Fpret stuff (not very tested).

Test/objc_msgSend.m

@@ -10,6 +10,12 @@ id objc_msgSend(id, SEL, ...);
 
 typedef struct { int a,b,c,d,e; } s;
 s objc_msgSend_stret(id, SEL, ...);
+@interface Fake
+- (int)izero;
+- (float)fzero;
+- (double)dzero;
+- (long double)ldzero;
+@end
 
 Class TestCls;
 @interface Test { id isa; }@end
@@ -70,6 +76,11 @@ int main(void)
 	assert(ret.c == 3);
 	assert(ret.d == 4);
 	assert(ret.e == 5);
+	Fake *f = nil;
+	assert(0 == [f izero]);
+	assert(0 == [f dzero]);
+	assert(0 == [f ldzero]);
+	assert(0 == [f fzero]);
 #ifdef BENCHMARK
 	clock_t c1, c2;
 	c1 = clock();

objc_msgSend.x86-32.S

@@ -56,7 +56,8 @@
 	mov   SLOT_OFFSET(%eax), %eax
 	jmp   *%eax
 4:                                       # returnNil:
-	xor   %eax, %eax
+	xor   %eax, %eax                     # return 0 (int)
+	fldz                                 # return 0 (float)
 	ret
 5:                                       # slowSend:
 	mov   \sel(%esp), %ecx
@@ -82,6 +83,9 @@
 .endm
 .globl objc_msgSend
 	.type	objc_msgSend, @function
+.globl objc_msgSend_fpret
+	.type	objc_msgSend_fpret, @function
+objc_msgSend_fpret:
 objc_msgSend:
 	MSGSEND 4, 8
 .globl objc_msgSend_stret

objc_msgSend.x86-64.S

@@ -60,7 +60,11 @@
 	mov   SLOT_OFFSET(%r10), %r10
 	jmp   *%r10
 4:                                       # returnNil:
-	xor   %rax, %rax
+	                                     # Both of the return registers are
+	                                     # callee-save on x86-64, so we can
+	                                     # return 0 in both in the same code:
+	xor   %rax, %rax                     # Return 0 as an integer
+	pxor  %xmm0, %xmm0                   # Return 0 as a floating point value
 	ret
 5:                                       # slowSend:
 	push  %rax                           # We need to preserve all registers that may contain arguments:
@@ -131,6 +135,9 @@
 .endm
 .globl objc_msgSend
 	.type	objc_msgSend, @function
+.globl objc_msgSend_fpret
+	.type	objc_msgSend_fpret, @function
+objc_msgSend_fpret:
 objc_msgSend:
 	MSGSEND %rdi, %rsi
 .globl objc_msgSend_stret