https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89154
Bug ID: 89154
Summary: 5% degradation of CPU2006 473.astar starting with
r266305
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pthaugen at gcc dot gnu.org
CC: dje at gcc dot gnu.org, rguenth at gcc dot gnu.org,
segher at gcc dot gnu.org, wschmidt at gcc dot gnu.org
Target Milestone: ---
Host: powerpc64le-unknown-linux-gnu
Target: powerpc64le-unknown-linux-gnu
Build: powerpc64le-unknown-linux-gnu
Not sure if this is really tree-optimization issue, just picked as initial
component since fix dealt with that. Could possibly be
rtl-optimization/shrink-wrap issue brought about by additional register
pressure due to CSE'ing/hoisting some additional code.
Funtion way2obj::releasepoint() degrades 20% starting with r266305. Looking at
perf output, the main difference seems to be that we're no longer
shrink-wrapping the early exit test at the start of the function.
Following is the annotated assembly of the start of the function.
r266304:
--------
0000000010006a40 <_ZN7way2obj12releasepointEii>: /* way2obj::releasepoint(int,
int) total: 2032811 22.9279 */
: 10006a40: lis r2,4098
: 10006a44: addi r2,r2,32512
95384 1.0758 : 10006a48: lwz r9,4424(r3)
: 10006a4c: ld r8,8(r3)
119001 1.3422 : 10006a50: lhz r7,16(r3)
1 1.1e-05 : 10006a54: mullw r9,r9,r5
: 10006a58: add r9,r9,r4
: 10006a5c: extsw r9,r9
169526 1.9121 : 10006a60: rldicr r9,r9,2,61
: 10006a64: lhzx r10,r8,r9
21865 0.2466 : 10006a68: cmpw r10,r7
: 10006a6c: beqlr
r266305:
--------
0000000010006a40 <_ZN7way2obj12releasepointEii>: /* way2obj::releasepoint(int,
int) total: 2440798 26.2354 */
: 10006a40: lis r2,4098
: 10006a44: addi r2,r2,32512
35498 0.3816 : 10006a48: lwa r6,4424(r3)
: 10006a4c: ld r7,8(r3)
26361 0.2833 : 10006a50: std r30,-16(r1)
: 10006a54: mr r30,r3
157660 1.6946 : 10006a58: mfcr r12
162000 1.7413 : 10006a5c: lhz r3,16(r3)
17 1.8e-04 : 10006a60: std r23,-72(r1)
139 0.0015 : 10006a64: mr r23,r4
2 2.1e-05 : 10006a68: mullw r9,r6,r5
59 6.3e-04 : 10006a6c: stw r12,8(r1)
244832 2.6316 : 10006a70: stdu r1,-112(r1)
4 4.3e-05 : 10006a74: add r9,r9,r4
5 5.4e-05 : 10006a78: extsw r9,r9
201 0.0022 : 10006a7c: rldicr r8,r9,2,61
343 0.0037 : 10006a80: add r4,r7,r8
9 9.7e-05 : 10006a84: lhzx r10,r7,r8
151595 1.6294 : 10006a88: cmpw r10,r3
: 10006a8c: beq 10006c64
<_ZN7way2obj12releasepointEii+0x224>
The target of the conditional branch in the slow version is just the epilogue
code to restore R1, R23, R30 and CR3/CR4 and return.
