[Bug tree-optimization/78433] [7 Regression] glibc posix/execvpe.c gets miscompiled with -O3

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78433

--- Comment #2 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
On pcc64le this is the assembly diff:

--- good        2016-11-20 12:43:40.318860969 +0000
+++ bad 2016-11-20 12:42:57.277928999 +0000
@@ -178,7 +178,7 @@
        sldi 9,9,3
        ld 10,0(1)
        mr 26,1
-       addi 9,9,38
+       addi 9,9,31
        addis 25,2,.LC2@toc@ha
        rldicr 9,9,0,59
        addi 25,25,.LC2@toc@l
@@ -286,7 +286,7 @@
        sldi 9,9,3
        ld 10,0(1)
        mr 23,1
-       addi 9,9,38
+       addi 9,9,31
        cmpdi 7,5,1
        rldicr 9,9,0,59
        neg 9,9