| 1 | //===- StripGCRelocates.cpp - Remove gc.relocates inserted by RewriteStatePoints===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This is a little utility pass that removes the gc.relocates inserted by |
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| 10 | // RewriteStatepointsForGC. Note that the generated IR is incorrect, |
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| 11 | // but this is useful as a single pass in itself, for analysis of IR, without |
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| 12 | // the GC.relocates. The statepoint and gc.result intrinsics would still be |
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| 13 | // present. |
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| 14 | //===----------------------------------------------------------------------===// |
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| 15 | |
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| 16 | #include "llvm/Transforms/Utils/StripGCRelocates.h" |
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| 17 | #include "llvm/IR/Function.h" |
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| 18 | #include "llvm/IR/InstIterator.h" |
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| 19 | #include "llvm/IR/Instructions.h" |
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| 20 | #include "llvm/IR/Statepoint.h" |
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| 21 | |
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| 22 | using namespace llvm; |
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| 23 | |
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| 24 | static bool stripGCRelocates(Function &F) { |
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| 25 | // Nothing to do for declarations. |
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| 26 | if (F.isDeclaration()) |
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| 27 | return false; |
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| 28 | SmallVector<GCRelocateInst *, 20> GCRelocates; |
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| 29 | // TODO: We currently do not handle gc.relocates that are in landing pads, |
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| 30 | // i.e. not bound to a single statepoint token. |
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| 31 | for (Instruction &I : instructions(F)) { |
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| 32 | if (auto *GCR = dyn_cast<GCRelocateInst>(Val: &I)) |
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| 33 | if (isa<GCStatepointInst>(Val: GCR->getOperand(i_nocapture: 0))) |
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| 34 | GCRelocates.push_back(Elt: GCR); |
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| 35 | } |
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| 36 | // All gc.relocates are bound to a single statepoint token. The order of |
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| 37 | // visiting gc.relocates for deletion does not matter. |
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| 38 | for (GCRelocateInst *GCRel : GCRelocates) { |
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| 39 | Value *OrigPtr = GCRel->getDerivedPtr(); |
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| 40 | Value *ReplaceGCRel = OrigPtr; |
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| 41 | |
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| 42 | // All gc_relocates are i8 addrspace(1)* typed, we need a bitcast from i8 |
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| 43 | // addrspace(1)* to the type of the OrigPtr, if the are not the same. |
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| 44 | if (GCRel->getType() != OrigPtr->getType()) |
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| 45 | ReplaceGCRel = new BitCastInst(OrigPtr, GCRel->getType(), "cast" , GCRel->getIterator()); |
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| 46 | |
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| 47 | // Replace all uses of gc.relocate and delete the gc.relocate |
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| 48 | // There maybe unncessary bitcasts back to the OrigPtr type, an instcombine |
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| 49 | // pass would clear this up. |
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| 50 | GCRel->replaceAllUsesWith(V: ReplaceGCRel); |
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| 51 | GCRel->eraseFromParent(); |
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| 52 | } |
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| 53 | return !GCRelocates.empty(); |
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| 54 | } |
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| 55 | |
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| 56 | PreservedAnalyses StripGCRelocates::run(Function &F, |
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| 57 | FunctionAnalysisManager &AM) { |
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| 58 | if (!stripGCRelocates(F)) |
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| 59 | return PreservedAnalyses::all(); |
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| 60 | |
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| 61 | // Removing gc.relocate preserves the CFG, but most other analysis probably |
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| 62 | // need to re-run. |
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| 63 | PreservedAnalyses PA; |
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| 64 | PA.preserveSet<CFGAnalyses>(); |
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| 65 | return PA; |
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| 66 | } |
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| 67 | |
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