forked from OSchip/llvm-project
[RuntimeUnrolling] Update DomTree correctly when exit blocks have successors
Summary: When we runtime unroll with multiple exit blocks, we also need to update the immediate dominators of the immediate successors of the exit blocks. Reviewers: reames, mkuper, mzolotukhin, apilipenko Reviewed by: mzolotukhin Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D35304 llvm-svn: 307909
This commit is contained in:
Anna Thomas
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75ac75d01e
commit
ec9b326569
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@ -22,6 +22,7 @@
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/LoopIterator.h"
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#include "llvm/Analysis/LoopPass.h"
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@ -736,7 +737,9 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
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// remainder are connected to the original Loop's exit blocks. The remaining
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// work is to update the phi nodes in the original loop, and take in the
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// values from the cloned region. Also update the dominator info for
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// OtherExits, since we have new edges into OtherExits.
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// OtherExits and their immediate successors, since we have new edges into
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// OtherExits.
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SmallSet<BasicBlock*, 8> ImmediateSuccessorsOfExitBlocks;
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for (auto *BB : OtherExits) {
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for (auto &II : *BB) {
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@ -759,12 +762,35 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
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cast<BasicBlock>(VMap[Phi->getIncomingBlock(i)]));
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}
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}
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#ifdef EXPENSIVE_CHECKS
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for (BasicBlock *SuccBB : successors(BB)) {
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assert(!(any_of(OtherExits,
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[SuccBB](BasicBlock *EB) { return EB == SuccBB; }) ||
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SuccBB == LatchExit) &&
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"Breaks the definition of dedicated exits!");
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}
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#endif
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// Update the dominator info because the immediate dominator is no longer the
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// header of the original Loop. BB has edges both from L and remainder code.
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// Since the preheader determines which loop is run (L or directly jump to
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// the remainder code), we set the immediate dominator as the preheader.
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if (DT)
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if (DT) {
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DT->changeImmediateDominator(BB, PreHeader);
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// Also update the IDom for immediate successors of BB. If the current
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// IDom is the header, update the IDom to be the preheader because that is
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// the nearest common dominator of all predecessors of SuccBB. We need to
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// check for IDom being the header because successors of exit blocks can
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// have edges from outside the loop, and we should not incorrectly update
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// the IDom in that case.
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for (BasicBlock *SuccBB: successors(BB))
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if (ImmediateSuccessorsOfExitBlocks.insert(SuccBB).second) {
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if (DT->getNode(SuccBB)->getIDom()->getBlock() == Header) {
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assert(!SuccBB->getSinglePredecessor() &&
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"BB should be the IDom then!");
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DT->changeImmediateDominator(SuccBB, PreHeader);
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}
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}
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}
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}
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// Loop structure should be the following:
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@ -0,0 +1,126 @@
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; RUN: opt < %s -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=false -unroll-runtime-multi-exit=true -unroll-count=4 -verify-dom-info -S | FileCheck %s
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; REQUIRES: asserts
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; The tests below are for verifying dom tree after runtime unrolling
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; with multiple exit/exiting blocks.
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; We explicitly set the unroll count so that expensiveTripCount computation is allowed.
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; mergedexit block has edges from loop exit blocks.
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define i64 @test1() {
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; CHECK-LABEL: test1(
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; CHECK-LABEL: headerexit:
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; CHECK-NEXT: %addphi = phi i64 [ %add.iv, %header ], [ %add.iv.1, %header.1 ], [ %add.iv.2, %header.2 ], [ %add.iv.3, %header.3 ]
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; CHECK-NEXT: br label %mergedexit
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; CHECK-LABEL: latchexit:
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; CHECK-NEXT: %shftphi = phi i64 [ %shft, %latch ], [ %shft.1, %latch.1 ], [ %shft.2, %latch.2 ], [ %shft.3, %latch.3 ]
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; CHECK-NEXT: br label %mergedexit
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; CHECK-LABEL: mergedexit:
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; CHECK-NEXT: %retval = phi i64 [ %addphi, %headerexit ], [ %shftphi, %latchexit ]
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; CHECK-NEXT: ret i64 %retval
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entry:
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br label %preheader
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preheader: ; preds = %bb
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%trip = zext i32 undef to i64
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br label %header
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header: ; preds = %latch, %preheader
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%iv = phi i64 [ 2, %preheader ], [ %add.iv, %latch ]
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%add.iv = add nuw nsw i64 %iv, 2
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%cmp1 = icmp ult i64 %add.iv, %trip
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br i1 %cmp1, label %latch, label %headerexit
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latch: ; preds = %header
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%shft = ashr i64 %add.iv, 1
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%cmp2 = icmp ult i64 %shft, %trip
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br i1 %cmp2, label %header, label %latchexit
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headerexit: ; preds = %header
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%addphi = phi i64 [ %add.iv, %header ]
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br label %mergedexit
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latchexit: ; preds = %latch
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%shftphi = phi i64 [ %shft, %latch ]
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br label %mergedexit
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mergedexit: ; preds = %latchexit, %headerexit
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%retval = phi i64 [ %addphi, %headerexit ], [ %shftphi, %latchexit ]
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ret i64 %retval
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}
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; mergedexit has edges from loop exit blocks and a block outside the loop.
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define void @test2(i1 %cond, i32 %n) {
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; CHECK-LABEL: header.1:
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; CHECK-NEXT: %add.iv.1 = add nuw nsw i64 %add.iv, 2
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; CHECK: br i1 %cmp1.1, label %latch.1, label %headerexit
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; CHECK-LABEL: latch.3:
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; CHECK: %cmp2.3 = icmp ult i64 %shft.3, %trip
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; CHECK-NEXT: br i1 %cmp2.3, label %header, label %latchexit, !llvm.loop
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entry:
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br i1 %cond, label %preheader, label %mergedexit
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preheader: ; preds = %entry
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%trip = zext i32 %n to i64
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br label %header
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header: ; preds = %latch, %preheader
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%iv = phi i64 [ 2, %preheader ], [ %add.iv, %latch ]
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%add.iv = add nuw nsw i64 %iv, 2
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%cmp1 = icmp ult i64 %add.iv, %trip
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br i1 %cmp1, label %latch, label %headerexit
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latch: ; preds = %header
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%shft = ashr i64 %add.iv, 1
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%cmp2 = icmp ult i64 %shft, %trip
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br i1 %cmp2, label %header, label %latchexit
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headerexit: ; preds = %header
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br label %mergedexit
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latchexit: ; preds = %latch
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br label %mergedexit
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mergedexit: ; preds = %latchexit, %headerexit, %entry
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ret void
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}
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; exitsucc is from loop exit block only.
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define i64 @test3(i32 %n) {
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; CHECK-LABEL: test3(
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; CHECK-LABEL: headerexit:
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; CHECK-NEXT: br label %exitsucc
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; CHECK-LABEL: latchexit:
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; CHECK-NEXT: %shftphi = phi i64 [ %shft, %latch ], [ %shft.1, %latch.1 ], [ %shft.2, %latch.2 ], [ %shft.3, %latch.3 ]
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; CHECK-NEXT: ret i64 %shftphi
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; CHECK-LABEL: exitsucc:
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; CHECK-NEXT: ret i64 96
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entry:
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br label %preheader
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preheader: ; preds = %bb
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%trip = zext i32 %n to i64
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br label %header
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header: ; preds = %latch, %preheader
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%iv = phi i64 [ 2, %preheader ], [ %add.iv, %latch ]
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%add.iv = add nuw nsw i64 %iv, 2
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%cmp1 = icmp ult i64 %add.iv, %trip
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br i1 %cmp1, label %latch, label %headerexit
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latch: ; preds = %header
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%shft = ashr i64 %add.iv, 1
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%cmp2 = icmp ult i64 %shft, %trip
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br i1 %cmp2, label %header, label %latchexit
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headerexit: ; preds = %header
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br label %exitsucc
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latchexit: ; preds = %latch
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%shftphi = phi i64 [ %shft, %latch ]
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ret i64 %shftphi
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exitsucc: ; preds = %headerexit
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ret i64 96
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}
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