[IfConversion] Fix diamond conversion with unanalyzable branches.
The code was incorrectly counting the number of identical
instructions, and therefore tried to predicate an instruction which
should not have been predicated. This could have various effects: a
compiler crash, an assembler failure, a miscompile, or just
generating an extra, unnecessary instruction.
Instead of depending on TargetInstrInfo::removeBranch, which only
works on analyzable branches, just remove all branch instructions.
Fixes https://bugs.llvm.org/show_bug.cgi?id=43121 and
https://bugs.llvm.org/show_bug.cgi?id=41121 .
Differential Revision: https://reviews.llvm.org/D67203
This should fix "Unable to predicate BX killed renamable $r0" errors
when building the lang/spidermonkey170 and lang/spidermonkey38 ports for
armv7 and armv6.
PR: 236567
MFC after: 3 days
b7e6cfce0a