Update comments.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124843 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TailDuplication.cpp b/lib/CodeGen/TailDuplication.cpp
index 83706de..04d3d31 100644
--- a/lib/CodeGen/TailDuplication.cpp
+++ b/lib/CodeGen/TailDuplication.cpp
@@ -504,8 +504,9 @@
if (!I->isPHI() && !I->isDebugValue())
InstrCount += 1;
}
- // Heuristically, don't tail-duplicate calls if it would expand code size,
- // as it's less likely to be worth the extra cost.
+ // Don't tail-duplicate calls before register allocation. Calls presents a
+ // barrier to register allocation so duplicating them may end up increasing
+ // spills.
if (InstrCount > 1 && (PreRegAlloc && HasCall))
return false;