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The aggressive anti-dependency breaker scans instructions, bottom-up, within the scheduling region in order to find opportunities where register renaming can be used to break anti-dependencies. Unfortunately, the aggressive anti-dep breaker was treating a register definition as defining all of that register's aliases (including super registers). This behavior is incorrect when the super register is live and there are other definitions of subregisters of the super register. For example, given the following sequence: %CR2EQ<def> = CROR %CR3UN, %CR3UN<kill> %CR2GT<def> = IMPLICIT_DEF %X4<def> = MFOCRF8 %CR2 the analysis of the first subregister definition would work as expected: Anti: %CR2GT<def> = IMPLICIT_DEF Def Groups: CR2GT=g194->g0(via CR2) Antidep reg: CR2GT (zero group) Use Groups: but the analysis of the second one would not: Anti: %CR2EQ<def> = CROR %CR3UN, %CR3UN<kill> Def Groups: CR2EQ=g195 Antidep reg: CR2EQ Rename Candidates for Group g195: ... because, when processing the %CR2GT<def>, we'd mark all super registers of %CR2GT (%CR2 in this case) as defined. As a result, when processing %CR2EQ<def>, %CR2 no longer appears to be live, and %CR2EQ<def>'s group is not %unioned with the %CR2 group. I don't have an in-tree test case for this yet (and even if I did, I don't have a small one). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202294 91177308-0d34-0410-b5e6-96231b3b80d8 |
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