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subreg_get_info vs mode restrictions in registers?
- From: DJ Delorie <dj at redhat dot com>
- To: gcc at gcc dot gnu dot org
- Date: Wed, 24 Jan 2007 15:41:54 -0500
- Subject: subreg_get_info vs mode restrictions in registers?
subreg_get_inf() in rtlanal.c blindly assumes that any hard register
can hold any smaller-than-native mode:
nregs_ymode = hard_regno_nregs[xregno][ymode];
. . .
&& (GET_MODE_SIZE (ymode) % nregs_ymode) == 0)
However, there are registers in m32c that cannot hold a QImode value.
By this, I mean there are NO opcodes that deal with a QImode subset of
the 16 bits in $r2 or $r3.
So which assumption is valid: that there can be registers that cannot
be subreg'd, or that all registers can be subreg'd?