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The common code in the post-RA scheduler to break anti-dependencies on the critical path contained a flaw. In the reported case, an anti-dependency between the overlapping registers %X4 and %R4 exists: %X29<def> = OR8 %X4, %X4 %R4<def>, %X3<def,dead,tied3> = LBZU 1, %X3<kill,tied1> The unpatched code breaks the dependency by replacing %R4 and its uses with %R3, the first register on the available list. However, %R3 and %X3 overlap, so this creates two overlapping definitions on the same instruction. The fix is straightforward, preventing selection of a register that overlaps any other defined register on the same instruction. The test case is reduced from the bug report, and verifies that we no longer produce "lbzu 3, 1(3)" when breaking this anti-dependency. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173706 91177308-0d34-0410-b5e6-96231b3b80d8
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