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Re: New target macro HARD_REGNO_CALL_PART_CLOBBERED
- To: law at cygnus dot com
- Subject: Re: New target macro HARD_REGNO_CALL_PART_CLOBBERED
- From: Michael Hayes <m dot hayes at elec dot canterbury dot ac dot nz>
- Date: Thu, 01 Oct 1998 12:52:12 +1200 (NZST)
- Cc: Michael Hayes <m dot hayes at elec dot canterbury dot ac dot nz>, egcs-patches at cygnus dot com
- References: <"13840.43544.900286.239959"@ongaonga.elec.canterbury.ac.nz><firstname.lastname@example.org>
Jeffrey A Law writes:
> Is this to deal with the high 8 bits in a 40bit register or
> something similar?
In this case yes. Some of the call saved 40 bit registers have only
the 32 MSBs preserved, while others only have the 32 LSBs preserved.
The patch may also be applicable for a target that only preserves
the 16 LSBs of a 32 bit register across a call. In this case, GCC
could allocate a QImode or HImode quantity to a pseudo that crosses
the call, but not a SImode quantity.