https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/80729
resolves llvm/llvm-project#80699 >From 29a91711a135622cf74989e100274ab46c8c0bc1 Mon Sep 17 00:00:00 2001 From: Jeremy Morse <jeremy.mo...@sony.com> Date: Wed, 24 Jan 2024 17:45:43 +0000 Subject: [PATCH] [BPI] Transfer value-handles when assign/move constructing BPI (#77774) Background: BPI stores a collection of edge branch-probabilities, and also a set of Callback value-handles for the blocks in the edge-collection. When a block is deleted, BPI's eraseBlock method is called to clear the edge-collection of references to that block, to avoid dangling pointers. However, when move-constructing or assigning a BPI object, the edge-collection gets moved, but the value-handles are discarded. This can lead to to stale entries in the edge-collection when blocks are deleted without the callback -- not normally a problem, but if a new block is allocated with the same address as an old block, spurious branch probabilities will be recorded about it. The fix is to transfer the handles from the source BPI object. This was exposed by an unrelated debug-info change, it probably just shifted around allocation orders to expose this. Detected as nondeterminism and reduced by Zequan Wu: https://github.com/llvm/llvm-project/commit/f1b0a544514f3d343f32a41de9d6fb0b6cbb6021#commitcomment-136737090 (No test because IMHO testing for a behaviour that varies with memory allocators is likely futile; I can add the reproducer with a CHECK for the relevant branch weights if it's desired though) (cherry picked from commit 604a6c409e8473b212952b8633d92bbdb22a45c9) --- llvm/include/llvm/Analysis/BranchProbabilityInfo.h | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/llvm/include/llvm/Analysis/BranchProbabilityInfo.h b/llvm/include/llvm/Analysis/BranchProbabilityInfo.h index 6b9d178182011..91e1872e9bd6f 100644 --- a/llvm/include/llvm/Analysis/BranchProbabilityInfo.h +++ b/llvm/include/llvm/Analysis/BranchProbabilityInfo.h @@ -122,16 +122,23 @@ class BranchProbabilityInfo { } BranchProbabilityInfo(BranchProbabilityInfo &&Arg) - : Probs(std::move(Arg.Probs)), LastF(Arg.LastF), - EstimatedBlockWeight(std::move(Arg.EstimatedBlockWeight)) {} + : Handles(std::move(Arg.Handles)), Probs(std::move(Arg.Probs)), + LastF(Arg.LastF), + EstimatedBlockWeight(std::move(Arg.EstimatedBlockWeight)) { + for (auto &Handle : Handles) + Handle.setBPI(this); + } BranchProbabilityInfo(const BranchProbabilityInfo &) = delete; BranchProbabilityInfo &operator=(const BranchProbabilityInfo &) = delete; BranchProbabilityInfo &operator=(BranchProbabilityInfo &&RHS) { releaseMemory(); + Handles = std::move(RHS.Handles); Probs = std::move(RHS.Probs); EstimatedBlockWeight = std::move(RHS.EstimatedBlockWeight); + for (auto &Handle : Handles) + Handle.setBPI(this); return *this; } @@ -279,6 +286,8 @@ class BranchProbabilityInfo { } public: + void setBPI(BranchProbabilityInfo *BPI) { this->BPI = BPI; } + BasicBlockCallbackVH(const Value *V, BranchProbabilityInfo *BPI = nullptr) : CallbackVH(const_cast<Value *>(V)), BPI(BPI) {} }; _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
