[DebugInfo][Dexter] Unreachable line stepped onto after SimplifyCFG.
When SimplifyCFG changes the PHI node into a select instruction, the debug line records becomes ambiguous. It causes the debugger to display unreachable source lines.
Differential Revision: https://reviews.llvm.org/D53287
llvm-svn: 345250
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 1153f3c..82fb765 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -2529,6 +2529,47 @@
DII->eraseFromParent();
}
+void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt,
+ BasicBlock *BB) {
+ // Since we are moving the instructions out of its basic block, we do not
+ // retain their original debug locations (DILocations) and debug intrinsic
+ // instructions (dbg.values).
+ //
+ // Doing so would degrade the debugging experience and adversely affect the
+ // accuracy of profiling information.
+ //
+ // Currently, when hoisting the instructions, we take the following actions:
+ // - Remove their dbg.values.
+ // - Set their debug locations to the values from the insertion point.
+ //
+ // As per PR39141 (comment #8), the more fundamental reason why the dbg.values
+ // need to be deleted, is because there will not be any instructions with a
+ // DILocation in either branch left after performing the transformation. We
+ // can only insert a dbg.value after the two branches are joined again.
+ //
+ // See PR38762, PR39243 for more details.
+ //
+ // TODO: Extend llvm.dbg.value to take more than one SSA Value (PR39141) to
+ // encode predicated DIExpressions that yield different results on different
+ // code paths.
+ for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE;) {
+ Instruction *I = &*II;
+ I->dropUnknownNonDebugMetadata();
+ if (I->isUsedByMetadata())
+ dropDebugUsers(*I);
+ if (isa<DbgVariableIntrinsic>(I)) {
+ // Remove DbgInfo Intrinsics.
+ II = I->eraseFromParent();
+ continue;
+ }
+ I->setDebugLoc(InsertPt->getDebugLoc());
+ ++II;
+ }
+ DomBlock->getInstList().splice(InsertPt->getIterator(), BB->getInstList(),
+ BB->begin(),
+ BB->getTerminator()->getIterator());
+}
+
namespace {
/// A potential constituent of a bitreverse or bswap expression. See