1//===- LoopTransformWarning.cpp - ----------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// Emit warnings if forced code transformations have not been performed.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/Transforms/Scalar/WarnMissedTransforms.h"
14#include "llvm/Analysis/LoopInfo.h"
15#include "llvm/Analysis/OptimizationRemarkEmitter.h"
16#include "llvm/Transforms/Utils/LoopUtils.h"
17
18using namespace llvm;
19
20#define DEBUG_TYPE "transform-warning"
21
22/// Emit warnings for forced (i.e. user-defined) loop transformations which have
23/// still not been performed.
24static void warnAboutLeftoverTransformations(Loop *L,
25 OptimizationRemarkEmitter *ORE) {
26 if (hasUnrollTransformation(L) == TM_ForcedByUser) {
27 LLVM_DEBUG(dbgs() << "Leftover unroll transformation\n");
28 ORE->emit(
29 OptDiag: DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
30 "FailedRequestedUnrolling",
31 L->getStartLoc(), L->getHeader())
32 << "loop not unrolled: the optimizer was unable to perform the "
33 "requested transformation; the transformation might be disabled or "
34 "specified as part of an unsupported transformation ordering");
35 }
36
37 if (hasUnrollAndJamTransformation(L) == TM_ForcedByUser) {
38 LLVM_DEBUG(dbgs() << "Leftover unroll-and-jam transformation\n");
39 ORE->emit(
40 OptDiag: DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
41 "FailedRequestedUnrollAndJamming",
42 L->getStartLoc(), L->getHeader())
43 << "loop not unroll-and-jammed: the optimizer was unable to perform "
44 "the requested transformation; the transformation might be disabled "
45 "or specified as part of an unsupported transformation ordering");
46 }
47
48 if (hasVectorizeTransformation(L) == TM_ForcedByUser) {
49 LLVM_DEBUG(dbgs() << "Leftover vectorization transformation\n");
50 std::optional<ElementCount> VectorizeWidth =
51 getOptionalElementCountLoopAttribute(TheLoop: L);
52 std::optional<int> InterleaveCount =
53 getOptionalIntLoopAttribute(TheLoop: L, Name: "llvm.loop.interleave.count");
54
55 if (!VectorizeWidth || VectorizeWidth->isVector())
56 ORE->emit(
57 OptDiag: DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
58 "FailedRequestedVectorization",
59 L->getStartLoc(), L->getHeader())
60 << "loop not vectorized: the optimizer was unable to perform the "
61 "requested transformation; the transformation might be disabled "
62 "or specified as part of an unsupported transformation ordering");
63 else if (InterleaveCount.value_or(u: 0) != 1)
64 ORE->emit(
65 OptDiag: DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
66 "FailedRequestedInterleaving",
67 L->getStartLoc(), L->getHeader())
68 << "loop not interleaved: the optimizer was unable to perform the "
69 "requested transformation; the transformation might be disabled "
70 "or specified as part of an unsupported transformation ordering");
71 }
72
73 if (hasDistributeTransformation(L) == TM_ForcedByUser) {
74 LLVM_DEBUG(dbgs() << "Leftover distribute transformation\n");
75 ORE->emit(
76 OptDiag: DiagnosticInfoOptimizationFailure(DEBUG_TYPE,
77 "FailedRequestedDistribution",
78 L->getStartLoc(), L->getHeader())
79 << "loop not distributed: the optimizer was unable to perform the "
80 "requested transformation; the transformation might be disabled or "
81 "specified as part of an unsupported transformation ordering");
82 }
83}
84
85static void warnAboutLeftoverTransformations(Function *F, LoopInfo *LI,
86 OptimizationRemarkEmitter *ORE) {
87 for (auto *L : LI->getLoopsInPreorder())
88 warnAboutLeftoverTransformations(L, ORE);
89}
90
91// New pass manager boilerplate
92PreservedAnalyses
93WarnMissedTransformationsPass::run(Function &F, FunctionAnalysisManager &AM) {
94 // Do not warn about not applied transformations if optimizations are
95 // disabled.
96 if (F.hasOptNone())
97 return PreservedAnalyses::all();
98
99 auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(IR&: F);
100 auto &LI = AM.getResult<LoopAnalysis>(IR&: F);
101
102 warnAboutLeftoverTransformations(F: &F, LI: &LI, ORE: &ORE);
103
104 return PreservedAnalyses::all();
105}
106