Add text explaining an assertion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122617 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/StrongPHIElimination.cpp b/lib/CodeGen/StrongPHIElimination.cpp
index 5713e6aed29531248e27971eb9c742c74518d14f..4749d8eca8865f20689018585f7d6ae9a75a7f27 100644 (file)
--- a/lib/CodeGen/StrongPHIElimination.cpp
+++ b/lib/CodeGen/StrongPHIElimination.cpp
@@ -283,7 +283,9 @@ bool StrongPHIElimination::runOnMachineFunction(MachineFunction& MF) {
     LiveInterval& DestLI = LI->getInterval(DestReg);
     LiveInterval& NewLI = LI->getInterval(NewReg);
 
-    assert(DestLI.ranges.size() == 1);
+    assert(DestLI.ranges.size() == 1
+           && "PHI destination copy's live interval should be a single live "
+               "range from the beginning of the BB to the copy instruction.");
     LiveRange* DestLR = DestLI.begin();
     VNInfo* NewVNI = NewLI.getVNInfoAt(DestLR->start);
     if (!NewVNI) {