https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99228
Bug ID: 99228
Summary: blend/shuffle
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
Hello ggc team,
the compiler generates very inefficient code for the sgn functions (scalar and
complex arguments)
https://godbolt.org/z/zvE3Mf
scalar
- float32/64: 2 conditional jumps instead of blend/shuffle
- float80: no fcmov
- integer: only cmov instead of blend/shuffle
complex
- float32/64: 4 conditional jumps instead of blend/shuffle
- float80: no fcmov
- integer: only cmov instead of blend/shuffle
For testing I have 3 versions each:
v1: total disaster
v2: better, only half of the jumps each time, but clang can't really handle
that
v3: like v2, but clang seems to work too. If you remove [[likely]] from
conditional_move like v1.
regards
Gero
