[llvm] r280901 - [LoopUnroll] Properly update loop-info when cloning prologues and epilogues.
Michael Zolotukhin via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 7 18:52:26 PDT 2016
Author: mzolotukhin
Date: Wed Sep 7 20:52:26 2016
New Revision: 280901
URL: http://llvm.org/viewvc/llvm-project?rev=280901&view=rev
Log:
[LoopUnroll] Properly update loop-info when cloning prologues and epilogues.
Summary:
When cloning blocks for prologue/epilogue we need to replicate the loop
structure from the original loop. It wasn't a problem for the innermost
loops, but it led to an incorrect loop info when we unrolled a loop with
a child loop - in this case created prologue-loop had a child loop, but
loop info didn't reflect that.
This fixes PR28888.
Reviewers: chandlerc, sanjoy, hfinkel
Subscribers: llvm-commits, silvas
Differential Revision: https://reviews.llvm.org/D24203
Added:
llvm/trunk/test/Transforms/LoopUnroll/pr28888.ll
Modified:
llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
Modified: llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp?rev=280901&r1=280900&r2=280901&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp Wed Sep 7 20:52:26 2016
@@ -291,15 +291,10 @@ static void CloneLoopBlocks(Loop *L, Val
Function *F = Header->getParent();
LoopBlocksDFS::RPOIterator BlockBegin = LoopBlocks.beginRPO();
LoopBlocksDFS::RPOIterator BlockEnd = LoopBlocks.endRPO();
- Loop *NewLoop = nullptr;
Loop *ParentLoop = L->getParentLoop();
- if (CreateRemainderLoop) {
- NewLoop = new Loop();
- if (ParentLoop)
- ParentLoop->addChildLoop(NewLoop);
- else
- LI->addTopLevelLoop(NewLoop);
- }
+
+ // The map from original loops to their cloned copies.
+ SmallDenseMap<const Loop *, Loop *, 4> NewLoops;
// For each block in the original loop, create a new copy,
// and update the value map with the newly created values.
@@ -307,10 +302,57 @@ static void CloneLoopBlocks(Loop *L, Val
BasicBlock *NewBB = CloneBasicBlock(*BB, VMap, "." + suffix, F);
NewBlocks.push_back(NewBB);
+ // Figure out which loop NewBB is in.
+ auto findClonedLoop = [&](const Loop *OldLoop) {
+ Loop *&NewLoop = NewLoops[OldLoop];
+ // If we've encountered this loop before, return it right away.
+ if (NewLoop)
+ return NewLoop;
+
+ // If BB is from L, and we're not creating a remainder, the loop for
+ // NewBB will be ParentLoop, which might be null. Update NewLoops map and
+ // return ParentLoop.
+ if (OldLoop == L && !CreateRemainderLoop)
+ return (NewLoop = ParentLoop);
+
+ // Now we know that there should be a cloned counterpart for OldLoop, but
+ // we haven't seen it yet. Note that OldLoop might be L if we're
+ // generating a remainder loop, or it can be an inner loop of L - in this
+ // case we'll recreate the loop structure of L in its clone.
+
+ // This is a first block belonging to OldLoop encountered in our RPO
+ // traversal.
+ assert(*BB == OldLoop->getHeader() && "Header should be first in RPO");
+
+ NewLoop = new Loop;
+ Loop *OldLoopParent = OldLoop->getParentLoop();
+ // If OldLoop has a parent loop, we have two options:
+ // 1. ParentLoop is the parent of L. It won't be cloned, and it will
+ // be a parent for NewLoop too.
+ // 2. ParentLoop is not a parent of L. In this case, it should be one
+ // of the cloned loops and we should be able to find it in our map.
+ //
+ // If OldLoop doesn't have a parent, then NewLoop should be yet another
+ // top-level loop.
+ if (OldLoopParent) {
+ Loop *NewLoopParent = ParentLoop == OldLoopParent
+ ? ParentLoop
+ : NewLoops.lookup(OldLoopParent);
+ assert(NewLoopParent && "Expected parent loop before sub-loop in RPO");
+ NewLoopParent->addChildLoop(NewLoop);
+ } else
+ LI->addTopLevelLoop(NewLoop);
+ return NewLoop;
+ };
+
+ Loop *NewLoop = findClonedLoop(LI->getLoopFor(*BB));
+
+ assert(NewLoop ||
+ (!CreateRemainderLoop && !ParentLoop) &&
+ "NewLoop can only be null if we are cloning top-level loop "
+ "without creating a remainder loop.");
if (NewLoop)
NewLoop->addBasicBlockToLoop(NewBB, *LI);
- else if (ParentLoop)
- ParentLoop->addBasicBlockToLoop(NewBB, *LI);
VMap[*BB] = NewBB;
if (Header == *BB) {
@@ -369,7 +411,8 @@ static void CloneLoopBlocks(Loop *L, Val
NewPHI->setIncomingValue(idx, V);
}
}
- if (NewLoop) {
+ if (CreateRemainderLoop) {
+ Loop *NewLoop = NewLoops[L];
// Add unroll disable metadata to disable future unrolling for this loop.
SmallVector<Metadata *, 4> MDs;
// Reserve first location for self reference to the LoopID metadata node.
Added: llvm/trunk/test/Transforms/LoopUnroll/pr28888.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnroll/pr28888.ll?rev=280901&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/pr28888.ll (added)
+++ llvm/trunk/test/Transforms/LoopUnroll/pr28888.ll Wed Sep 7 20:52:26 2016
@@ -0,0 +1,44 @@
+; RUN: opt -loop-unroll -verify-loop-info -unroll-runtime-epilog=false -unroll-count=4 -S < %s | FileCheck %s -check-prefix=PROLOG
+; RUN: opt -loop-unroll -verify-loop-info -unroll-runtime-epilog=true -unroll-count=4 -S < %s | FileCheck %s -check-prefix=EPILOG
+
+; PR28888
+; Check that loop info is correct if we unroll an outer loop, and thus the
+; remainder loop has a child loop.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; PROLOG-LABEL: @foo
+; EPILOG-LABEL: @foo
+define void @foo(i1 %x) #0 {
+bb:
+ br label %bb1
+
+bb1:
+ br label %bb2
+
+; PROLOG: bb2.prol:
+; EPILOG: bb2.epil:
+bb2:
+ %tmp = phi i64 [ 0, %bb1 ], [ %tmp2, %bb5 ]
+ br label %bb3
+
+bb3:
+ br label %bb4
+
+bb4:
+ br i1 %x, label %bb3, label %bb5
+
+; PROLOG: bb5.3:
+; EPILOG: bb5.3:
+bb5:
+ %tmp2 = add nuw nsw i64 %tmp, 1
+ %tmp3 = trunc i64 %tmp2 to i32
+ %tmp4 = icmp eq i32 %tmp3, undef
+ br i1 %tmp4, label %bb6, label %bb2
+
+bb6:
+ br label %bb1
+}
+
+attributes #0 = { "target-cpu"="x86-64" }
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