Reapply r142781 with fix. Original message:

  Enhance SCEV's brute force loop analysis to handle multiple PHI nodes in the
  loop header when computing the trip count.

  With this, we now constant evaluate:
    struct ListNode { const struct ListNode *next; int i; };
    static const struct ListNode node1 = {0, 1};
    static const struct ListNode node2 = {&node1, 2};
    static const struct ListNode node3 = {&node2, 3};
    int test() {
      int sum = 0;
      for (const struct ListNode *n = &node3; n != 0; n = n->next)
        sum += n->i;
      return sum;
    }

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142790 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 1e4bf19e84971736228e8c53b2278ff682a86d47..1ab6a406fce04f2cc245b0b3849c944c572e1dc6 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -4882,29 +4882,33 @@ const SCEV *ScalarEvolution::ComputeExitCountExhaustively(const Loop *L,
   // That's the only form we support here.
   if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
 
+  DenseMap<Instruction *, Constant *> CurrentIterVals;
+  BasicBlock *Header = L->getHeader();
+  assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
+
   // One entry must be a constant (coming in from outside of the loop), and the
   // second must be derived from the same PHI.
   bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
-  Constant *StartCST =
-    dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
-  if (StartCST == 0) return getCouldNotCompute();  // Must be a constant.
-
-  Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
-  if (getConstantEvolvingPHI(BEValue, L) != PN &&
-      !isa<Constant>(BEValue))
-    return getCouldNotCompute();  // Not derived from same PHI.
+  PHINode *PHI = 0;
+  for (BasicBlock::iterator I = Header->begin();
+       (PHI = dyn_cast<PHINode>(I)); ++I) {
+    Constant *StartCST =
+      dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
+    if (StartCST == 0) continue;
+    CurrentIterVals[PHI] = StartCST;
+  }
+  if (!CurrentIterVals.count(PN))
+    return getCouldNotCompute();
 
   // Okay, we find a PHI node that defines the trip count of this loop.  Execute
   // the loop symbolically to determine when the condition gets a value of
   // "ExitWhen".
-  unsigned IterationNum = 0;
-  unsigned MaxIterations = MaxBruteForceIterations;   // Limit analysis.
-  for (Constant *PHIVal = StartCST;
-       IterationNum != MaxIterations; ++IterationNum) {
-    DenseMap<Instruction *, Constant *> PHIValMap;
-    PHIValMap[PN] = PHIVal;
+
+  unsigned MaxIterations = MaxBruteForceIterations;   // Limit analysis.  
+  for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
     ConstantInt *CondVal =
-      dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, L, PHIValMap, TD));
+      dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, L,
+                                                       CurrentIterVals, TD));
 
     // Couldn't symbolically evaluate.
     if (!CondVal) return getCouldNotCompute();
@@ -4914,11 +4918,19 @@ const SCEV *ScalarEvolution::ComputeExitCountExhaustively(const Loop *L,
       return getConstant(Type::getInt32Ty(getContext()), IterationNum);
     }
 
-    // Compute the value of the PHI node for the next iteration.
-    Constant *NextPHI = EvaluateExpression(BEValue, L, PHIValMap, TD);
-    if (NextPHI == 0 || NextPHI == PHIVal)
-      return getCouldNotCompute();// Couldn't evaluate or not making progress...
-    PHIVal = NextPHI;
+    // Update all the PHI nodes for the next iteration.
+    DenseMap<Instruction *, Constant *> NextIterVals;
+    for (DenseMap<Instruction *, Constant *>::const_iterator
+           I = CurrentIterVals.begin(), E = CurrentIterVals.end(); I != E; ++I){
+      PHINode *PHI = dyn_cast<PHINode>(I->first);
+      if (!PHI || PHI->getParent() != Header) continue;
+      Constant *&NextPHI = NextIterVals[PHI];
+      if (NextPHI) continue;    // Already computed!
+
+      Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
+      NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
+    }
+    CurrentIterVals.swap(NextIterVals);
   }
 
   // Too many iterations were needed to evaluate.

diff --git a/test/Analysis/ScalarEvolution/load.ll b/test/Analysis/ScalarEvolution/load.ll
index 203515285be27b25d40a107a0d43a883c0d98f19..2ff86e9d3cadbc564852cbb2a9c8c26175cac496 100644 (file)
--- a/test/Analysis/ScalarEvolution/load.ll
+++ b/test/Analysis/ScalarEvolution/load.ll
@@ -1,5 +1,4 @@
 ; RUN: opt -analyze -scalar-evolution < %s 2>&1 | FileCheck %s
-; PR11034
 
 target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
 target triple = "i386-pc-linux-gnu"
@@ -7,6 +6,7 @@ target triple = "i386-pc-linux-gnu"
 @arr1 = internal unnamed_addr constant [50 x i32] [i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 16, i32 17, i32 18, i32 19, i32 20, i32 21, i32 22, i32 23, i32 24, i32 25, i32 26, i32 27, i32 28, i32 29, i32 30, i32 31, i32 32, i32 33, i32 34, i32 35, i32 36, i32 37, i32 38, i32 39, i32 40, i32 41, i32 42, i32 43, i32 44, i32 45, i32 46, i32 47, i32 48, i32 49, i32 50], align 4
 @arr2 = internal unnamed_addr constant [50 x i32] [i32 49, i32 48, i32 47, i32 46, i32 45, i32 44, i32 43, i32 42, i32 41, i32 40, i32 39, i32 38, i32 37, i32 36, i32 35, i32 34, i32 33, i32 32, i32 31, i32 30, i32 29, i32 28, i32 27, i32 26, i32 25, i32 24, i32 23, i32 22, i32 21, i32 20, i32 19, i32 18, i32 17, i32 16, i32 15, i32 14, i32 13, i32 12, i32 11, i32 10, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0], align 4
 
+; PR11034
 define i32 @test1() nounwind readnone {
 ; CHECK: test1
 entry:
@@ -31,3 +31,35 @@ for.body:                                         ; preds = %entry, %for.body
 for.end:                                          ; preds = %for.body
   ret i32 %add2
 }
+
+
+%struct.ListNode = type { %struct.ListNode*, i32 }
+
+@node5 = internal constant { %struct.ListNode*, i32, [4 x i8] } { %struct.ListNode* bitcast ({ %struct.ListNode*, i32, [4 x i8] }* @node4 to %struct.ListNode*), i32 4, [4 x i8] undef }, align 8
+@node4 = internal constant { %struct.ListNode*, i32, [4 x i8] } { %struct.ListNode* bitcast ({ %struct.ListNode*, i32, [4 x i8] }* @node3 to %struct.ListNode*), i32 3, [4 x i8] undef }, align 8
+@node3 = internal constant { %struct.ListNode*, i32, [4 x i8] } { %struct.ListNode* bitcast ({ %struct.ListNode*, i32, [4 x i8] }* @node2 to %struct.ListNode*), i32 2, [4 x i8] undef }, align 8
+@node2 = internal constant { %struct.ListNode*, i32, [4 x i8] } { %struct.ListNode* bitcast ({ %struct.ListNode*, i32, [4 x i8] }* @node1 to %struct.ListNode*), i32 1, [4 x i8] undef }, align 8
+@node1 = internal constant { %struct.ListNode*, i32, [4 x i8] } { %struct.ListNode* null, i32 0, [4 x i8] undef }, align 8
+
+define i32 @test2() nounwind uwtable readonly {
+; CHECK: test2
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %sum.02 = phi i32 [ 0, %entry ], [ %add, %for.body ]
+; CHECK: -->  %sum.02{{ *}}Exits: 10
+  %n.01 = phi %struct.ListNode* [ bitcast ({ %struct.ListNode*, i32, [4 x i8] }* @node5 to %struct.ListNode*), %entry ], [ %1, %for.body ]
+; CHECK: -->  %n.01{{ *}}Exits: @node1
+  %i = getelementptr inbounds %struct.ListNode* %n.01, i64 0, i32 1
+  %0 = load i32* %i, align 4
+  %add = add nsw i32 %0, %sum.02
+  %next = getelementptr inbounds %struct.ListNode* %n.01, i64 0, i32 0
+  %1 = load %struct.ListNode** %next, align 8
+; CHECK: -->  %1{{ *}}Exits: 0
+  %cmp = icmp eq %struct.ListNode* %1, null
+  br i1 %cmp, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  ret i32 %add
+}