A register def can be partially dead when the whole register has use(s) but a subreg does not.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31760 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 730ad23..03f3860 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -575,7 +575,6 @@
// A physical register cannot be live across basic block, so its
// lifetime must end somewhere in its defining basic block.
DEBUG(std::cerr << "\t\tregister: "; printRegName(interval.reg));
- typedef LiveVariables::killed_iterator KillIter;
unsigned baseIndex = MIIdx;
unsigned start = getDefIndex(baseIndex);
@@ -599,6 +598,14 @@
DEBUG(std::cerr << " killed");
end = getUseIndex(baseIndex) + 1;
goto exit;
+ } else if (lv_->ModifiesRegister(mi, interval.reg)) {
+ // Another instruction redefines the register before it is ever read.
+ // Then the register is essentially dead at the instruction that defines
+ // it. Hence its interval is:
+ // [defSlot(def), defSlot(def)+1)
+ DEBUG(std::cerr << " dead");
+ end = getDefIndex(start) + 1;
+ goto exit;
}
}