[Polly CodeGen] Break critical edge from RTC to original loop.

This makes polly generate a CFG which is closer to what we want
in LLVM IR, with a loop preheader for the original loop. This is
just a cleanup, but it exposes some fragile assumptions.

I'm not completely happy with the changes related to expandCodeFor;
RTCBB->getTerminator() is basically a random insertion point which
happens to work due to the way we generate runtime checks. I'm not
sure what the right answer looks like, though.

Differential Revision: https://reviews.llvm.org/D26053

llvm-svn: 285864

1 files changed, 3 insertions, 2 deletions

diff --git a/polly/lib/CodeGen/CodeGeneration.cpp b/polly/lib/CodeGen/CodeGeneration.cpp
index 68b1d830e47..9fcd6dfba37 100644
--- a/polly/lib/CodeGen/CodeGeneration.cpp
+++ b/polly/lib/CodeGen/CodeGeneration.cpp
@@ -133,8 +133,6 @@ public:
     assert(EnteringBB);
     PollyIRBuilder Builder = createPollyIRBuilder(EnteringBB, Annotator);
 
-    IslNodeBuilder NodeBuilder(Builder, Annotator, this, *DL, *LI, *SE, *DT, S);
-
     // Only build the run-time condition and parameters _after_ having
     // introduced the conditional branch. This is important as the conditional
     // branch will guard the original scop from new induction variables that
@@ -145,6 +143,9 @@ public:
         executeScopConditionally(S, this, Builder.getTrue());
     auto *SplitBlock = StartBlock->getSinglePredecessor();
 
+    IslNodeBuilder NodeBuilder(Builder, Annotator, this, *DL, *LI, *SE, *DT, S,
+                               StartBlock);
+
     // First generate code for the hoisted invariant loads and transitively the
     // parameters they reference. Afterwards, for the remaining parameters that
     // might reference the hoisted loads. Finally, build the runtime check