forked from OSchip/llvm-project
Speculatively revert commits 142790 and 142843 to see if it fixes
the dragonegg and llvm-gcc self-host buildbots. Original commit
messages:
- 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;
}
- Now that we look at all the header PHIs, we need to consider all the header PHIs
when deciding that the loop has stopped evolving. Fixes miscompile in the gcc
torture testsuite!
llvm-svn: 142916
This commit is contained in:
Duncan Sands
parent
2ab33d28a8
commit
805c5b92c8
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@ -4844,12 +4844,12 @@ ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
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// EvaluateExpression adds non-phi values to the CurrentIterVals map.
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DenseMap<Instruction *, Constant *> NextIterVals;
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Constant *NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
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if (NextPHI == CurrentIterVals[PN])
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return RetVal = NextPHI; // Stopped evolving!
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if (NextPHI == 0)
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return 0; // Couldn't evaluate!
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NextIterVals[PN] = NextPHI;
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bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
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// Also evaluate the other PHI nodes. However, we don't get to stop if we
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// cease to be able to evaluate one of them or if they stop evolving,
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// because that doesn't necessarily prevent us from computing PN.
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@ -4858,19 +4858,11 @@ ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
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PHINode *PHI = dyn_cast<PHINode>(I->first);
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if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
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Constant *&NextPHI = NextIterVals[PHI];
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if (!NextPHI) { // Not already computed.
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if (NextPHI) continue; // Already computed!
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Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
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NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
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}
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if (NextPHI != I->second)
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StoppedEvolving = false;
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}
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// If all entries in CurrentIterVals == NextIterVals then we can stop
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// iterating, the loop can't continue to change.
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if (StoppedEvolving)
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return RetVal = CurrentIterVals[PN];
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CurrentIterVals.swap(NextIterVals);
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}
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}
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@ -4890,33 +4882,29 @@ const SCEV *ScalarEvolution::ComputeExitCountExhaustively(const Loop *L,
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// That's the only form we support here.
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if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
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DenseMap<Instruction *, Constant *> CurrentIterVals;
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BasicBlock *Header = L->getHeader();
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assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!");
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// One entry must be a constant (coming in from outside of the loop), and the
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// second must be derived from the same PHI.
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bool SecondIsBackedge = L->contains(PN->getIncomingBlock(1));
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PHINode *PHI = 0;
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for (BasicBlock::iterator I = Header->begin();
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(PHI = dyn_cast<PHINode>(I)); ++I) {
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Constant *StartCST =
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dyn_cast<Constant>(PHI->getIncomingValue(!SecondIsBackedge));
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if (StartCST == 0) continue;
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CurrentIterVals[PHI] = StartCST;
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}
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if (!CurrentIterVals.count(PN))
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return getCouldNotCompute();
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dyn_cast<Constant>(PN->getIncomingValue(!SecondIsBackedge));
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if (StartCST == 0) return getCouldNotCompute(); // Must be a constant.
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Value *BEValue = PN->getIncomingValue(SecondIsBackedge);
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if (getConstantEvolvingPHI(BEValue, L) != PN &&
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!isa<Constant>(BEValue))
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return getCouldNotCompute(); // Not derived from same PHI.
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// Okay, we find a PHI node that defines the trip count of this loop. Execute
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// the loop symbolically to determine when the condition gets a value of
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// "ExitWhen".
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unsigned IterationNum = 0;
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unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
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for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
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for (Constant *PHIVal = StartCST;
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IterationNum != MaxIterations; ++IterationNum) {
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DenseMap<Instruction *, Constant *> PHIValMap;
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PHIValMap[PN] = PHIVal;
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ConstantInt *CondVal =
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dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, L,
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CurrentIterVals, TD));
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dyn_cast_or_null<ConstantInt>(EvaluateExpression(Cond, L, PHIValMap, TD));
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// Couldn't symbolically evaluate.
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if (!CondVal) return getCouldNotCompute();
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@ -4926,19 +4914,11 @@ const SCEV *ScalarEvolution::ComputeExitCountExhaustively(const Loop *L,
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return getConstant(Type::getInt32Ty(getContext()), IterationNum);
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}
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// Update all the PHI nodes for the next iteration.
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DenseMap<Instruction *, Constant *> NextIterVals;
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for (DenseMap<Instruction *, Constant *>::const_iterator
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I = CurrentIterVals.begin(), E = CurrentIterVals.end(); I != E; ++I){
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PHINode *PHI = dyn_cast<PHINode>(I->first);
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if (!PHI || PHI->getParent() != Header) continue;
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Constant *&NextPHI = NextIterVals[PHI];
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if (NextPHI) continue; // Already computed!
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Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
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NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
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}
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CurrentIterVals.swap(NextIterVals);
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// Compute the value of the PHI node for the next iteration.
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Constant *NextPHI = EvaluateExpression(BEValue, L, PHIValMap, TD);
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if (NextPHI == 0 || NextPHI == PHIVal)
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return getCouldNotCompute();// Couldn't evaluate or not making progress...
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PHIVal = NextPHI;
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}
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// Too many iterations were needed to evaluate.
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@ -1,4 +1,5 @@
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; RUN: opt -analyze -scalar-evolution < %s 2>&1 | FileCheck %s
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; PR11034
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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"
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target triple = "i386-pc-linux-gnu"
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@ -6,7 +7,6 @@ target triple = "i386-pc-linux-gnu"
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@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
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@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
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; PR11034
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define i32 @test1() nounwind readnone {
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; CHECK: test1
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entry:
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@ -31,35 +31,3 @@ for.body: ; preds = %entry, %for.body
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for.end: ; preds = %for.body
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ret i32 %add2
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}
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%struct.ListNode = type { %struct.ListNode*, i32 }
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@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
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@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
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@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
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@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
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@node1 = internal constant { %struct.ListNode*, i32, [4 x i8] } { %struct.ListNode* null, i32 0, [4 x i8] undef }, align 8
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define i32 @test2() nounwind uwtable readonly {
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; CHECK: test2
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%sum.02 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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; CHECK: --> %sum.02{{ *}}Exits: 10
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%n.01 = phi %struct.ListNode* [ bitcast ({ %struct.ListNode*, i32, [4 x i8] }* @node5 to %struct.ListNode*), %entry ], [ %1, %for.body ]
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; CHECK: --> %n.01{{ *}}Exits: @node1
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%i = getelementptr inbounds %struct.ListNode* %n.01, i64 0, i32 1
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%0 = load i32* %i, align 4
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%add = add nsw i32 %0, %sum.02
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%next = getelementptr inbounds %struct.ListNode* %n.01, i64 0, i32 0
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%1 = load %struct.ListNode** %next, align 8
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; CHECK: --> %1{{ *}}Exits: 0
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%cmp = icmp eq %struct.ListNode* %1, null
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br i1 %cmp, label %for.end, label %for.body
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for.end: ; preds = %for.body
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ret i32 %add
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}
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@ -1,29 +0,0 @@
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; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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@foo.a = internal constant [8 x i32] [i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7], align 16
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define i32 @foo() nounwind uwtable noinline {
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entry:
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br label %for.cond
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for.cond: ; preds = %for.inc, %entry
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%sum.0 = phi i32 [ 0, %entry ], [ %add, %for.inc ]
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; CHECK: --> %sum.0 Exits: 28
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
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%cmp = icmp ult i32 %i.0, 8
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br i1 %cmp, label %for.inc, label %for.end
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for.inc: ; preds = %for.cond
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%idxprom = sext i32 %i.0 to i64
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%arrayidx = getelementptr inbounds [8 x i32]* @foo.a, i64 0, i64 %idxprom
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%0 = load i32* %arrayidx, align 4
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%add = add nsw i32 %sum.0, %0
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%inc = add nsw i32 %i.0, 1
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br label %for.cond
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for.end: ; preds = %for.cond
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ret i32 %sum.0
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}
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