------- Comment #8 from janis at gcc dot gnu dot org 2008-02-07 02:04 -------
Some experimentation shows how GCC is passing and returning non-hardware
vectors for powerpc*-linux:
-m32 (for trunk and 4.0)
pass struct by reference (copy in caller's frame)
return struct in memory using address in hidden first argument
-mno-altivec -mabi=no-altivec pass vector argument by reference
-mno-altivec -mabi=no-altivec return vector result via hidden arg 1
-maltivec -mabi=no-altivec pass vector argument by reference
-maltivec -mabi=no-altivec return vector result in r3-r6
-mno-altivec -mabi=altivec pass vector argument in caller's frame
-mno-altivec -mabi=altivec return vector result in r3-r6
-m64
pass struct in argument registers
return struct in memory using address in hidden first argument
-mno-altivec -mabi=altivec pass vector argument in caller's frame
-mno-altivec -mabi=altivec return vector result in r3-r4
[processing -mabi=no-altivec has been broken since 4.1]
-m64 with 4.0
-mno-altivec -mabi=no-altivec pass vector argument by reference
-mno-altivec -mabi=no-altivec return vector result via hidden arg 1
-maltivec -mabi=no-altivec pass vector argument by reference
-maltivec -mabi=no-altivec return vector result via hidden arg 1
-mno-altivec -mabi=altivec pass vector argument in caller's frame
-mno-altivec -mabi=altivec return vector result in r3-r4
This is a mess. I'd like to change the -m32 behavior to pass non-hardware
vectors by reference and to return them via a pointer in the hidden first
argument. For -m64 I'd return them via a pointer in the hidden first argument,
but I'm not sure whether to pass them by reference, or in argument registers
like aggregates. Suggestions?
--
janis at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jsm28 at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34526
