Index: llvm/lib/Transforms/Utils/BasicBlockUtils.cpp =================================================================== --- llvm/lib/Transforms/Utils/BasicBlockUtils.cpp +++ llvm/lib/Transforms/Utils/BasicBlockUtils.cpp @@ -758,12 +758,22 @@ // The new block unconditionally branches to the old block. BranchInst *BI = BranchInst::Create(BB, NewBB); + + Loop *L = nullptr; + BasicBlock *OldLatch = nullptr; // Splitting the predecessors of a loop header creates a preheader block. - if (LI && LI->isLoopHeader(BB)) + if (LI && LI->isLoopHeader(BB)) { + L = LI->getLoopFor(BB); // Using the loop start line number prevents debuggers stepping into the // loop body for this instruction. - BI->setDebugLoc(LI->getLoopFor(BB)->getStartLoc()); - else + BI->setDebugLoc(L->getStartLoc()); + + // If BB is the header of the Loop, it is possible that the loop is + // modified, such that the current latch does not remain the latch of the + // loop. If that is the case, the loop metadata from the current latch needs + // to be applied to the new latch. + OldLatch = L->getLoopLatch(); + } else BI->setDebugLoc(BB->getFirstNonPHIOrDbg()->getDebugLoc()); // Move the edges from Preds to point to NewBB instead of BB. @@ -798,6 +808,15 @@ UpdatePHINodes(BB, NewBB, Preds, BI, HasLoopExit); } + if (L && OldLatch) { + BasicBlock *NewLatch = L->getLoopLatch(); + if (NewLatch != OldLatch) { + MDNode *MD = OldLatch->getTerminator()->getMetadata("llvm.loop"); + NewLatch->getTerminator()->setMetadata("llvm.loop", MD); + OldLatch->getTerminator()->setMetadata("llvm.loop", nullptr); + } + } + return NewBB; } Index: llvm/test/Transforms/LoopSimplify/update_latch_md.ll =================================================================== --- /dev/null +++ llvm/test/Transforms/LoopSimplify/update_latch_md.ll @@ -0,0 +1,47 @@ +; RUN: opt -loop-simplify -S < %s | FileCheck %s + +; This will test whether or not the metadata from the current loop 1 latch +; is removed, and applied to the new latch after running the loop-simplify +; pass on this function. The loop simplify pass ensures that each loop has exit +; blocks which only have predecessors that are inside of the loop. This +; guarantees that the loop preheader/header will dominate the exit blocks. For +; this function currently loop 2 does not have a dedicated exit block. + +; CHECK: loop_1_loopHeader.loopexit: +; CHECK: br label %loop_1_loopHeader, !llvm.loop [[LOOP_1_LATCH_MD:![0-9]+]] +; CHECK: loop_2_loopHeader +; CHECK: br i1 %grt_B, label %loop_1_loopHeader.loopexit, label %loop_2_do +; CHECK-NOT: br i1 %grt_B, label %loop_1_loopHeader, label %loop_2_do, !llvm.loop{{.*}} + +define void @function(i32 %A) { +entry: + %B = add i32 %A, 45 + %C = add i32 %A, 22 + br label %loop_1_loopHeader + +loop_1_loopHeader: ; preds = %loop_2_loopHeader, %entry + %loop_1_idx = phi i32 [ 1, %entry], [ %loop_1_update_idx, %loop_2_loopHeader ] + %grt_C = icmp slt i32 %loop_1_idx, %C + br i1 %grt_C, label %exit, label %loop_1_do + +loop_1_do: ; preds = %loop_1_loopHeader + %loop_1_update_idx = add nuw nsw i32 %loop_1_idx, 1 + br label %loop_2_loopHeader + +loop_2_loopHeader: ; preds = %loop_2_do, %_loop_1_do + %loop_2_idx = phi i32 [ 1, %loop_1_do ], [ %loop_2_update_idx, %loop_2_do ] + %grt_B = icmp slt i32 %loop_2_idx, %B + br i1 %grt_B, label %loop_1_loopHeader, label %loop_2_do, !llvm.loop !0 + +loop_2_do: ; preds = %loop_2_loopHeader + %loop_2_update_idx = add nuw nsw i32 %loop_2_idx, 1 + br label %loop_2_loopHeader, !llvm.loop !2 + +exit: ; preds = %loop_1_loopHeader + ret void +} + +!0 = distinct !{!0, !1} +!1 = !{!"llvm.loop.unroll.disable"} +!2 = distinct !{!2, !1} +