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LoopRotate: Also rotate loops with multiple exits.
The old PHI updating code in loop-rotate was replaced with SSAUpdater a while ago, it has no problems with comples PHIs. What had to be fixed is detecting whether a loop was already rotated and updating dominators when multiple exits were present. This change increases overall code size a bit, mostly due to additional loop unrolling opportunities. Passes test-suite and selfhost with -verify-dom-info. Fixes PR7447. Thanks to Andy for the input on the domtree updating code. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162912 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
parent
c81fe9cab5
commit
d70846ec1b
@ -24,6 +24,7 @@
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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#include "llvm/Transforms/Utils/ValueMapper.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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@ -256,6 +257,7 @@ bool LoopRotate::rotateLoop(Loop *L) {
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return false;
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BasicBlock *OrigHeader = L->getHeader();
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BasicBlock *OrigLatch = L->getLoopLatch();
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BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
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if (BI == 0 || BI->isUnconditional())
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@ -267,13 +269,9 @@ bool LoopRotate::rotateLoop(Loop *L) {
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if (!L->isLoopExiting(OrigHeader))
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return false;
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// Updating PHInodes in loops with multiple exits adds complexity.
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// Keep it simple, and restrict loop rotation to loops with one exit only.
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// In future, lift this restriction and support for multiple exits if
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// required.
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SmallVector<BasicBlock*, 8> ExitBlocks;
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L->getExitBlocks(ExitBlocks);
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if (ExitBlocks.size() > 1)
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// If the loop latch already contains a branch that leaves the loop then the
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// loop is already rotated.
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if (OrigLatch == 0 || L->isLoopExiting(OrigLatch))
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return false;
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// Check size of original header and reject loop if it is very big.
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@ -286,11 +284,10 @@ bool LoopRotate::rotateLoop(Loop *L) {
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// Now, this loop is suitable for rotation.
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BasicBlock *OrigPreheader = L->getLoopPreheader();
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BasicBlock *OrigLatch = L->getLoopLatch();
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// If the loop could not be converted to canonical form, it must have an
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// indirectbr in it, just give up.
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if (OrigPreheader == 0 || OrigLatch == 0)
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if (OrigPreheader == 0)
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return false;
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// Anything ScalarEvolution may know about this loop or the PHI nodes
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@ -298,6 +295,8 @@ bool LoopRotate::rotateLoop(Loop *L) {
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if (ScalarEvolution *SE = getAnalysisIfAvailable<ScalarEvolution>())
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SE->forgetLoop(L);
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DEBUG(dbgs() << "LoopRotation: rotating "; L->dump());
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// Find new Loop header. NewHeader is a Header's one and only successor
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// that is inside loop. Header's other successor is outside the
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// loop. Otherwise loop is not suitable for rotation.
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@ -408,10 +407,16 @@ bool LoopRotate::rotateLoop(Loop *L) {
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// Update DominatorTree to reflect the CFG change we just made. Then split
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// edges as necessary to preserve LoopSimplify form.
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if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
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// Since OrigPreheader now has the conditional branch to Exit block, it is
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// the dominator of Exit.
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DT->changeImmediateDominator(Exit, OrigPreheader);
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DT->changeImmediateDominator(NewHeader, OrigPreheader);
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// Everything that was dominated by the old loop header is now dominated
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// by the original loop preheader. Conceptually the header was merged
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// into the preheader, even though we reuse the actual block as a new
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// loop latch.
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DomTreeNode *OrigHeaderNode = DT->getNode(OrigHeader);
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SmallVector<DomTreeNode *, 8> HeaderChildren(OrigHeaderNode->begin(),
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OrigHeaderNode->end());
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DomTreeNode *OrigPreheaderNode = DT->getNode(OrigPreheader);
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for (unsigned I = 0, E = HeaderChildren.size(); I != E; ++I)
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DT->changeImmediateDominator(HeaderChildren[I], OrigPreheaderNode);
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// Update OrigHeader to be dominated by the new header block.
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DT->changeImmediateDominator(OrigHeader, OrigLatch);
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@ -440,6 +445,46 @@ bool LoopRotate::rotateLoop(Loop *L) {
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// Update OrigHeader to be dominated by the new header block.
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DT->changeImmediateDominator(NewHeader, OrigPreheader);
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DT->changeImmediateDominator(OrigHeader, OrigLatch);
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// Brute force incremental dominator tree update. Call
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// findNearestCommonDominator on all CFG predecessors of each child of the
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// original header.
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DomTreeNode *OrigHeaderNode = DT->getNode(OrigHeader);
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SmallVector<DomTreeNode *, 8> WorkList(OrigHeaderNode->begin(),
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OrigHeaderNode->end());
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while (!WorkList.empty()) {
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DomTreeNode *Node = WorkList.pop_back_val();
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BasicBlock *BB = Node->getBlock();
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BasicBlock *NearestDom = 0;
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for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;
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++PI) {
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BasicBlock *Pred = *PI;
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// We have to process predecessors of a node before we touch the
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// actual node. If one of the predecessors is in our worklist, put it
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// and the currently processed node on the worklist and go processing
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// the predecessor.
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SmallVectorImpl<DomTreeNode *>::iterator I =
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std::find(WorkList.begin(), WorkList.end(), DT->getNode(Pred));
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if (I != WorkList.end()) {
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WorkList.push_back(Node);
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std::swap(*I, WorkList.back());
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// The predecessor is now at the end of the worklist.
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NearestDom = 0;
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break;
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}
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// On the first iteration start with Pred, on the other iterations we
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// narrow it down to the nearest common dominator.
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if (!NearestDom)
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NearestDom = Pred;
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else
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NearestDom = DT->findNearestCommonDominator(NearestDom, Pred);
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}
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if (NearestDom)
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DT->changeImmediateDominator(BB, NearestDom);
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}
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}
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}
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@ -452,6 +497,8 @@ bool LoopRotate::rotateLoop(Loop *L) {
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// emitted code isn't too gross in this common case.
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MergeBlockIntoPredecessor(OrigHeader, this);
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DEBUG(dbgs() << "LoopRotation: into "; L->dump());
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++NumRotated;
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return true;
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}
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200
test/Transforms/LoopRotate/multiple-exits.ll
Normal file
200
test/Transforms/LoopRotate/multiple-exits.ll
Normal file
@ -0,0 +1,200 @@
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; RUN: opt -S -loop-rotate < %s -verify-loop-info -verify-dom-info | FileCheck %s
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
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target triple = "x86_64-apple-macosx10.8.0"
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; PR7447
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define i32 @test1([100 x i32]* nocapture %a) nounwind readonly {
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entry:
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br label %for.cond
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for.cond: ; preds = %for.cond1, %entry
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%sum.0 = phi i32 [ 0, %entry ], [ %sum.1, %for.cond1 ]
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%i.0 = phi i1 [ true, %entry ], [ false, %for.cond1 ]
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br i1 %i.0, label %for.cond1, label %return
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for.cond1: ; preds = %for.cond, %land.rhs
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%sum.1 = phi i32 [ %add, %land.rhs ], [ %sum.0, %for.cond ]
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%i.1 = phi i32 [ %inc, %land.rhs ], [ 0, %for.cond ]
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%cmp2 = icmp ult i32 %i.1, 100
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br i1 %cmp2, label %land.rhs, label %for.cond
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land.rhs: ; preds = %for.cond1
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%conv = zext i32 %i.1 to i64
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%arrayidx = getelementptr inbounds [100 x i32]* %a, i64 0, i64 %conv
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%0 = load i32* %arrayidx, align 4
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%add = add i32 %0, %sum.1
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%cmp4 = icmp ugt i32 %add, 1000
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%inc = add i32 %i.1, 1
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br i1 %cmp4, label %return, label %for.cond1
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return: ; preds = %for.cond, %land.rhs
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%retval.0 = phi i32 [ 1000, %land.rhs ], [ %sum.0, %for.cond ]
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ret i32 %retval.0
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; CHECK: @test1
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; CHECK: for.cond1.preheader:
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; CHECK: %sum.04 = phi i32 [ 0, %entry ], [ %sum.1.lcssa, %for.cond.loopexit ]
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; CHECK: br label %for.cond1
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; CHECK: for.cond1:
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; CHECK: %sum.1 = phi i32 [ %add, %land.rhs ], [ %sum.04, %for.cond1.preheader ]
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; CHECK: %i.1 = phi i32 [ %inc, %land.rhs ], [ 0, %for.cond1.preheader ]
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; CHECK: %cmp2 = icmp ult i32 %i.1, 100
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; CHECK: br i1 %cmp2, label %land.rhs, label %for.cond.loopexit
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}
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define void @test2(i32 %x) nounwind {
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entry:
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br label %for.cond
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for.cond: ; preds = %if.end, %entry
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %if.end ]
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%cmp = icmp eq i32 %i.0, %x
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br i1 %cmp, label %return.loopexit, label %for.body
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for.body: ; preds = %for.cond
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%call = tail call i32 @foo(i32 %i.0) nounwind
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%tobool = icmp eq i32 %call, 0
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br i1 %tobool, label %if.end, label %a
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if.end: ; preds = %for.body
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%call1 = tail call i32 @foo(i32 42) nounwind
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%inc = add i32 %i.0, 1
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br label %for.cond
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a: ; preds = %for.body
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%call2 = tail call i32 @bar(i32 1) nounwind
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br label %return
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return.loopexit: ; preds = %for.cond
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br label %return
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return: ; preds = %return.loopexit, %a
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ret void
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; CHECK: @test2
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; CHECK: if.end:
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; CHECK: %inc = add i32 %i.02, 1
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; CHECK: %cmp = icmp eq i32 %inc, %x
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; CHECK: br i1 %cmp, label %for.cond.return.loopexit_crit_edge, label %for.body
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}
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declare i32 @foo(i32)
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declare i32 @bar(i32)
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@_ZTIi = external constant i8*
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; Verify dominators.
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define void @test3(i32 %x) {
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entry:
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%cmp2 = icmp eq i32 0, %x
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br i1 %cmp2, label %try.cont.loopexit, label %for.body.lr.ph
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for.body.lr.ph: ; preds = %entry
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br label %for.body
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for.body: ; preds = %for.body.lr.ph, %for.inc
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%i.03 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.inc ]
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invoke void @_Z3fooi(i32 %i.03)
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to label %for.inc unwind label %lpad
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for.inc: ; preds = %for.body
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%inc = add i32 %i.03, 1
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%cmp = icmp eq i32 %inc, %x
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br i1 %cmp, label %for.cond.try.cont.loopexit_crit_edge, label %for.body
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lpad: ; preds = %for.body
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%0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
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catch i8* bitcast (i8** @_ZTIi to i8*)
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%1 = extractvalue { i8*, i32 } %0, 0
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%2 = extractvalue { i8*, i32 } %0, 1
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%3 = tail call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIi to i8*)) nounwind
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%matches = icmp eq i32 %2, %3
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br i1 %matches, label %catch, label %eh.resume
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catch: ; preds = %lpad
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%4 = tail call i8* @__cxa_begin_catch(i8* %1) nounwind
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br i1 true, label %invoke.cont2.loopexit, label %for.body.i.lr.ph
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for.body.i.lr.ph: ; preds = %catch
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br label %for.body.i
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for.body.i: ; preds = %for.body.i.lr.ph, %for.inc.i
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%i.0.i1 = phi i32 [ 0, %for.body.i.lr.ph ], [ %inc.i, %for.inc.i ]
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invoke void @_Z3fooi(i32 %i.0.i1)
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to label %for.inc.i unwind label %lpad.i
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for.inc.i: ; preds = %for.body.i
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%inc.i = add i32 %i.0.i1, 1
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%cmp.i = icmp eq i32 %inc.i, 0
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br i1 %cmp.i, label %for.cond.i.invoke.cont2.loopexit_crit_edge, label %for.body.i
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lpad.i: ; preds = %for.body.i
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%5 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
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catch i8* bitcast (i8** @_ZTIi to i8*)
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%6 = extractvalue { i8*, i32 } %5, 0
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%7 = extractvalue { i8*, i32 } %5, 1
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%matches.i = icmp eq i32 %7, %3
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br i1 %matches.i, label %catch.i, label %lpad1.body
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catch.i: ; preds = %lpad.i
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%8 = tail call i8* @__cxa_begin_catch(i8* %6) nounwind
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invoke void @_Z3barj(i32 0)
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to label %invoke.cont2.i unwind label %lpad1.i
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invoke.cont2.i: ; preds = %catch.i
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tail call void @__cxa_end_catch() nounwind
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br label %invoke.cont2
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lpad1.i: ; preds = %catch.i
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%9 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
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cleanup
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%10 = extractvalue { i8*, i32 } %9, 0
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%11 = extractvalue { i8*, i32 } %9, 1
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tail call void @__cxa_end_catch() nounwind
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br label %lpad1.body
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for.cond.i.invoke.cont2.loopexit_crit_edge: ; preds = %for.inc.i
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br label %invoke.cont2.loopexit
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invoke.cont2.loopexit: ; preds = %for.cond.i.invoke.cont2.loopexit_crit_edge, %catch
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br label %invoke.cont2
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invoke.cont2: ; preds = %invoke.cont2.loopexit, %invoke.cont2.i
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tail call void @__cxa_end_catch() nounwind
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br label %try.cont
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for.cond.try.cont.loopexit_crit_edge: ; preds = %for.inc
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br label %try.cont.loopexit
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try.cont.loopexit: ; preds = %for.cond.try.cont.loopexit_crit_edge, %entry
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br label %try.cont
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try.cont: ; preds = %try.cont.loopexit, %invoke.cont2
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ret void
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lpad1.body: ; preds = %lpad1.i, %lpad.i
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%exn.slot.0.i = phi i8* [ %10, %lpad1.i ], [ %6, %lpad.i ]
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%ehselector.slot.0.i = phi i32 [ %11, %lpad1.i ], [ %7, %lpad.i ]
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tail call void @__cxa_end_catch() nounwind
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br label %eh.resume
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eh.resume: ; preds = %lpad1.body, %lpad
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%exn.slot.0 = phi i8* [ %exn.slot.0.i, %lpad1.body ], [ %1, %lpad ]
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%ehselector.slot.0 = phi i32 [ %ehselector.slot.0.i, %lpad1.body ], [ %2, %lpad ]
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%lpad.val = insertvalue { i8*, i32 } undef, i8* %exn.slot.0, 0
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%lpad.val5 = insertvalue { i8*, i32 } %lpad.val, i32 %ehselector.slot.0, 1
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resume { i8*, i32 } %lpad.val5
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}
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declare void @_Z3fooi(i32)
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declare i32 @__gxx_personality_v0(...)
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declare i32 @llvm.eh.typeid.for(i8*) nounwind readnone
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declare i8* @__cxa_begin_catch(i8*)
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declare void @__cxa_end_catch()
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