Currently virtually working in PST, not sure if I'll end up in Hawaii or
points further west or not. :-)
This has been around a long long time.
reg_scan_mark_refs counts the number of references to each pseudo in a
function. It has to peek at SET_DEST operands in the off chance that
they might be a STRICT_LOW_PART, SUBREG, or ZERO_EXTRACT which have to
be considered as read-write operands.
A bit of text from the manual in case anyone is unaware of how
ZERO_EXTRACT can appear in a SET_DEST...
table @code
@findex set
@item (set @var{lval} @var{x})
Represents the action of storing the value of @var{x} into the place
represented by @var{lval}. @var{lval} must be an expression
representing a place that can be stored in: @code{reg} (or @code{subreg},
@code{strict_low_part} or @code{zero_extract}), @code{mem}, @code{pc},
@code{parallel}, or @code{cc0}.
[ ... ]
If @var{lval} is a @code{zero_extract}, then the referenced part of
the bit-field (a memory or register reference) specified by the
@code{zero_extract} is given the value @var{x} and the rest of the
bit-field is not changed. Note that @code{sign_extract} can not
appear in @var{lval}.
Unfortunately someone used ZERO_EXTEND rather than ZERO_EXTRACT in the
test for these special case lvalues that are also reads. The
consequences of this goof are tiny, but we might as well fix it.
Georg-Johann noticed this back in 2007, but nobody ever took corrective
action.
Bootstrapped and regression tested on x86_64-unknown-linux-gnu.
Installed on the trunk.
commit acb3ee94191b9d2093e6954a7255758ed8f83125
Author: Jeff Law <l...@redhat.com>
Date: Sat Jan 17 00:19:23 2015 -0700
PR rtl-optimization/32790
* reginfo.c (reg_scan_mark_refs): Look for ZERO_EXTRACT,
not ZERO_EXTEND in SET_DESTs.
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 12bd23a..04ae255 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2015-01-17 Jeff Law <l...@redhat.com>
+
+ PR rtl-optimization/32790
+ * reginfo.c (reg_scan_mark_refs): Look for ZERO_EXTRACT,
+ not ZERO_EXTEND in SET_DESTs.
+
2015-01-17 Alan Modra <amo...@gmail.com>
* cprop.c (do_local_cprop): Revert last change.
diff --git a/gcc/reginfo.c b/gcc/reginfo.c
index 2a18fb8..9015eeb 100644
--- a/gcc/reginfo.c
+++ b/gcc/reginfo.c
@@ -1132,7 +1132,7 @@ reg_scan_mark_refs (rtx x, rtx_insn *insn)
/* Count a set of the destination if it is a register. */
for (dest = SET_DEST (x);
GET_CODE (dest) == SUBREG || GET_CODE (dest) == STRICT_LOW_PART
- || GET_CODE (dest) == ZERO_EXTEND;
+ || GET_CODE (dest) == ZERO_EXTRACT;
dest = XEXP (dest, 0))
;
