the parisc constraints cannot be found in the Machine Constraints page: http://gcc.gnu.org/onlinedocs/gcc-4.1.1/gcc/Machine-Constraints.html
from gcc/config/pa/: #define REG_CLASS_FROM_LETTER(C) \ ((C) == 'f' ? FP_REGS : \ (C) == 'y' ? FPUPPER_REGS : \ (C) == 'x' ? FP_REGS : \ (C) == 'q' ? SHIFT_REGS : \ (C) == 'a' ? R1_REGS : \ (C) == 'Z' ? ALL_REGS : NO_REGS) -- Summary: parisc-specific asm constraints not documented Product: gcc Version: unknown Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: target AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: vapier at gentoo dot org GCC host triplet: hppa GCC target triplet: hppa http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30760