[IRBuilder] Only emit alias scop metadata for arrays, but not scalars

tobiasgrosser · tobiasgrosser · commit 4a07bbe3f67c · 2017-08-22T21:58:48.000Z
Summary: There is no need to emit alias metadata for scalars, as basicaa will easily distinguish them from arrays. This reduces the size of the metadata we generate. This is especially useful after we moved to -polly-position=before-vectorizer, where a lot more scalar dependences are introduced, which increased the size of the alias analysis metadata and made us commonly reach the limits after which we do not emit alias metadata that have been introduced to prevent quadratic growth of this alias metadata. This improves 2mm performance from 1.5 seconds to 0.17 seconds. Reviewers: Meinersbur, bollu, singam-sanjay Reviewed By: Meinersbur Subscribers: pollydev, llvm-commits Tags: #polly Differential Revision: https://reviews.llvm.org/D37028 llvm-svn: 311498
diff --git a/polly/lib/CodeGen/IRBuilder.cpp b/polly/lib/CodeGen/IRBuilder.cpp
@@ -15,6 +15,7 @@
 #include "polly/CodeGen/IRBuilder.h"
 #include "polly/ScopInfo.h"
 #include "polly/Support/ScopHelper.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/Support/Debug.h"
 
@@ -60,21 +61,28 @@ void ScopAnnotator::buildAliasScopes(Scop &S) {
   AliasScopeMap.clear();
   OtherAliasScopeListMap.clear();
 
+  // We are only interested in arrays, but no scalar references. Scalars should
+  // be handled easily by basicaa.
+  SmallVector<ScopArrayInfo *, 10> Arrays;
+  for (ScopArrayInfo *Array : S.arrays())
+    if (Array->isArrayKind())
+      Arrays.push_back(Array);
+
   // The construction of alias scopes is quadratic in the number of arrays
   // involved. In case of too many arrays, skip the construction of alias
   // information to avoid quadratic increases in compile time and code size.
-  if (std::distance(S.array_begin(), S.array_end()) > MaxArraysInAliasScops)
+  if (Arrays.size() > MaxArraysInAliasScops)
     return;
 
   std::string AliasScopeStr = "polly.alias.scope.";
-  for (const ScopArrayInfo *Array : S.arrays()) {
+  for (const ScopArrayInfo *Array : Arrays) {
     assert(Array->getBasePtr() && "Base pointer must be present");
     AliasScopeMap[Array->getBasePtr()] =
         getID(Ctx, AliasScopeDomain,
               MDString::get(Ctx, (AliasScopeStr + Array->getName()).c_str()));
   }
 
-  for (const ScopArrayInfo *Array : S.arrays()) {
+  for (const ScopArrayInfo *Array : Arrays) {
     MDNode *AliasScopeList = MDNode::get(Ctx, {});
     for (const auto &AliasScopePair : AliasScopeMap) {
       if (Array->getBasePtr() == AliasScopePair.first)
diff --git a/polly/test/Isl/CodeGen/MemAccess/create_arrays.ll b/polly/test/Isl/CodeGen/MemAccess/create_arrays.ll
@@ -32,15 +32,14 @@
 ; CODEGEN:  {{%.*}} = load double, double* %polly.access.E, align 8, !alias.scope [[TAG0:![0-9]+]], !noalias [[TAG2:![0-9]+]]
 ; CODEGEN:  store double {{%.*}}, double* %scevgep36, align 8, !alias.scope [[TAG5:![0-9]+]], !noalias [[TAG8:![0-9]+]]
 ;
-; CODEGEN-DAG: [[TAG0]] = distinct !{[[TAG0]], [[TAG1:![0-9]+]], !"polly.alias.scope.E"}
-; CODEGEN-DAG: [[TAG1]] = distinct !{[[TAG1]], !"polly.alias.scope.domain"}
-; CODEGEN-DAG: [[TAG2]] = !{[[TAG3:![0-9]+]], [[TAG4:![0-9]+]], [[TAG5:![0-9]+]], [[TAG6:![0-9]+]], [[TAG7:![0-9]+]]}
-; CODEGEN-DAG: [[TAG3]] = distinct !{[[TAG3]], [[TAG1]], !"polly.alias.scope.MemRef_B"}
-; CODEGEN-DAG: [[TAG4]] = distinct !{[[TAG4]], [[TAG1]], !"polly.alias.scope.MemRef_beta"}
-; CODEGEN-DAG: [[TAG5]] = distinct !{[[TAG5]], [[TAG1]], !"polly.alias.scope.MemRef_A"}
-; CODEGEN-DAG: [[TAG6]] = distinct !{[[TAG6]], [[TAG1]], !"polly.alias.scope.D"}
-; CODEGEN-DAG: [[TAG7]] = distinct !{[[TAG7]], [[TAG1]], !"polly.alias.scope.F"}
-; CODEGEN-DAG: [[TAG8]] = !{[[TAG3]], [[TAG4]], [[TAG6]], [[TAG0]], [[TAG7]]}
+; CODEGEN: [[TAG0]] = distinct !{[[TAG0]], [[TAG1:![0-9]+]], !"polly.alias.scope.E"}
+; CODEGEN: [[TAG1]] = distinct !{[[TAG1]], !"polly.alias.scope.domain"}
+; CODEGEN: [[TAG2]] = !{[[TAG3:![0-9]+]], [[TAG4:![0-9]+]], [[TAG5:![0-9]+]], [[TAG6:![0-9]+]]}
+; CODEGEN: [[TAG3]] = distinct !{[[TAG3]], [[TAG1]], !"polly.alias.scope.MemRef_B"}
+; CODEGEN: [[TAG4]] = distinct !{[[TAG4]], [[TAG1]], !"polly.alias.scope.MemRef_A"}
+; CODEGEN: [[TAG5]] = distinct !{[[TAG5]], [[TAG1]], !"polly.alias.scope.D"}
+; CODEGEN: [[TAG6]] = distinct !{[[TAG6]], [[TAG1]], !"polly.alias.scope.F"}
+; CODEGEN: [[TAG7:![0-9]+]] = !{[[TAG3]], [[TAG5]], [[TAG0]], [[TAG6]]}
 ;
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-unknown"
diff --git a/polly/test/ScheduleOptimizer/pattern-matching-based-opts_10.ll b/polly/test/ScheduleOptimizer/pattern-matching-based-opts_10.ll
@@ -12,13 +12,13 @@
 ; This test case checks whether Polly generates second level alias metadata
 ; to distinguish the specific accesses in case of the ublas gemm kernel.
 ;
-; CHECK: !13 = distinct !{!13, !0, !"second level alias metadata"}
+; CHECK: !11 = distinct !{!11, !0, !"second level alias metadata"}
+; CHECK: !12 = distinct !{!12, !0, !"second level alias metadata"}
+; CHECK: !13 = !{!3, !4, !5, !6, !11}
 ; CHECK: !14 = distinct !{!14, !0, !"second level alias metadata"}
-; CHECK: !15 = !{!3, !4, !5, !6, !7, !8, !13}
+; CHECK: !15 = !{!3, !4, !5, !6, !11, !12}
 ; CHECK: !16 = distinct !{!16, !0, !"second level alias metadata"}
-; CHECK: !17 = !{!3, !4, !5, !6, !7, !8, !13, !14}
-; CHECK: !18 = distinct !{!18, !0, !"second level alias metadata"}
-; CHECK: !19 = !{!3, !4, !5, !6, !7, !8, !13, !14, !16}
+; CHECK: !17 = !{!3, !4, !5, !6, !11, !12, !14}
 ;
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-unknown"
