rs6000_return_in_memory has:
/* Allow -maltivec -mabi=no-altivec without warning. Altivec vector
modes only exist for GCC vector types if -maltivec. */
if (TARGET_32BIT && !TARGET_ALTIVEC_ABI
&& ALTIVEC_VECTOR_MODE (TYPE_MODE (type)))
return false;
The code below warns for big vectors and returns true. That means a function
returning "__vector int" does so in an AltiVec register with -mabi=altivec, in
r3 r4 r5 r6 with -maltivec only, and in memory without -maltivec.
This means GDB can not tell where the return value goes and whether a reference
argument is necessary, even when it knows whether -mabi=altivec was used.
This comes from here:
http://gcc.gnu.org/ml/gcc-patches/2004-11/msg02035.html
I read through that entire thread and I still don't understand the behavior.
If __vector int should be returned in four GPRs for -maltivec -mabi=no-altivec,
then shouldn't we return it in four GPRs for non-AltiVec configurations too?
In my simpler world, every option either affects the ABI or does not,
-mabi=altivec does, and -maltivec does not.
--
Summary: -maltivec option changes ABI
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: drow at gcc dot gnu dot org
GCC target triplet: powerpc-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33899
