From 28e3e89764c2d6194feb3afba756f33a596cfc07 Mon Sep 17 00:00:00 2001
From: Tobias Grosser <tobias@grosser.es>
Date: Sun, 25 Oct 2015 22:55:59 +0000
Subject: [PATCH] RegionInfo: Correctly expand regions

Instead of playing around with dominance to verify if the possible expansion of
a scop region is indeed a single entry single exit region, we now distinguish
two cases. In case we only append a basic block, all edges entering this basic
block need to have come from within the region that is expanded. In case we join
two regions, the source basic blocks of the edges that end at the entry node of
the region that is appended most be part of either the original region or the
region that is appended.

This change will be tested through Polly.

This fixes llvm.org/PR25242

llvm-svn: 251267
---
 llvm/include/llvm/Analysis/RegionInfoImpl.h | 24 +++++++++------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/llvm/include/llvm/Analysis/RegionInfoImpl.h b/llvm/include/llvm/Analysis/RegionInfoImpl.h
index 0598068d69d3..134cd8f96fbe 100644
--- a/llvm/include/llvm/Analysis/RegionInfoImpl.h
+++ b/llvm/include/llvm/Analysis/RegionInfoImpl.h
@@ -444,16 +444,14 @@ typename Tr::RegionT *RegionBase<Tr>::getExpandedRegion() const {
   if (NumSuccessors == 0)
     return nullptr;
 
-  for (PredIterTy PI = InvBlockTraits::child_begin(getExit()),
-                  PE = InvBlockTraits::child_end(getExit());
-       PI != PE; ++PI) {
-    if (!DT->dominates(getEntry(), *PI))
-      return nullptr;
-  }
-
   RegionT *R = RI->getRegionFor(exit);
 
   if (R->getEntry() != exit) {
+    for (PredIterTy PI = InvBlockTraits::child_begin(getExit()),
+                    PE = InvBlockTraits::child_end(getExit());
+         PI != PE; ++PI)
+      if (!contains(*PI))
+        return nullptr;
     if (Tr::getNumSuccessors(exit) == 1)
       return new RegionT(getEntry(), *BlockTraits::child_begin(exit), RI, DT);
     return nullptr;
@@ -462,13 +460,11 @@ typename Tr::RegionT *RegionBase<Tr>::getExpandedRegion() const {
   while (R->getParent() && R->getParent()->getEntry() == exit)
     R = R->getParent();
 
-  if (!DT->dominates(getEntry(), R->getExit())) {
-    for (PredIterTy PI = InvBlockTraits::child_begin(getExit()),
-                    PE = InvBlockTraits::child_end(getExit());
-         PI != PE; ++PI) {
-      if (!DT->dominates(R->getExit(), *PI))
-        return nullptr;
-    }
+  for (PredIterTy PI = InvBlockTraits::child_begin(getExit()),
+                  PE = InvBlockTraits::child_end(getExit());
+       PI != PE; ++PI) {
+    if (!(contains(*PI) || R->contains(*PI)))
+      return nullptr;
   }
 
   return new RegionT(getEntry(), R->getExit(), RI, DT);