Do not consider subreg defs as reads when computing subrange liveness
Subregister definitions are considered uses for the purpose of tracking
liveness of the whole register. At the same time, when calculating live
interval subranges, subregister defs should not be treated as uses.
Differential Revision: https://reviews.llvm.org/D24190
llvm-svn: 280532
diff --git a/llvm/lib/CodeGen/LiveRangeCalc.h b/llvm/lib/CodeGen/LiveRangeCalc.h
index 84cc1cb..892f535 100644
--- a/llvm/lib/CodeGen/LiveRangeCalc.h
+++ b/llvm/lib/CodeGen/LiveRangeCalc.h
@@ -160,6 +160,7 @@
/// all uses must be jointly dominated by the definitions from @p LR
/// together with definitions of other lanes where @p LR becomes undefined
/// (via <def,read-undef> operands).
+ /// If @p LR is a main range, the @p LaneMask should be set to ~0.
void extendToUses(LiveRange &LR, unsigned Reg, LaneBitmask LaneMask,
LiveInterval *LI = nullptr);