https://github.com/libffi/libffi/pull/580

diff --git a/js/src/ctypes/libffi/src/x86/win64.S b/js/src/ctypes/libffi/src/x86/win64.S
index 2c334c82f9b2d..a54459f077c91 100644
--- a/js/src/ctypes/libffi/src/x86/win64.S
+++ b/js/src/ctypes/libffi/src/x86/win64.S
@@ -25,17 +25,17 @@
 
 /* This macro allows the safe creation of jump tables without an
    actual table.  The entry points into the table are all 8 bytes.
    The use of ORG asserts that we're at the correct location.  */
 /* ??? The clang assembler doesn't handle .org with symbolic expressions.  */
 #if defined(__clang__) || defined(__APPLE__) || (defined (__sun__) && defined(__svr4__))
 # define E(BASE, X)	.balign 8
 #else
-# define E(BASE, X)	.balign 8; .org BASE + X * 8
+# define E(BASE, X)	.balign 8; .org BASE + (X) * 8
 #endif
 
 	.text
 
 /* ffi_call_win64 (void *stack, struct win64_call_frame *frame, void *r10)
 
    Bit o trickiness here -- FRAME is the base of the stack frame
    for this function.  This has been allocated by ffi_call.  We also
@@ -102,17 +102,18 @@ E(0b, FFI_TYPE_INT)
 	movq	%rax, (%r8)
 	epilogue
 E(0b, FFI_TYPE_FLOAT)
 	movss	%xmm0, (%r8)
 	epilogue
 E(0b, FFI_TYPE_DOUBLE)
 	movsd	%xmm0, (%r8)
 	epilogue
-E(0b, FFI_TYPE_LONGDOUBLE)
+// FFI_TYPE_LONGDOUBLE may be FFI_TYPE_DOUBLE but we need a different value here.
+E(0b, FFI_TYPE_DOUBLE + 1)
 	call	PLT(C(abort))
 E(0b, FFI_TYPE_UINT8)
 	movzbl	%al, %eax
 	movq	%rax, (%r8)
 	epilogue
 E(0b, FFI_TYPE_SINT8)
 	movsbq	%al, %rax
 	jmp	98f
diff --git a/js/src/ctypes/libffi/src/x86/win64_intel.S b/js/src/ctypes/libffi/src/x86/win64_intel.S
index 7df78b30e42c6..970a4f997a981 100644
--- a/js/src/ctypes/libffi/src/x86/win64_intel.S
+++ b/js/src/ctypes/libffi/src/x86/win64_intel.S
@@ -24,17 +24,17 @@
 
 /* This macro allows the safe creation of jump tables without an
    actual table.  The entry points into the table are all 8 bytes.
    The use of ORG asserts that we're at the correct location.  */
 /* ??? The clang assembler doesn't handle .org with symbolic expressions.  */
 #if defined(__clang__) || defined(__APPLE__) || (defined (__sun__) && defined(__svr4__))
 # define E(BASE, X)	ALIGN 8
 #else
-# define E(BASE, X)	ALIGN 8; ORG BASE + X * 8
+# define E(BASE, X)	ALIGN 8; ORG BASE + (X) * 8
 #endif
 
 	.CODE
 	extern PLT(C(abort)):near
 	extern C(ffi_closure_win64_inner):near
 
 /* ffi_call_win64 (void *stack, struct win64_call_frame *frame, void *r10)
 
@@ -102,17 +102,18 @@ E(0b, FFI_TYPE_INT)
 	mov qword ptr [r8], rax; movq	%rax, (%r8)
 	epilogue
 E(0b, FFI_TYPE_FLOAT)
 	movss dword ptr [r8], xmm0 ; movss	%xmm0, (%r8)
 	epilogue
 E(0b, FFI_TYPE_DOUBLE)
 	movsd qword ptr[r8], xmm0; movsd	%xmm0, (%r8)
 	epilogue
-E(0b, FFI_TYPE_LONGDOUBLE)
+// FFI_TYPE_LONGDOUBLE may be FFI_TYPE_DOUBLE but we need a different value here.
+E(0b, FFI_TYPE_DOUBLE + 1)
 	call	PLT(C(abort))
 E(0b, FFI_TYPE_UINT8)
 	movzx eax, al ;movzbl	%al, %eax
 	mov qword ptr[r8], rax; movq	%rax, (%r8)
 	epilogue
 E(0b, FFI_TYPE_SINT8)
 	movsx rax, al ; movsbq	%al, %rax
 	jmp	L98