Subzero: Fix a bug in advanced phi lowering.
When a temporary is introduced to break a cycle, we neglected to update the predecessor count for one of the operands, leading to a possible assertion failure.
This problem isn't currently seen in master, but it arises when we enable register aliases, as in https://codereview.chromium.org/1427973003/ . No changes are seen in spec2k code generation as a result of this fix.
A consistency check is added to help find future problems like this.
Also, refactored iteration over the Phi descriptor array to use range-based for loops and avoid directly indexing the array.
BUG= none
R=jpp@chromium.org
Review URL: https://codereview.chromium.org/1435543002 .
1 file changed