I will file a bug on this.
unsigned short a = 0xaabb;
unsigned int b = 0xaabbccdd;
int main() {
printf("%08x \n", __builtin_bswap16(a));
printf("%08x \n", __builtin_bswap32(b));
}
~/llvmw/build/Debug+Asserts/bin/clang -mllvm -fast-isel -mllvm -fast-isel-verbose bswap1.c -S
bswap1.c:5:3: warning: implicitly declaring library function 'printf' with type
'int (const char *, ...)'
printf("%08x \n", __builtin_bswap16(a));
^
bswap1.c:5:3: note: include the header <stdio.h> or explicitly provide a
declaration for 'printf'
FastISel missed call: %3 = call i32 @llvm.bswap.i32(i32 %2)
FastISel missed call: %1 = call i16 @llvm.bswap.i16(i16 %0)
1 warning generated.
rkotler@ubuntu-rkotler:~/testmips/rt-rk-llvm-tests/tests-c$