From 6ee8d17bc61d6a7e479b349d7f48edeabe61791f Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Sun, 4 Jan 2015 07:06:53 +0000 Subject: ValueTracking: ComputeNumSignBits should tolerate misshapen phi nodes PHI nodes can have zero operands in the middle of a transform. It is expected that utilities in Analysis don't freak out when this happens. Note that it is considered invalid to allow these misshapen phi nodes to make it to another pass. This fixes PR22086. llvm-svn: 225126 --- llvm/lib/Analysis/ValueTracking.cpp | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'llvm/lib/Analysis/ValueTracking.cpp') diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 6fdf4afebc2..b292af6cee7 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -1821,13 +1821,16 @@ unsigned ComputeNumSignBits(Value *V, const DataLayout *TD, case Instruction::PHI: { PHINode *PN = cast(U); + unsigned NumIncomingValues = PN->getNumIncomingValues(); // Don't analyze large in-degree PHIs. - if (PN->getNumIncomingValues() > 4) break; + if (NumIncomingValues > 4) break; + // Unreachable blocks may have zero-operand PHI nodes. + if (NumIncomingValues == 0) break; // Take the minimum of all incoming values. This can't infinitely loop // because of our depth threshold. Tmp = ComputeNumSignBits(PN->getIncomingValue(0), TD, Depth+1, Q); - for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) { + for (unsigned i = 1, e = NumIncomingValues; i != e; ++i) { if (Tmp == 1) return Tmp; Tmp = std::min(Tmp, ComputeNumSignBits(PN->getIncomingValue(i), TD, -- cgit v1.2.3