[HACKERS] powerpc(32) point/polygon regression failures on Debian Jessie

The point/polygon regression tests have started to fail on 32-bit
powerpc on Debian Jessie. So far I could reproduce the problem with
PostgreSQL 9.4.10+11 and 9.6.1, on several different machines. Debian
unstable is unaffected.

The failure looks like this:

https://buildd.debian.org/status/fetch.php?pkg=postgresql-9.6&arch=powerpc&ver=9.6.1-2~bpo8%2B1&stamp=1485184696&raw=0

******** build/src/test/regress/regression.diffs ********
*** /«PKGBUILDDIR»/build/../src/test/regress/expected/point.out    Mon Oct 24 20:08:51 2016
--- /«PKGBUILDDIR»/build/src/test/regress/results/point.out    Mon Jan 23 15:17:51 2017
***************
*** 125,131 ****      | (-3,4)     |                5      | (-10,0)    |               10      | (-5,-12)   |
    13
 
!      | (10,10)    |  14.142135623731      | (5.1,34.5) | 34.8749193547455 (6 rows) 
--- 125,131 ----      | (-3,4)     |                5      | (-10,0)    |               10      | (-5,-12)   |
    13
 
!      | (10,10)    | 14.1421356237309      | (5.1,34.5) | 34.8749193547455 (6 rows) 
***************
*** 150,157 ****            | (-5,-12)   | (-10,0)    |               13            | (-5,-12)   | (0,0)      |
     13            | (0,0)      | (-5,-12)   |               13
 
!            | (0,0)      | (10,10)    |  14.142135623731
!            | (10,10)    | (0,0)      |  14.142135623731            | (-3,4)     | (10,10)    | 14.3178210632764
    | (10,10)    | (-3,4)     | 14.3178210632764            | (-5,-12)   | (-3,4)     | 16.1245154965971
 
--- 150,157 ----            | (-5,-12)   | (-10,0)    |               13            | (-5,-12)   | (0,0)      |
     13            | (0,0)      | (-5,-12)   |               13
 
!            | (0,0)      | (10,10)    | 14.1421356237309
!            | (10,10)    | (0,0)      | 14.1421356237309            | (-3,4)     | (10,10)    | 14.3178210632764
    | (10,10)    | (-3,4)     | 14.3178210632764            | (-5,-12)   | (-3,4)     | 16.1245154965971
 
***************
*** 221,227 ****          | (-10,0)    | (0,0)      |               10          | (-10,0)    | (-5,-12)   |
 13          | (-5,-12)   | (0,0)      |               13
 
!          | (0,0)      | (10,10)    |  14.142135623731          | (-3,4)     | (10,10)    | 14.3178210632764
|(-5,-12)   | (-3,4)     | 16.1245154965971          | (-10,0)    | (10,10)    | 22.3606797749979
 
--- 221,227 ----          | (-10,0)    | (0,0)      |               10          | (-10,0)    | (-5,-12)   |
 13          | (-5,-12)   | (0,0)      |               13
 
!          | (0,0)      | (10,10)    | 14.1421356237309          | (-3,4)     | (10,10)    | 14.3178210632764
|(-5,-12)   | (-3,4)     | 16.1245154965971          | (-10,0)    | (10,10)    | 22.3606797749979
 

======================================================================

*** /«PKGBUILDDIR»/build/../src/test/regress/expected/polygon.out    Mon Oct 24 20:08:51 2016
--- /«PKGBUILDDIR»/build/src/test/regress/results/polygon.out    Mon Jan 23 15:17:51 2017
***************
*** 222,229 ****     '(2,2)'::point <-> '((0,0),(1,4),(3,1))'::polygon as inside,     '(3,3)'::point <->
'((0,2),(2,0),(2,2))'::polygonas near_corner,     '(4,4)'::point <-> '((0,0),(0,3),(4,0))'::polygon as near_segment;
 
!  on_corner | on_segment | inside |   near_corner   | near_segment 
! -----------+------------+--------+-----------------+--------------
!          0 |          0 |      0 | 1.4142135623731 |          3.2 (1 row) 
--- 222,229 ----     '(2,2)'::point <-> '((0,0),(1,4),(3,1))'::polygon as inside,     '(3,3)'::point <->
'((0,2),(2,0),(2,2))'::polygonas near_corner,     '(4,4)'::point <-> '((0,0),(0,3),(4,0))'::polygon as near_segment;
 
!  on_corner | on_segment | inside |   near_corner    | near_segment 
! -----------+------------+--------+------------------+--------------
!          0 |          0 |      0 | 1.41421356237309 |          3.2 (1 row) 


The 9.4.11 log contains the same point.out diff, but not polygon.out:

https://buildd.debian.org/status/fetch.php?pkg=postgresql-9.4&arch=powerpc&ver=9.4.11-0%2Bdeb8u1&stamp=1487517299&raw=0

Does that ring any bell? As Debian unstable is unaffected, it's likely
the toolchain to be blamed, but it worked for Debian Jessie before.

Christoph
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