Fix a bug in IfConverter with nested predicates.
Prior to this patch, IfConverter may widen the cases where a sequence of
instructions were executed because of the way it uses nested predicates. This
result in incorrect execution.
For instance, Let A be a basic block that flows conditionally into B and B be a
predicated block.
B can be predicated with A.BrToBPredicate into A iff B.Predicate is less
"permissive" than A.BrToBPredicate, i.e., iff A.BrToBPredicate subsumes
B.Predicate.
The IfConverter was checking the opposite: B.Predicate subsumes
A.BrToBPredicate.
<rdar://problem/14379453>
llvm-svn: 187071
diff --git a/llvm/lib/CodeGen/IfConversion.cpp b/llvm/lib/CodeGen/IfConversion.cpp
index f4485d5..1ae7e3b 100644
--- a/llvm/lib/CodeGen/IfConversion.cpp
+++ b/llvm/lib/CodeGen/IfConversion.cpp
@@ -720,9 +720,9 @@
if (BBI.IsDone || BBI.IsUnpredicable)
return false;
- // If it is already predicated, check if its predicate subsumes the new
- // predicate.
- if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Pred))
+ // If it is already predicated, check if the new predicate subsumes
+ // its predicate.
+ if (BBI.Predicate.size() && !TII->SubsumesPredicate(Pred, BBI.Predicate))
return false;
if (BBI.BrCond.size()) {