commit 6d12331ad5a27e85429abf33d54d6576546fff60
author Nicolas Capens <capn@google.com> Mon Jan 08 12:57:52 2018 -0500
committer Nicolas Capens <nicolascapens@google.com> Tue Jan 09 16:18:12 2018 +0000
tree 1f10c5109d090e1f2343dadeed0f9e250049d8b8
parent d6bcc11172ba569e22147c09e650b840eb7ab76d

Fix break statement.

The break 'depth' was used to indicate the number of if/else execution
enable mask's stack levels we need to discard when jumping from a break
statement to its enclosing switch or loop. However, each switch and
loop resets this depth at the end, which isn't correct for nested loops
and/or switches (note that switches contain if/else statements, and
loops use the same 'enable' masks as if/else).

This can be fixed either by using a stack to keep track of the break
depths of nested switch/loop statements, or by simply not jumping
directly from the break statement to the end of it's enclosing switch
or loop. The latter fix was chosen for this change, which assumes that
that it's uncommon for all vector lanes to become disabled at the break
statement and skip many instructions. An important exception to this is
breaking out of an infinite or long-running loop, but this is handled
by checking the break enable mask as part of the loop condition.

Change-Id: I57d2e03941e855faefd997442931ff8619eca73f
Reviewed-on: https://swiftshader-review.googlesource.com/15968
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>