diff options
Diffstat (limited to 'lib/CodeGen')
| -rw-r--r-- | lib/CodeGen/MachineBlockPlacement.cpp | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp index bfba503..4b0f7f3 100644 --- a/lib/CodeGen/MachineBlockPlacement.cpp +++ b/lib/CodeGen/MachineBlockPlacement.cpp @@ -991,6 +991,28 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { Cond.clear(); MachineBasicBlock *TBB = 0, *FBB = 0; // For AnalyzeBranch. if (!TII->AnalyzeBranch(*PrevBB, TBB, FBB, Cond)) { + // The "PrevBB" is not yet updated to reflect current code layout, so, + // o. it may fall-through to a block without explict "goto" instruction + // before layout, and no longer fall-through it after layout; or + // o. just opposite. + // + // AnalyzeBranch() may return erroneous value for FBB when these two + // situations take place. For the first scenario FBB is mistakenly set + // NULL; for the 2nd scenario, the FBB, which is expected to be NULL, + // is mistakenly pointing to "*BI". + // + bool needUpdateBr = true; + if (!Cond.empty() && (!FBB || FBB == *BI)) { + PrevBB->updateTerminator(); + needUpdateBr = false; + Cond.clear(); + TBB = FBB = 0; + if (TII->AnalyzeBranch(*PrevBB, TBB, FBB, Cond)) { + // FIXME: This should never take place. + TBB = FBB = 0; + } + } + // If PrevBB has a two-way branch, try to re-order the branches // such that we branch to the successor with higher weight first. if (TBB && !Cond.empty() && FBB && @@ -1003,8 +1025,10 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) { DebugLoc dl; // FIXME: this is nowhere TII->RemoveBranch(*PrevBB); TII->InsertBranch(*PrevBB, FBB, TBB, Cond, dl); + needUpdateBr = true; } - PrevBB->updateTerminator(); + if (needUpdateBr) + PrevBB->updateTerminator(); } } |