[polly] r311403 - [DeLICM] Fix unused zone for writes without in-between read.

[Michael Kruse via llvm-commits]

Author: meinersbur
Date: Mon Aug 21 16:04:45 2017
New Revision: 311403

URL: http://llvm.org/viewvc/llvm-project?rev=311403&view=rev
Log:
[DeLICM] Fix unused zone for writes without in-between read.

The implementation of computeArrayUnused did not consider writes without
reads before, except for the first write in the SCoP. This caused it to
'forget' writes directly following another write.

This patch re-adds the entire reaching defintion of a write that has not
been covered before by a read.

This fixes Polybench 4.2 2mm where only one of the matrix-multiplication
was detected.

Modified:
    polly/trunk/lib/Support/ISLTools.cpp
    polly/trunk/unittests/Isl/IslTest.cpp

Modified: polly/trunk/lib/Support/ISLTools.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/Support/ISLTools.cpp?rev=311403&r1=311402&r2=311403&view=diff
==============================================================================
--- polly/trunk/lib/Support/ISLTools.cpp (original)
+++ polly/trunk/lib/Support/ISLTools.cpp Mon Aug 21 16:04:45 2017
@@ -366,13 +366,6 @@ polly::computeArrayUnused(isl::union_map
   auto WriteActions =
       give(isl_union_map_apply_domain(Schedule.copy(), Writes.copy()));
 
-  // { [Element[] -> Scatter[] }
-  auto AfterReads = afterScatter(ReadActions, ReadEltInSameInst);
-  auto WritesBeforeAnyReads =
-      give(isl_union_map_subtract(WriteActions.take(), AfterReads.take()));
-  auto BeforeWritesBeforeAnyReads =
-      beforeScatter(WritesBeforeAnyReads, !IncludeWrite);
-
   // { [Element[] -> DomainWrite[]] -> Scatter[] }
   auto EltDomWrites = give(isl_union_map_apply_range(
       isl_union_map_range_map(isl_union_map_reverse(Writes.copy())),
@@ -390,15 +383,26 @@ polly::computeArrayUnused(isl::union_map
   auto ReadsOverwrittenRotated = give(isl_union_map_reverse(
       isl_union_map_curry(reverseDomain(ReadsOverwritten).take())));
   auto LastOverwrittenRead =
-      give(isl_union_map_lexmax(ReadsOverwrittenRotated.take()));
+      give(isl_union_map_lexmax(ReadsOverwrittenRotated.copy()));
 
   // { [Element[] -> DomainWrite[]] -> Scatter[] }
   auto BetweenLastReadOverwrite = betweenScatter(
       LastOverwrittenRead, EltDomWrites, IncludeLastRead, IncludeWrite);
 
-  return give(isl_union_map_union(
-      BeforeWritesBeforeAnyReads.take(),
-      isl_union_map_domain_factor_domain(BetweenLastReadOverwrite.take())));
+  // { [Element[] -> Scatter[]] -> DomainWrite[] }
+  isl::union_map ReachingOverwriteZone = computeReachingWrite(
+      Schedule, Writes, true, IncludeLastRead, IncludeWrite);
+
+  // { [Element[] -> DomainWrite[]] -> Scatter[] }
+  isl::union_map ReachingOverwriteRotated =
+      reverseDomain(ReachingOverwriteZone).curry().reverse();
+
+  // { [Element[] -> DomainWrite[]] -> Scatter[] }
+  isl::union_map WritesWithoutReads = ReachingOverwriteRotated.subtract_domain(
+      ReadsOverwrittenRotated.domain());
+
+  return BetweenLastReadOverwrite.unite(WritesWithoutReads)
+      .domain_factor_domain();
 }
 
 isl::union_set polly::convertZoneToTimepoints(isl::union_set Zone,

Modified: polly/trunk/unittests/Isl/IslTest.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/unittests/Isl/IslTest.cpp?rev=311403&r1=311402&r2=311403&view=diff
==============================================================================
--- polly/trunk/unittests/Isl/IslTest.cpp (original)
+++ polly/trunk/unittests/Isl/IslTest.cpp Mon Aug 21 16:04:45 2017
@@ -783,6 +783,14 @@ TEST(DeLICM, computeArrayUnused) {
               computeArrayUnused(UMAP("{ Write[] -> [0] }"),
                                  UMAP("{ Write[] -> Elt[] }"), UMAP("{}"),
                                  ReadEltInSameInst, false, true));
+
+    // read, write, write
+    EXPECT_EQ(
+        UMAP("{ Elt[] -> [i] : 0 < i <= 20 }"),
+        computeArrayUnused(
+            UMAP("{ Read[] -> [0]; WriteA[] -> [10];  WriteB[] -> [20] }"),
+            UMAP("{ WriteA[] -> Elt[]; WriteB[] -> Elt[] }"),
+            UMAP("{ Read[] -> Elt[] }"), ReadEltInSameInst, false, true));
   }
 
   // Read and write in same statement