[committed 0/4] MIPS/BFD: LA25 stub generation fixes

[Maciej W. Rozycki]

Hi,

 A recent change to the MIPS/ELF BFD linker backend, commit 9d862524f6ae 
("MIPS: Verify the ISA mode and alignment of branch and jump targets") has 
caused a build regression in microMIPS glibc where the `zdump' tool fails 
to link:

.../timezone/zdump.o: In function `yeartot':
.../timezone/zdump.c:758:(.text+0x62): Jump to a non-instruction-aligned address
.../timezone/zdump.c:758:(.text+0x76): Jump to a non-instruction-aligned address
.../timezone/zdump.c:768:(.text+0x112): Jump to a non-instruction-aligned address
.../timezone/zdump.c:774:(.text+0x1b8): Jump to a non-instruction-aligned address
.../timezone/zdump.c:774:(.text+0x1cc): Jump to a non-instruction-aligned address
collect2: error: ld returned 1 exit status
make[2]: *** [.../timezone/zdump] Error 1

This has been reported by Faraz and has been missed in the development of 
the commit referred as we lack a test case for LA25 stub generation in 
microMIPS code.  

 I have therefore adapted one of the existing test cases aimed at LA25 
stubs in regular MIPS code.  That test case triggered further 3 bugs, of 
which 2 -- for the total of 3 -- are addressed in this small patch series.  
The test case then follows as a separate 4th patch only as otherwise it 
would initially have to fail, or alternatively accept incorrect output and 
then get adjusted with each of the following fixes.

 The 4th bug seems very complex to fix and is a missed optimisation rather 
than a correctness issue, and then for a corner case only.  I have 
therefore decided not to address it at this time and filed PR ld/20453 
instead, recording a KFAIL in the test suite.

 See individual patch descriptions for the details of the problems 
addressed.

  Maciej