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Re: Typo or intended?
Bingfeng Mei wrote:
Hello,
I just updated our porting to include last 2-3 weeks of GCC developments. I noticed a large number of test failures at -O1 that use a user-defined data type (based on a special register file of our processor). All variables of such type are now spilled to memory which we don't allow at -O1 because it is too expensive. After investigation, I found that it is the following new code causes the trouble. I don't quite understand the function of the new code, but I don't see what's special for -O1 in terms of register allocation in comparison with higher optimizing levels. If I change it to (optimize < 1), everthing is fine as before. I start to wonder whether (optimize <= 1) is a typo or intended. Thanks in advance.
Sorry for the delay with the answer. I was on vacation last week.
As Andrew Haley guess, it was intended. I thought that improving
debugging for -O1 is also important (more important than optimization).
Although GCC manual says
With `-O', the compiler tries to reduce code size and execution
time, without performing any optimizations that take a great deal
of compilation time.
it also says
`-O' also turns on `-fomit-frame-pointer' on machines where doing
so does not interfere with debugging.
Therefore I've decided to do analogous thing for the patch. May be I am
wrong. We could do this only for -O0 if people really want this which I
am not sure about.
Cheers,
Bingfeng Mei
Broadcom UK
if ((! flag_caller_saves && ALLOCNO_CALLS_CROSSED_NUM (a) != 0)
/* For debugging purposes don't put user defined variables in
callee-clobbered registers. */
|| (optimize <= 1 <--------- why include -O1?
&& (attrs = REG_ATTRS (regno_reg_rtx [ALLOCNO_REGNO (a)])) != NULL
&& (decl = attrs->decl) != NULL
&& VAR_OR_FUNCTION_DECL_P (decl)
&& ! DECL_ARTIFICIAL (decl)))
{
IOR_HARD_REG_SET (ALLOCNO_TOTAL_CONFLICT_HARD_REGS (a),
call_used_reg_set);
IOR_HARD_REG_SET (ALLOCNO_CONFLICT_HARD_REGS (a),
call_used_reg_set);
}
else if (ALLOCNO_CALLS_CROSSED_NUM (a) != 0)
{
IOR_HARD_REG_SET (ALLOCNO_TOTAL_CONFLICT_HARD_REGS (a),
no_caller_save_reg_set);
IOR_HARD_REG_SET (ALLOCNO_TOTAL_CONFLICT_HARD_REGS (a),
temp_hard_reg_set);
IOR_HARD_REG_SET (ALLOCNO_CONFLICT_HARD_REGS (a),
no_caller_save_reg_set);
IOR_HARD_REG_SET (ALLOCNO_CONFLICT_HARD_REGS (a),
temp_hard_reg_set);
}