1/*========================== begin_copyright_notice ============================ 2 3Copyright (C) 2019-2021 Intel Corporation 4 5SPDX-License-Identifier: MIT 6 7============================= end_copyright_notice ===========================*/ 8 9From eeb816d95f0910bd246e37bb2bb3923acf0edf6b Mon Sep 17 00:00:00 2001 10From: Aleksander Us <aleksander.us@intel.com> 11Date: Mon, 26 Aug 2019 15:47:41 +0300 12Subject: [PATCH] [BasicBlockUtils] Add metadata fixing in 13 SplitBlockPredecessors. 14 15In case when BB is header of some loop and predecessor is latch of 16this loop, metadata was not attached to newly created basic block. 17This led to loss of loop metadata for other passes. 18--- 19 lib/Transforms/Utils/BasicBlockUtils.cpp | 23 ++++++++---- 20 test/Transforms/LoopSimplify/loop_metadata.ll | 36 +++++++++++++++++++ 21 2 files changed, 52 insertions(+), 7 deletions(-) 22 create mode 100644 test/Transforms/LoopSimplify/loop_metadata.ll 23 24diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp 25index 5fa371377c8..3a90ae061fb 100644 26--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp 27+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp 28@@ -579,24 +579,33 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB, 29 30 // The new block unconditionally branches to the old block. 31 BranchInst *BI = BranchInst::Create(BB, NewBB); 32+ bool IsBBHeader = LI && LI->isLoopHeader(BB); 33+ Loop *BBLoop = LI ? LI->getLoopFor(BB) : nullptr; 34 // Splitting the predecessors of a loop header creates a preheader block. 35- if (LI && LI->isLoopHeader(BB)) 36+ if (IsBBHeader) 37 // Using the loop start line number prevents debuggers stepping into the 38 // loop body for this instruction. 39- BI->setDebugLoc(LI->getLoopFor(BB)->getStartLoc()); 40+ BI->setDebugLoc(BBLoop->getStartLoc()); 41 else 42 BI->setDebugLoc(BB->getFirstNonPHIOrDbg()->getDebugLoc()); 43 44 // Move the edges from Preds to point to NewBB instead of BB. 45- for (unsigned i = 0, e = Preds.size(); i != e; ++i) { 46+ for (BasicBlock *Pred : Preds) { 47+ Instruction *PI = Pred->getTerminator(); 48 // This is slightly more strict than necessary; the minimum requirement 49 // is that there be no more than one indirectbr branching to BB. And 50 // all BlockAddress uses would need to be updated. 51- assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) && 52+ assert(!isa<IndirectBrInst>(PI) && 53 "Cannot split an edge from an IndirectBrInst"); 54- assert(!isa<CallBrInst>(Preds[i]->getTerminator()) && 55- "Cannot split an edge from a CallBrInst"); 56- Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB); 57+ assert(!isa<CallBrInst>(PI) && "Cannot split an edge from a CallBrInst"); 58+ if (IsBBHeader && BBLoop->contains(Pred) && BBLoop->isLoopLatch(Pred)) { 59+ // Update loop metadata if it exists. 60+ if (MDNode *LoopMD = PI->getMetadata(LLVMContext::MD_loop)) { 61+ BI->setMetadata(LLVMContext::MD_loop, LoopMD); 62+ PI->setMetadata(LLVMContext::MD_loop, nullptr); 63+ } 64+ } 65+ PI->replaceUsesOfWith(BB, NewBB); 66 } 67 68 // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI 69diff --git a/llvm/test/Transforms/LoopSimplify/loop_metadata.ll b/llvm/test/Transforms/LoopSimplify/loop_metadata.ll 70new file mode 100644 71index 00000000000..c15c92fe3ae 72--- /dev/null 73+++ b/llvm/test/Transforms/LoopSimplify/loop_metadata.ll 74@@ -0,0 +1,36 @@ 75+; RUN: opt -S -loop-simplify < %s | FileCheck %s 76+ 77+; CHECK: for.cond.loopexit: 78+; CHECK: br label %for.cond, !llvm.loop !0 79+; CHECK: br i1 %cmp1, label %for.body1, label %for.cond.loopexit 80+ 81+define void @foo() { 82+entry: 83+ br label %for.cond 84+ 85+for.cond: ; preds = %for.cond1, %entry 86+ %j = phi i32 [ 0, %entry ], [ %add, %for.cond1 ] 87+ %cmp = icmp ult i32 %j, 8 88+ br i1 %cmp, label %for.body, label %for.end 89+ 90+for.body: ; preds = %for.cond 91+ %dummy1 = add i32 1, 1 92+ %add = add nuw nsw i32 %j, 1 93+ br label %for.cond1 94+ 95+for.cond1: ; preds = %for.body1, %for.body 96+ %i.0 = phi i32 [ 1, %for.body ], [ %inc, %for.body1 ] 97+ %cmp1 = icmp ult i32 %i.0, 8 98+ br i1 %cmp1, label %for.body1, label %for.cond, !llvm.loop !0 99+ 100+for.body1: ; preds = %for.cond1 101+ %dummy2 = add i32 1, 1 102+ %inc = add nuw nsw i32 %i.0, 1 103+ br label %for.cond1 104+ 105+for.end: ; preds = %for.cond 106+ ret void 107+} 108+ 109+!0 = distinct !{!0, !1} 110+!1 = !{!"llvm.loop.unroll.full"} 111-- 1122.18.0 113 114