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Could not identify that register is clobbered already
- From: "S, Pitchumani" <Pitchumani dot S at atmel dot com>
- To: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, "avr-gcc-list at nongnu dot org" <avr-gcc-list at nongnu dot org>
- Date: Tue, 12 Feb 2013 10:16:02 +0000
- Subject: Could not identify that register is clobbered already
Hi,
I was analyzing an issue for avr target (gcc-4.7.2).
Issue is that already clobbered register is used after the transformation
in post reload pass.
insns after reload pass:
set (reg:HI r24
(const:HI (plus:HI (symbol_ref:HI ("array"))
(const_int 4))
))
...
parallel set (reg:HI r14
(and:HI (reg:HI r14)
(const_int 3)))
clobber:QI r25
...
set (reg:HI r28
(const:HI (plus:HI (symbol_ref:HI ("array"))
(const_int 4))
))
After post reload pass, insn-3 transformed as follows:
set (reg:HI r28
reg:HI r24)
this transformation happened in reload_cse_move2add function.
Since r25 is clobbered in insn-2, above transformation (r28/29 <= r24/25)
become incorrect.
Function 'move2add_use_add3_insn' sets only r24 info for insn-1 instead
of setting info for both r24/25. Function 'validate_change' checks only r24
info for insn-3 transformation.
is it possible to identify clobbered register and avoid transformation?
Regards,
Pitchumani