[EarlyIfConversion] Don't if-convert unconditional branches.
A block ending in an unconditional branch can have two successors if one
is a landing pad. In practice, I think this only has an effect on
Windows because landing pads are never empty for Itanium unwinding.
(Alternatively, I could add a check to
AArch64InstrInfo::canInsertSelect, but this seems more obvious.)
Differential Revision: https://reviews.llvm.org/D56468
llvm-svn: 351142
diff --git a/llvm/lib/CodeGen/EarlyIfConversion.cpp b/llvm/lib/CodeGen/EarlyIfConversion.cpp
index 098afd8..364e1f0 100644
--- a/llvm/lib/CodeGen/EarlyIfConversion.cpp
+++ b/llvm/lib/CodeGen/EarlyIfConversion.cpp
@@ -398,6 +398,13 @@
return false;
}
+ // Make sure the analyzed branch is conditional; one of the successors
+ // could be a landing pad. (Empty landing pads can be generated on Windows.)
+ if (Cond.empty()) {
+ LLVM_DEBUG(dbgs() << "AnalyzeBranch found an unconditional branch.\n");
+ return false;
+ }
+
// AnalyzeBranch doesn't set FBB on a fall-through branch.
// Make sure it is always set.
FBB = TBB == Succ0 ? Succ1 : Succ0;