[clang]Fix warning for signed conversion on LP64
Currently clang emits warning with -Wconversion for the following code
on LP64 system e.g. x86_64-unknown-linux-gnu:
long foo(long x) {
return 1LL<<x;
}
warning: implicit conversion changes signedness: 'long long' to 'long' [-Wsign-conversion]
return 1ll << x;
~~~~~~ ~~~~^~~~
This does not make sense since all operands are signed.
This patch fixes that to match -m32 and GCC behaviour.
Reviewed by: Fangrui Song
Differential Revision: https://reviews.llvm.org/D144011