In x86 assembly almost all multiplication operations return a result double the width of the inputs: http://www.aldeid.com/wiki/X86-assembly/Instructions/mul
Checking for overflow is just a matter of testing if the high-order bits are zero.
Checking for overflow is just a matter of testing if the high-order bits are zero.
Here's an example where there is overflow, but your suggestion would not catch it:
mov eax, 0x7fffffff
mov ecx, 2
imul ecx ; edx:eax = eax * ecx
; edx = 0
; eax = 0xfffffffe
; overflow flag = 1
There are also issues with detecting overflow of SSE multiplies (signed and unsigned).
C has some interesting gaps for something that's long been described as a macro for assembly. A rotate operator would also be nice.