From 9af22722726c99e8435d499c5a1d661f91e6e7b3 Mon Sep 17 00:00:00 2001 From: Bob Wilson Date: Fri, 18 Jun 2010 17:07:23 +0000 Subject: [PATCH] Fix PR7372: Conditional branches (at least on ARM) are treated as predicated, so when IfConverter::CopyAndPredicateBlock checks to see if it should ignore an instruction because it is a branch, it should not check if the branch is predicated. This case (when IgnoreBr is true) is only relevant from IfConvertTriangle, where new branches are inserted after the block has been copied and predicated. If the original branch is not removed, we end up with multiple conditional branches (possibly conflicting) at the end of the block. Aside from any immediate errors resulting from that, this confuses the AnalyzeBranch functions so that the branches are not analyzable. That in turn causes the IfConverter to think that the "Simple" pattern can be applied, and things go downhill fast because the "Simple" pattern does _not_ apply if the block can fall through. This is pretty fragile. If there are other degenerate cases where AnalyzeBranch fails, but where the block may still fall through, the IfConverter should not perform its "Simple" if-conversion. But, I don't know how to do that with the current AnalyzeBranch interface, so for now, the best thing seems to be to avoid creating branches that AnalyzeBranch cannot handle. Evan, please review! llvm-svn: 106291 --- lib/CodeGen/IfConversion.cpp | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp index ed652a6020a..f82b2f09f36 100644 --- a/lib/CodeGen/IfConversion.cpp +++ b/lib/CodeGen/IfConversion.cpp @@ -1298,16 +1298,15 @@ void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI, for (MachineBasicBlock::iterator I = FromBBI.BB->begin(), E = FromBBI.BB->end(); I != E; ++I) { const TargetInstrDesc &TID = I->getDesc(); - bool isPredicated = TII->isPredicated(I); // Do not copy the end of the block branches. - if (IgnoreBr && !isPredicated && TID.isBranch()) + if (IgnoreBr && TID.isBranch()) break; MachineInstr *MI = MF.CloneMachineInstr(I); ToBBI.BB->insert(ToBBI.BB->end(), MI); ToBBI.NonPredSize++; - if (!isPredicated && !MI->isDebugValue()) { + if (!TII->isPredicated(I) && !MI->isDebugValue()) { if (!TII->PredicateInstruction(MI, Cond)) { #ifndef NDEBUG dbgs() << "Unable to predicate " << *I << "!\n";