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[SCEV] Don't infinitely recurse on unreachable code 

llvm-svn: 277848
This commit is contained in:
Sanjoy Das 2016-08-05 18:34:14 +00:00
parent 2a04a99ce6
commit b0b4e86215
2 changed files with 31 additions and 1 deletions
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4
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -4168,7 +4168,9 @@ static bool BrPHIToSelect(DominatorTree &DT, BranchInst *BI, PHINode *Merge,
} }
const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) { const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) {
if (PN->getNumIncomingValues() == 2) { auto IsReachable =
[&](BasicBlock *BB) { return DT.isReachableFromEntry(BB); };
if (PN->getNumIncomingValues() == 2 && all_of(PN->blocks(), IsReachable)) {
const Loop *L = LI.getLoopFor(PN->getParent()); const Loop *L = LI.getLoopFor(PN->getParent());
// We don't want to break LCSSA, even in a SCEV expression tree. // We don't want to break LCSSA, even in a SCEV expression tree.

28
llvm/test/Analysis/ScalarEvolution/smax-br-phi-idioms.ll
View File

@ -126,3 +126,31 @@ for.cond.0:
ret i32 %init ret i32 %init
} }
define i32 @f6(i32 %x, i32 %y) {
; Do the right thing for unreachable code:
; CHECK-LABEL: Classifying expressions for: @f6
entry:
%c0 = icmp sgt i32 %y, 0
%sum = add i32 %x, %y
br i1 %c0, label %merge, label %leave_1
merge:
%v0 = phi i32 [ %sum, %entry ], [ %v1, %unreachable ]
%c1 = icmp slt i32 %y, 0
br i1 %c1, label %leave_0, label %leave_0_cond
leave_0_cond:
br label %leave_0
leave_0:
%v1 = phi i32 [ %v0, %merge ], [ 0, %leave_0_cond ]
ret i32 0
leave_1:
ret i32 0
unreachable:
br label %merge
}