	32(%edx), %edx
 	jmp	.Lmain_\lookup
 .type \name, %function
 .size \name, .-\name

Index: src/runtime/lookup-asm/lookup-asm-x86-win32.S
==================================================================
--- src/runtime/lookup-asm/lookup-asm-x86-win32.S
+++ src/runtime/lookup-asm/lookup-asm-x86-win32.S
@@ -56,13 +56,15 @@
 .endm
 
 .macro generate_lookup_super name lookup
 \name:
 	movl	4(%esp), %edx
-	cmpl	$0, (%edx)
+	movl	(%edx), %eax
+	cmpl	$0, %eax
 	je	ret_nil
 
+	movl	%eax, 4(%esp)
 	movl	4(%edx), %edx
 	movl	32(%edx), %edx
 	jmp	.Lmain_\lookup
 .endm
 

Index: src/runtime/lookup-asm/lookup-asm-x86_64-elf.S
==================================================================
--- src/runtime/lookup-asm/lookup-asm-x86_64-elf.S
+++ src/runtime/lookup-asm/lookup-asm-x86_64-elf.S
@@ -52,15 +52,16 @@
 .size \name, .-\name
 .endm
 
 .macro generate_lookup_super name lookup
 \name:
-	movq	(%rdi), %rax
-	testq	%rax, %rax
+	movq	%rdi, %r8
+	movq	(%rdi), %rdi
+	testq	%rdi, %rdi
 	jz	ret_nil
 
-	movq	8(%rdi), %r8
+	movq	8(%r8), %r8
 	movq	64(%r8), %r8
 	jmp	.Lmain_\lookup
 .type \name, %function
 .size \name, .-\name
 .endm

Index: src/runtime/lookup-asm/lookup-asm-x86_64-macho.S
==================================================================
--- src/runtime/lookup-asm/lookup-asm-x86_64-macho.S
+++ src/runtime/lookup-asm/lookup-asm-x86_64-macho.S
@@ -48,15 +48,16 @@
 	ret
 .endmacro
 
 .macro generate_lookup_super
 $0:
-	movq	(%rdi), %rax
-	testq	%rax, %rax
+	movq	%rdi, %r8
+	movq	(%rdi), %rdi
+	testq	%rdi, %rdi
 	jz	ret_nil
 
-	movq	8(%rdi), %r8
+	movq	8(%r8), %r8
 	movq	64(%r8), %r8
 	jmp	Lmain_$1
 .endmacro
 
 generate_lookup _objc_msg_lookup, _objc_method_not_found

Index: src/runtime/lookup-asm/lookup-asm-x86_64-win64.S
==================================================================
--- src/runtime/lookup-asm/lookup-asm-x86_64-win64.S
+++ src/runtime/lookup-asm/lookup-asm-x86_64-win64.S
@@ -56,15 +56,16 @@
 	jmp	\not_found
 .endm
 
 .macro generate_lookup_super name lookup
 \name:
-	movq	(%rcx), %rax
-	testq	%rax, %rax
+	movq	%rcx, %r8
+	movq	(%rcx), %rcx
+	testq	%rcx, %rcx
 	jz	ret_nil
 
-	movq	8(%rcx), %r8
+	movq	8(%r8), %r8
 	movq	56(%r8), %r8
 	jmp	.Lmain_\lookup
 .endm
 
 generate_lookup objc_msg_lookup objc_method_not_found