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<p class="MsoNormal">Currently SelectionDAGBuilder::visitBr() doesn’t emit unconditional fall-through branches (to next block) without reference of optimization level. So the following LLVM IR<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">entry:<o:p></o:p></p>
<p class="MsoNormal"> br label %return, !dbg !26<o:p></o:p></p>
<p class="MsoNormal">return: ; preds = %entry<o:p></o:p></p>
<p class="MsoNormal"> ret void, !dbg !27<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">has no generated DAG node for “br” instruction. If we are going to generate debug line table for this branch in -O0 mode, we should leave it in place. For example such a branch can be generated by a FE for some “return;” statement at the
end of void function or for one of “break;” statement if switch-related exit block is next to BB of the “break;”.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This change emits all unconditional branches in -O0 mode:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">--- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp<o:p></o:p></p>
<p class="MsoNormal">+++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp<o:p></o:p></p>
<p class="MsoNormal">@@ -1584,8 +1584,8 @@ void SelectionDAGBuilder::visitBr(const BranchInst<o:p></o:p></p>
<p class="MsoNormal"> // Update machine-CFG edges.<o:p></o:p></p>
<p class="MsoNormal"> BrMBB->addSuccessor(Succ0MBB);<o:p></o:p></p>
<p class="MsoNormal"><o:p></o:p></p>
<p class="MsoNormal">- // If this is not a fall-through branch, emit the branch.<o:p></o:p></p>
<p class="MsoNormal">- if (Succ0MBB != NextBlock)<o:p></o:p></p>
<p class="MsoNormal">+ // If this is not a fall-through branch or optimizations are off<o:p></o:p></p>
<p class="MsoNormal">+ if (Succ0MBB != NextBlock || CodeGenOpt::None == TM.getOptLevel())<o:p></o:p></p>
<p class="MsoNormal"> DAG.setRoot(DAG.getNode(ISD::BR, getCurSDLoc(),<o:p></o:p></p>
<p class="MsoNormal"> MVT::Other, getControlRoot(),<o:p></o:p></p>
<p class="MsoNormal"> DAG.getBasicBlock(Succ0MBB)));<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Daniil<o:p></o:p></p>
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