[PATCH] D137958: [LAA] Use cross-iteration alias analysis

[Nikita Popov via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG4de3184f07fd: [LAA] Use cross-iteration alias analysis (authored by nikic).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D137958/new/

https://reviews.llvm.org/D137958

Files:
  llvm/include/llvm/Analysis/AliasAnalysis.h
  llvm/lib/Analysis/LoopAccessAnalysis.cpp
  llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll


Index: llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll
===================================================================
--- /dev/null
+++ llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll
@@ -0,0 +1,30 @@
+; RUN: opt -passes='print<access-info>' -disable-output 2>&1 < %s | FileCheck %s
+
+; CHECK: Dependences:
+; CHECK-NEXT: Unknown:
+; CHECK-NEXT: %t63 = load double, ptr %t62, align 8 ->
+; CHECK-NEXT: store double %t63, ptr %t64, align 8
+
+define i32 @test() {
+   %a1 = alloca [128 x double], align 8
+   %a2 = alloca [128 x double], align 8
+   %a3 = alloca [128 x double], align 8
+   %t30 = getelementptr double, ptr %a2, i64 -32
+   br label %loop
+
+loop:
+   %t58 = phi i64 [ %t65, %loop ], [ 0, %0 ]
+   %t59 = icmp ule i64 %t58, 32
+   %t60 = select i1 %t59, ptr %a1, ptr %t30
+   %t62 = getelementptr inbounds double, ptr %t60, i64 %t58
+   %t63 = load double, ptr %t62, align 8
+   %t61 = select i1 %t59, ptr %a2, ptr %a3
+   %t64 = getelementptr inbounds double, ptr %t61, i64 %t58
+   store double %t63, ptr %t64, align 8
+   %t65 = add nuw nsw i64 %t58, 1
+   %t66 = icmp eq i64 %t65, 94
+   br i1 %t66, label %exit, label %loop
+
+exit:
+   ret i32 0
+}
Index: llvm/lib/Analysis/LoopAccessAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -622,7 +622,10 @@
   AccessAnalysis(Loop *TheLoop, AAResults *AA, LoopInfo *LI,
                  MemoryDepChecker::DepCandidates &DA,
                  PredicatedScalarEvolution &PSE)
-      : TheLoop(TheLoop), BAA(*AA), AST(BAA), LI(LI), DepCands(DA), PSE(PSE) {}
+      : TheLoop(TheLoop), BAA(*AA), AST(BAA), LI(LI), DepCands(DA), PSE(PSE) {
+    // We're analyzing dependences across loop iterations.
+    BAA.enableCrossIterationMode();
+  }
 
   /// Register a load  and whether it is only read from.
   void addLoad(MemoryLocation &Loc, Type *AccessTy, bool IsReadOnly) {
Index: llvm/include/llvm/Analysis/AliasAnalysis.h
===================================================================
--- llvm/include/llvm/Analysis/AliasAnalysis.h
+++ llvm/include/llvm/Analysis/AliasAnalysis.h
@@ -651,6 +651,11 @@
                                 DominatorTree *DT) {
     return AA.callCapturesBefore(I, MemLoc, DT, AAQI);
   }
+
+  /// Assume that values may come from different cycle iterations.
+  void enableCrossIterationMode() {
+    AAQI.MayBeCrossIteration = true;
+  }
 };
 
 /// Temporary typedef for legacy code that uses a generic \c AliasAnalysis


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