[llvm] r366050 - [Loop Peeling] Fix the bug with IDom setting for exit loops
Serguei Katkov via llvm-commits
llvm-commits at lists.llvm.org
Mon Jul 15 02:13:11 PDT 2019
Author: skatkov
Date: Mon Jul 15 02:13:11 2019
New Revision: 366050
URL: http://llvm.org/viewvc/llvm-project?rev=366050&view=rev
Log:
[Loop Peeling] Fix the bug with IDom setting for exit loops
It is possible that loop exit has two predecessors in a loop body.
In this case after the peeling the iDom of the exit should be a clone of
iDom of original exit but no a clone of a block coming to this exit.
Reviewers: reames, fhahn
Reviewed By: reames
Subscribers: hiraditya, zzheng, llvm-commits
Differential Revision: https://reviews.llvm.org/D64618
Added:
llvm/trunk/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll
Modified:
llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
Modified: llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp?rev=366050&r1=366049&r2=366050&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp Mon Jul 15 02:13:11 2019
@@ -583,6 +583,18 @@ bool llvm::peelLoop(Loop *L, unsigned Pe
SmallVector<std::pair<BasicBlock *, BasicBlock *>, 4> ExitEdges;
L->getExitEdges(ExitEdges);
+ DenseMap<BasicBlock *, BasicBlock *> ExitIDom;
+ if (DT) {
+ assert(L->hasDedicatedExits() && "No dedicated exits?");
+ for (auto Edge : ExitEdges) {
+ if (ExitIDom.count(Edge.second))
+ continue;
+ BasicBlock *BB = DT->getNode(Edge.second)->getIDom()->getBlock();
+ assert(L->contains(BB) && "IDom is not in a loop");
+ ExitIDom[Edge.second] = BB;
+ }
+ }
+
Function *F = Header->getParent();
// Set up all the necessary basic blocks. It is convenient to split the
@@ -675,9 +687,9 @@ bool llvm::peelLoop(Loop *L, unsigned Pe
// latter is the first cloned loop body, as original PreHeader dominates
// the original loop body.
if (Iter == 0)
- for (auto Edge : ExitEdges)
- DT->changeImmediateDominator(Edge.second,
- cast<BasicBlock>(LVMap[Edge.first]));
+ for (auto Exit : ExitIDom)
+ DT->changeImmediateDominator(Exit.first,
+ cast<BasicBlock>(LVMap[Exit.second]));
#ifdef EXPENSIVE_CHECKS
assert(DT->verify(DominatorTree::VerificationLevel::Fast));
#endif
@@ -719,6 +731,9 @@ bool llvm::peelLoop(Loop *L, unsigned Pe
// We modified the loop, update SE.
SE->forgetTopmostLoop(L);
+ // Finally DomtTree must be correct.
+ assert(DT->verify(DominatorTree::VerificationLevel::Fast));
+
// FIXME: Incrementally update loop-simplify
simplifyLoop(L, DT, LI, SE, AC, nullptr, PreserveLCSSA);
Added: llvm/trunk/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll?rev=366050&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll (added)
+++ llvm/trunk/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll Mon Jul 15 02:13:11 2019
@@ -0,0 +1,55 @@
+; REQUIRES: asserts
+; RUN: opt < %s -S -debug-only=loop-unroll -loop-unroll -unroll-runtime -unroll-peel-multi-deopt-exit 2>&1 | FileCheck %s
+; RUN: opt < %s -S -debug-only=loop-unroll -unroll-peel-multi-deopt-exit -passes='require<profile-summary>,function(require<opt-remark-emit>,unroll)' 2>&1 | FileCheck %s
+
+; Regression test for setting the correct idom for exit blocks.
+
+; CHECK: Loop Unroll: F[basic]
+; CHECK: PEELING loop %for.body with iteration count 1!
+
+define i32 @basic(i32* %p, i32 %k, i1 %c1, i1 %c2) #0 !prof !3 {
+entry:
+ %cmp3 = icmp slt i32 0, %k
+ br i1 %cmp3, label %for.body.lr.ph, label %for.end
+
+for.body.lr.ph: ; preds = %entry
+ br label %for.body
+
+for.body: ; preds = %for.body.lr.ph, %for.body
+ %i.05 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %latch ]
+ %p.addr.04 = phi i32* [ %p, %for.body.lr.ph ], [ %incdec.ptr, %latch ]
+ %incdec.ptr = getelementptr inbounds i32, i32* %p.addr.04, i32 1
+ store i32 %i.05, i32* %p.addr.04, align 4
+ %inc = add nsw i32 %i.05, 1
+ %cmp = icmp slt i32 %inc, %k
+ br i1 %c1, label %continue, label %to_side_exit
+
+continue:
+ br i1 %c2, label %latch, label %side_exit, !prof !2
+
+latch:
+ br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge, !prof !1
+
+for.cond.for.end_crit_edge: ; preds = %for.body
+ br label %for.end
+
+to_side_exit:
+ br i1 %c2, label %continue, label %side_exit, !prof !2
+
+
+for.end: ; preds = %for.cond.for.end_crit_edge, %entry
+ %res = phi i32 [ 0, %entry ], [ %inc, %for.cond.for.end_crit_edge ]
+ ret i32 %res
+
+side_exit:
+ %rval = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 %inc) ]
+ ret i32 %rval
+}
+
+declare i32 @llvm.experimental.deoptimize.i32(...)
+
+attributes #0 = { nounwind }
+
+!1 = !{!"branch_weights", i32 1, i32 1}
+!2 = !{!"branch_weights", i32 1, i32 0}
+!3 = !{!"function_entry_count", i64 1}
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