cedb9704bd
Verifying CFG invariants of a block before verifying its contents allows contents verification to rely on the CFG invariants (e.g. that there's a vector loop region that can be retrieved). This avoids extra checks in https://github.com/llvm/llvm-project/pull/76172.
308 lines
9.8 KiB
C++
308 lines
9.8 KiB
C++
//===-- VPlanVerifier.cpp -------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// This file defines the class VPlanVerifier, which contains utility functions
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/// to check the consistency and invariants of a VPlan.
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///
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//===----------------------------------------------------------------------===//
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#include "VPlanVerifier.h"
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#include "VPlan.h"
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#include "VPlanCFG.h"
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#include "VPlanDominatorTree.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/Support/CommandLine.h"
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#define DEBUG_TYPE "loop-vectorize"
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using namespace llvm;
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// Verify that phi-like recipes are at the beginning of \p VPBB, with no
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// other recipes in between. Also check that only header blocks contain
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// VPHeaderPHIRecipes.
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static bool verifyPhiRecipes(const VPBasicBlock *VPBB) {
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auto RecipeI = VPBB->begin();
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auto End = VPBB->end();
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unsigned NumActiveLaneMaskPhiRecipes = 0;
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const VPRegionBlock *ParentR = VPBB->getParent();
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bool IsHeaderVPBB = ParentR && !ParentR->isReplicator() &&
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ParentR->getEntryBasicBlock() == VPBB;
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while (RecipeI != End && RecipeI->isPhi()) {
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if (isa<VPActiveLaneMaskPHIRecipe>(RecipeI))
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NumActiveLaneMaskPhiRecipes++;
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if (IsHeaderVPBB && !isa<VPHeaderPHIRecipe, VPWidenPHIRecipe>(*RecipeI)) {
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errs() << "Found non-header PHI recipe in header VPBB";
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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errs() << ": ";
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RecipeI->dump();
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#endif
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return false;
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}
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if (!IsHeaderVPBB && isa<VPHeaderPHIRecipe>(*RecipeI)) {
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errs() << "Found header PHI recipe in non-header VPBB";
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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errs() << ": ";
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RecipeI->dump();
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#endif
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return false;
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}
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RecipeI++;
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}
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if (NumActiveLaneMaskPhiRecipes > 1) {
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errs() << "There should be no more than one VPActiveLaneMaskPHIRecipe";
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return false;
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}
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while (RecipeI != End) {
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if (RecipeI->isPhi() && !isa<VPBlendRecipe>(&*RecipeI)) {
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errs() << "Found phi-like recipe after non-phi recipe";
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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errs() << ": ";
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RecipeI->dump();
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errs() << "after\n";
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std::prev(RecipeI)->dump();
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#endif
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return false;
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}
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RecipeI++;
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}
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return true;
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}
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static bool verifyVPBasicBlock(const VPBasicBlock *VPBB,
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const VPDominatorTree &VPDT) {
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if (!verifyPhiRecipes(VPBB))
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return false;
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// Verify that defs in VPBB dominate all their uses. The current
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// implementation is still incomplete.
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DenseMap<const VPRecipeBase *, unsigned> RecipeNumbering;
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unsigned Cnt = 0;
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for (const VPRecipeBase &R : *VPBB)
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RecipeNumbering[&R] = Cnt++;
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for (const VPRecipeBase &R : *VPBB) {
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for (const VPValue *V : R.definedValues()) {
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for (const VPUser *U : V->users()) {
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auto *UI = dyn_cast<VPRecipeBase>(U);
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// TODO: check dominance of incoming values for phis properly.
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if (!UI ||
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isa<VPHeaderPHIRecipe, VPWidenPHIRecipe, VPPredInstPHIRecipe>(UI))
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continue;
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// If the user is in the same block, check it comes after R in the
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// block.
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if (UI->getParent() == VPBB) {
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if (RecipeNumbering[UI] < RecipeNumbering[&R]) {
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errs() << "Use before def!\n";
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return false;
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}
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continue;
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}
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if (!VPDT.dominates(VPBB, UI->getParent())) {
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errs() << "Use before def!\n";
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return false;
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}
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}
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}
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}
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return true;
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}
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/// Utility function that checks whether \p VPBlockVec has duplicate
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/// VPBlockBases.
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static bool hasDuplicates(const SmallVectorImpl<VPBlockBase *> &VPBlockVec) {
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SmallDenseSet<const VPBlockBase *, 8> VPBlockSet;
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for (const auto *Block : VPBlockVec) {
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if (VPBlockSet.count(Block))
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return true;
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VPBlockSet.insert(Block);
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}
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return false;
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}
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static bool verifyBlock(const VPBlockBase *VPB, const VPDominatorTree &VPDT) {
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auto *VPBB = dyn_cast<VPBasicBlock>(VPB);
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// Check block's condition bit.
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if (VPB->getNumSuccessors() > 1 ||
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(VPBB && VPBB->getParent() && VPBB->isExiting() &&
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!VPBB->getParent()->isReplicator())) {
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if (!VPBB || !VPBB->getTerminator()) {
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errs() << "Block has multiple successors but doesn't "
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"have a proper branch recipe!\n";
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return false;
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}
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} else {
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if (VPBB && VPBB->getTerminator()) {
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errs() << "Unexpected branch recipe!\n";
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return false;
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}
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}
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// Check block's successors.
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const auto &Successors = VPB->getSuccessors();
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// There must be only one instance of a successor in block's successor list.
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// TODO: This won't work for switch statements.
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if (hasDuplicates(Successors)) {
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errs() << "Multiple instances of the same successor.\n";
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return false;
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}
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for (const VPBlockBase *Succ : Successors) {
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// There must be a bi-directional link between block and successor.
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const auto &SuccPreds = Succ->getPredecessors();
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if (!is_contained(SuccPreds, VPB)) {
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errs() << "Missing predecessor link.\n";
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return false;
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}
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}
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// Check block's predecessors.
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const auto &Predecessors = VPB->getPredecessors();
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// There must be only one instance of a predecessor in block's predecessor
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// list.
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// TODO: This won't work for switch statements.
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if (hasDuplicates(Predecessors)) {
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errs() << "Multiple instances of the same predecessor.\n";
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return false;
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}
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for (const VPBlockBase *Pred : Predecessors) {
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// Block and predecessor must be inside the same region.
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if (Pred->getParent() != VPB->getParent()) {
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errs() << "Predecessor is not in the same region.\n";
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return false;
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}
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// There must be a bi-directional link between block and predecessor.
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const auto &PredSuccs = Pred->getSuccessors();
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if (!is_contained(PredSuccs, VPB)) {
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errs() << "Missing successor link.\n";
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return false;
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}
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}
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return !VPBB || verifyVPBasicBlock(VPBB, VPDT);
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}
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/// Helper function that verifies the CFG invariants of the VPBlockBases within
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/// \p Region. Checks in this function are generic for VPBlockBases. They are
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/// not specific for VPBasicBlocks or VPRegionBlocks.
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static bool verifyBlocksInRegion(const VPRegionBlock *Region,
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const VPDominatorTree &VPDT) {
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for (const VPBlockBase *VPB : vp_depth_first_shallow(Region->getEntry())) {
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// Check block's parent.
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if (VPB->getParent() != Region) {
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errs() << "VPBlockBase has wrong parent\n";
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return false;
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}
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if (!verifyBlock(VPB, VPDT))
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return false;
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}
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return true;
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}
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/// Verify the CFG invariants of VPRegionBlock \p Region and its nested
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/// VPBlockBases. Do not recurse inside nested VPRegionBlocks.
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static bool verifyRegion(const VPRegionBlock *Region,
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const VPDominatorTree &VPDT) {
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const VPBlockBase *Entry = Region->getEntry();
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const VPBlockBase *Exiting = Region->getExiting();
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// Entry and Exiting shouldn't have any predecessor/successor, respectively.
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if (Entry->getNumPredecessors() != 0) {
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errs() << "region entry block has predecessors\n";
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return false;
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}
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if (Exiting->getNumSuccessors() != 0) {
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errs() << "region exiting block has successors\n";
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return false;
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}
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return verifyBlocksInRegion(Region, VPDT);
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}
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/// Verify the CFG invariants of VPRegionBlock \p Region and its nested
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/// VPBlockBases. Recurse inside nested VPRegionBlocks.
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static bool verifyRegionRec(const VPRegionBlock *Region,
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const VPDominatorTree &VPDT) {
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// Recurse inside nested regions and check all blocks inside the region.
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return verifyRegion(Region, VPDT) &&
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all_of(vp_depth_first_shallow(Region->getEntry()),
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[&VPDT](const VPBlockBase *VPB) {
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const auto *SubRegion = dyn_cast<VPRegionBlock>(VPB);
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return !SubRegion || verifyRegionRec(SubRegion, VPDT);
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});
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}
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bool llvm::verifyVPlanIsValid(const VPlan &Plan) {
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VPDominatorTree VPDT;
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VPDT.recalculate(const_cast<VPlan &>(Plan));
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if (any_of(
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vp_depth_first_shallow(Plan.getEntry()),
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[&VPDT](const VPBlockBase *VPB) { return !verifyBlock(VPB, VPDT); }))
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return false;
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const VPRegionBlock *TopRegion = Plan.getVectorLoopRegion();
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if (!verifyRegionRec(TopRegion, VPDT))
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return false;
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if (TopRegion->getParent()) {
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errs() << "VPlan Top Region should have no parent.\n";
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return false;
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}
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const VPBasicBlock *Entry = dyn_cast<VPBasicBlock>(TopRegion->getEntry());
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if (!Entry) {
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errs() << "VPlan entry block is not a VPBasicBlock\n";
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return false;
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}
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if (!isa<VPCanonicalIVPHIRecipe>(&*Entry->begin())) {
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errs() << "VPlan vector loop header does not start with a "
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"VPCanonicalIVPHIRecipe\n";
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return false;
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}
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const VPBasicBlock *Exiting = dyn_cast<VPBasicBlock>(TopRegion->getExiting());
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if (!Exiting) {
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errs() << "VPlan exiting block is not a VPBasicBlock\n";
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return false;
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}
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if (Exiting->empty()) {
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errs() << "VPlan vector loop exiting block must end with BranchOnCount or "
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"BranchOnCond VPInstruction but is empty\n";
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return false;
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}
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auto *LastInst = dyn_cast<VPInstruction>(std::prev(Exiting->end()));
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if (!LastInst || (LastInst->getOpcode() != VPInstruction::BranchOnCount &&
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LastInst->getOpcode() != VPInstruction::BranchOnCond)) {
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errs() << "VPlan vector loop exit must end with BranchOnCount or "
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"BranchOnCond VPInstruction\n";
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return false;
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}
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for (const auto &KV : Plan.getLiveOuts())
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if (KV.second->getNumOperands() != 1) {
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errs() << "live outs must have a single operand\n";
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return false;
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}
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return true;
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}
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