[polly] r245294 - Fix Codegen adding a second exit out of region

[Michael Kruse via llvm-commits]

Author: meinersbur
Date: Tue Aug 18 08:14:42 2015
New Revision: 245294

URL: http://llvm.org/viewvc/llvm-project?rev=245294&view=rev
Log:
Fix Codegen adding a second exit out of region

executeScopConditionally would destroy a predecessor region if it the
scop's entry was the region's exit block by forking it to polly.start
and thus creating a secnd exit out of the region. This patch "shrinks"
the predecessor region s.t. polly.split_new_and_old is not the 
region's exit anymore. 


Added:
    polly/trunk/test/Isl/CodeGen/split_edge_of_exit.ll
Modified:
    polly/trunk/lib/CodeGen/Utils.cpp

Modified: polly/trunk/lib/CodeGen/Utils.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/CodeGen/Utils.cpp?rev=245294&r1=245293&r2=245294&view=diff
==============================================================================
--- polly/trunk/lib/CodeGen/Utils.cpp (original)
+++ polly/trunk/lib/CodeGen/Utils.cpp Tue Aug 18 08:14:42 2015
@@ -103,6 +103,18 @@ BasicBlock *polly::executeScopConditiona
       splitEdge(EnteringBB, EntryBB, ".split_new_and_old", &DT, &LI, &RI);
   SplitBlock->setName("polly.split_new_and_old");
 
+  // If EntryBB is the exit block of the region that includes Prev, exclude
+  // SplitBlock from that region by making it itself the exit block. This is
+  // trivially possible because there is just one edge to EnteringBB.
+  // This is necessary because we will add an outgoing edge from SplitBlock,
+  // which would violate the single exit block requirement of PrevRegion.
+  Region *PrevRegion = RI.getRegionFor(EnteringBB);
+  while (PrevRegion->getExit() == EntryBB) {
+    PrevRegion->replaceExit(SplitBlock);
+    PrevRegion = PrevRegion->getParent();
+  }
+  RI.setRegionFor(SplitBlock, PrevRegion);
+
   // Create a join block
   BasicBlock *ExitingBB = R.getExitingBlock();
   BasicBlock *ExitBB = R.getExit();

Added: polly/trunk/test/Isl/CodeGen/split_edge_of_exit.ll
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/Isl/CodeGen/split_edge_of_exit.ll?rev=245294&view=auto
==============================================================================
--- polly/trunk/test/Isl/CodeGen/split_edge_of_exit.ll (added)
+++ polly/trunk/test/Isl/CodeGen/split_edge_of_exit.ll Tue Aug 18 08:14:42 2015
@@ -0,0 +1,31 @@
+; RUN: opt %loadPolly -polly-detect-unprofitable -polly-no-early-exit -polly-detect -analyze < %s | FileCheck %s
+; RUN: opt %loadPolly -polly-detect-unprofitable -polly-no-early-exit -polly-codegen -verify-region-info -analyze < %s
+;
+; This is a scop directly precedented by a region, i.e. the scop's entry is the
+; region's exit block. This test is to ensure that the RegionInfo is correctly
+; preserved.
+;
+; CHECK: Valid Region for Scop: region2 => return
+;
+define void @f1(i64* %A, i64 %N) nounwind {
+entry:
+  br label %region1
+
+region1:
+  %indvar1 = phi i64 [ 0, %entry ], [ %indvar1.next, %region1 ]
+  fence seq_cst
+  %indvar1.next = add nsw i64 %indvar1, 1
+  %exitcond1 = icmp eq i64 %indvar1.next, %N
+  br i1 %exitcond1, label %region2, label %region1
+
+region2:
+  %indvar2 = phi i64 [ 0, %region1 ], [ %indvar2.next, %region2 ]
+  %scevgep2 = getelementptr i64, i64* %A, i64 %indvar2
+  store i64 %indvar2, i64* %scevgep2
+  %indvar2.next = add nsw i64 %indvar2, 1
+  %exitcond2 = icmp eq i64 %indvar2.next, %N
+  br i1 %exitcond2, label %return, label %region2
+
+return:
+  ret void
+}