This with LAST_UPDATED "Wed Apr 13 18:35:48 UTC 2005", just
after committing CRIS prologue as RTL.
Compare the assembly of the attached file (a pruned version
corresponding to the fp-bit libgcc object _pack_df.o)
compiled at -O2 with to a few minutes before that LAST_UPDATED.
Also observable with -mno-prologue-epilogue as follows:
--- packd.s 2005-04-13 21:13:39.448893527 +0200
+++ packd.s.proepi 2005-04-13 21:13:19.986146213 +0200
@@ -4,6 +4,8 @@
.global ___pack_d
.type ___pack_d, @function
___pack_d:
+ subq 32,$sp
+ movem $r5,[$sp]
move.d [$r10+12],$r2
move.d [$r10+16],$r3
move.d [$r10+4],$r5
@@ -15,21 +17,19 @@ ___pack_d:
beq .L5
cmpq 2,$r9
- beq .L37
- clear.d $r0
-
+ beq .L7
+ nop
test.d $r2
ax
test.d $r3
- beq .L38
- clear.d $r1
-
+ beq .L7
+ nop
move.d [$r10+8],$r4
The first two delay-slots aren't filled any more, when having an RTL prologue
(and epilogue). The unexpected/unwanted difference goes away with
-fno-reorder-blocks. Issue noted here awaiting further investigation.
--
Summary: RTL prologue and basic-block reordering pessimizes
delay-slot filling
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P2
Component: rtl-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hp at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: cris-axis-elf
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21002
