I have this code:
void conv(long *pa, signed char b)
*pa = static_cast<long>(b);
GCC 4.3.4 on SLES11, aswell as a recent GCC 4.7.1 compile this to:
movsbq %sil, %rsi
movq %rsi, (%rdi)
So the "signed char b" in sil is sign-extended to a 64 bit register.
clang emits this:
# BB#0: # %entry
movslq %esi, %rax
movq %rax, (%rdi)
clang is already passing char arguments in 32-bit registers sign-extended, and the generated code of this function relies on that. I have a case where this causes problems with jitted code that is calling such functions, and the assumption made by clang that the char has already been extended to 32 bit fails there.
Anyone can shine some light on this?
Thanks and best regards,