https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67869
Bug ID: 67869
Summary: [SH] Expand some dynamic shifts inline
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: olegendo at gcc dot gnu.org
Target Milestone: ---
Target: sh*-*-*
On SH variants without dynamic shift instructions like shld and shad dynamic
shifts are done via a libcall. For some cases the shift range is known to be
limited, for example:
unsigned int test_0 (unsigned int x, unsigned int y)
{
// valid value for y is 0,1,2,3
// otherwise it's undefined behavior
return x >> (y * 8);
}
unsigned int test_1 (unsigned int x, unsigned int y)
{
// value of y i known to be 0,1,2,3
return x << (y & 3);
}
In such cases a sequence like:
shlr r4
bf .Lx0
shll8 r5
.Lx0:
shlr r4
bf .L0x
shll16 r5
.L0x:
can be expanded inline which is better than the libcall.
