https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111835
Bug ID: 111835
Summary: Suboptimal codegen: zero extended load instead of sign
extended one
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: lis8215 at gmail dot com
Target Milestone: ---
In this simplified example:
int test (const uint8_t * src, uint8_t * dst)
{
int8_t tmp = (int8_t)*src;
*dst = tmp;
return tmp;
}
GCC prefers to use load with zero extension instead of more rational sign
extended load.
Then it needs to do explicit sign extension for making return value.
I know there's a lot of bugs related to zero/sign ext, but I guessed it's rare
special case, and it reproduces in any GCC version available at godbolt and any
architecture except x86-64.
