diff options
Diffstat (limited to 'gcc/regclass.c')
| -rw-r--r-- | gcc/regclass.c | 39 |
1 files changed, 38 insertions, 1 deletions
diff --git a/gcc/regclass.c b/gcc/regclass.c index 0af5328effe..e3eca7f35d1 100644 --- a/gcc/regclass.c +++ b/gcc/regclass.c @@ -116,7 +116,16 @@ int n_non_fixed_regs; and are also considered fixed. */ char global_regs[FIRST_PSEUDO_REGISTER]; - + +/* Contains 1 for registers that are set or clobbered by calls. */ +/* ??? Ideally, this would be just call_used_regs plus global_regs, but + for someone's bright idea to have call_used_regs strictly include + fixed_regs. Which leaves us guessing as to the set of fixed_regs + that are actually preserved. We know for sure that those associated + with the local stack frame are safe, but scant others. */ + +HARD_REG_SET regs_invalidated_by_call; + /* Table of register numbers in the order in which to try to use them. */ #ifdef REG_ALLOC_ORDER int reg_alloc_order[FIRST_PSEUDO_REGISTER] = REG_ALLOC_ORDER; @@ -410,6 +419,7 @@ init_reg_sets_1 () CLEAR_HARD_REG_SET (fixed_reg_set); CLEAR_HARD_REG_SET (call_used_reg_set); CLEAR_HARD_REG_SET (call_fixed_reg_set); + CLEAR_HARD_REG_SET (regs_invalidated_by_call); memcpy (call_fixed_regs, fixed_regs, sizeof call_fixed_regs); @@ -428,7 +438,34 @@ init_reg_sets_1 () SET_HARD_REG_BIT (call_fixed_reg_set, i); if (CLASS_LIKELY_SPILLED_P (REGNO_REG_CLASS (i))) SET_HARD_REG_BIT (losing_caller_save_reg_set, i); + + /* There are a couple of fixed registers that we know are safe to + exclude from being clobbered by calls: + + The frame pointer is always preserved across calls. The arg pointer + is if it is fixed. The stack pointer usually is, unless + RETURN_POPS_ARGS, in which case an explicit CLOBBER will be present. + If we are generating PIC code, the PIC offset table register is + preserved across calls, though the target can override that. */ + + if (i == STACK_POINTER_REGNUM || i == FRAME_POINTER_REGNUM) + ; +#if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM + else if (i == HARD_FRAME_POINTER_REGNUM) + ; +#endif +#if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM + else if (i == ARG_POINTER_REGNUM && fixed_regs[i]) + ; +#endif +#ifndef PIC_OFFSET_TABLE_REG_CALL_CLOBBERED + else if (i == PIC_OFFSET_TABLE_REGNUM && flag_pic) + ; +#endif + else if (call_used_regs[i] || global_regs[i]) + SET_HARD_REG_BIT (regs_invalidated_by_call, i); } + memset (contains_reg_of_mode, 0, sizeof (contains_reg_of_mode)); memset (allocatable_regs_of_mode, 0, sizeof (allocatable_regs_of_mode)); for (m = 0; m < (unsigned int) MAX_MACHINE_MODE; m++) |