[llvm] a61c0ad - [DebugInfo][LSR] Limit the size of SCEV translated to DIExpression
Chris Jackson via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 7 08:38:41 PDT 2021
Author: Chris Jackson
Date: 2021-10-07T15:38:28Z
New Revision: a61c0adba1944ef0792ecb4e5aa75072a240d5da
URL: https://github.com/llvm/llvm-project/commit/a61c0adba1944ef0792ecb4e5aa75072a240d5da
DIFF: https://github.com/llvm/llvm-project/commit/a61c0adba1944ef0792ecb4e5aa75072a240d5da.diff
LOG: [DebugInfo][LSR] Limit the size of SCEV translated to DIExpression
SCEV-based salvaging will use excessive resources if it encounters
very long SCEV expressions. This patch places a limit on the length of
SCEV expression that salvaging will attempt to translate.
Reviewed by: Orlando
Differential Revision: https://reviews.llvm.org/D110558
Added:
llvm/test/Transforms/LoopStrengthReduce/pr51656.ll
Modified:
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 3a37be1bf7e72..784a2bdfd98cc 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -136,6 +136,12 @@ using namespace llvm;
/// worst cases before LSR burns too much compile time and stack space.
static const unsigned MaxIVUsers = 200;
+/// Limit the size of expression that SCEV-based salvaging will attempt to
+/// translate into a DIExpression.
+/// Choose a maximum size such that debuginfo is not excessively increased and
+/// the salvaging is not too expensive for the compiler.
+static const unsigned MaxSCEVSalvageExpressionSize = 64;
+
// Temporary flag to cleanup congruent phis after LSR phi expansion.
// It's currently disabled until we can determine whether it's truly useful or
// not. The flag should be removed after the v3.0 release.
@@ -6152,6 +6158,9 @@ static void RewriteDVIUsingIterCount(DVIRecoveryRec CachedDVI,
if (!Rec->isAffine())
return;
+ if (CachedDVI.SCEV->getExpressionSize() > MaxSCEVSalvageExpressionSize)
+ return;
+
// Initialise a new builder with the iteration count expression. In
// combination with the value's SCEV this enables recovery.
SCEVDbgValueBuilder RecoverValue(IterationCount);
@@ -6196,7 +6205,10 @@ DbgRewriteSalvageableDVIs(llvm::Loop *L, ScalarEvolution &SE,
if (!IVAddRec->isAffine())
return;
- // The iteratioun count is required to recover location values.
+ if (IVAddRec->getExpressionSize() > MaxSCEVSalvageExpressionSize)
+ return;
+
+ // The iteration count is required to recover location values.
SCEVDbgValueBuilder IterCountExpr;
IterCountExpr.pushValue(LSRInductionVar);
if (!IterCountExpr.SCEVToIterCountExpr(*IVAddRec, SE))
diff --git a/llvm/test/Transforms/LoopStrengthReduce/pr51656.ll b/llvm/test/Transforms/LoopStrengthReduce/pr51656.ll
new file mode 100644
index 0000000000000..8a8a111b76e39
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/pr51656.ll
@@ -0,0 +1,142 @@
+; RUN: opt -loop-reduce -S %s | FileCheck %s
+
+;; This test ensures that no attempt is made to translate long SCEVs into
+;; DIExpressions. Attempting the translation can use excessive resources and
+;; result in crashes.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+ at c = dso_local local_unnamed_addr global i32 0, align 4, !dbg !0
+ at b = dso_local local_unnamed_addr global i32 0, align 4, !dbg !9
+ at a = dso_local local_unnamed_addr global i32 0, align 4, !dbg !5
+
+define dso_local i32 @d() local_unnamed_addr #0 !dbg !16 {
+entry:
+ %b.promoted = load i32, i32* @b, align 4, !tbaa !29
+ %mul = mul nsw i32 %b.promoted, %b.promoted, !dbg !33
+ %mul.1 = mul nsw i32 %mul, %mul, !dbg !33
+ %mul.2 = mul nsw i32 %mul.1, %mul.1, !dbg !33
+ %mul.3 = mul nsw i32 %mul.2, %mul.2, !dbg !33
+ %mul.4 = mul nsw i32 %mul.3, %mul.3, !dbg !33
+ %mul.5 = mul nsw i32 %mul.4, %mul.4, !dbg !33
+ %mul.6 = mul nsw i32 %mul.5, %mul.5, !dbg !33
+ %mul.7 = mul nsw i32 %mul.6, %mul.6, !dbg !33
+ %mul.8 = mul nsw i32 %mul.7, %mul.7, !dbg !33
+ %mul.9 = mul nsw i32 %mul.8, %mul.8, !dbg !33
+ %mul.10 = mul nsw i32 %mul.9, %mul.9, !dbg !33
+ %mul.11 = mul nsw i32 %mul.10, %mul.10, !dbg !33
+ %mul.12 = mul nsw i32 %mul.11, %mul.11, !dbg !33
+ %mul.13 = mul nsw i32 %mul.12, %mul.12, !dbg !33
+ %mul.14 = mul nsw i32 %mul.13, %mul.13, !dbg !33
+ %mul.15 = mul nsw i32 %mul.14, %mul.14, !dbg !33
+ %mul.16 = mul nsw i32 %mul.15, %mul.15, !dbg !33
+ %mul.17 = mul nsw i32 %mul.16, %mul.16, !dbg !33
+ %mul.18 = mul nsw i32 %mul.17, %mul.17, !dbg !33
+ %mul.19 = mul nsw i32 %mul.18, %mul.18, !dbg !33
+ %mul.20 = mul nsw i32 %mul.19, %mul.19, !dbg !33
+ %mul.21 = mul nsw i32 %mul.20, %mul.20, !dbg !33
+ %mul.22 = mul nsw i32 %mul.21, %mul.21, !dbg !33
+ %mul.23 = mul nsw i32 %mul.22, %mul.22, !dbg !33
+ %mul.24 = mul nsw i32 %mul.23, %mul.23, !dbg !33
+ %mul.25 = mul nsw i32 %mul.24, %mul.24, !dbg !33
+ %mul.26 = mul nsw i32 %mul.25, %mul.25, !dbg !33
+ %mul.27 = mul nsw i32 %mul.26, %mul.26, !dbg !33
+ %mul.28 = mul nsw i32 %mul.27, %mul.27, !dbg !33
+ %mul.29 = mul nsw i32 %mul.28, %mul.28, !dbg !33
+ %mul.30 = mul nsw i32 %mul.29, %mul.29, !dbg !33
+ %mul.31 = mul nsw i32 %mul.30, %mul.30, !dbg !33
+ %mul.32 = mul nsw i32 %mul.31, %mul.31, !dbg !33
+ %mul.33 = mul nsw i32 %mul.32, %mul.32, !dbg !33
+ %mul.34 = mul nsw i32 %mul.33, %mul.33, !dbg !33
+ %mul.35 = mul nsw i32 %mul.34, %mul.34, !dbg !33
+ %mul.36 = mul nsw i32 %mul.35, %mul.35, !dbg !33
+ %mul.37 = mul nsw i32 %mul.36, %mul.36, !dbg !33
+ %mul.38 = mul nsw i32 %mul.37, %mul.37, !dbg !33
+ %mul.39 = mul nsw i32 %mul.38, %mul.38, !dbg !33
+ %mul.40 = mul nsw i32 %mul.39, %mul.39, !dbg !33
+ %mul.41 = mul nsw i32 %mul.40, %mul.40, !dbg !33
+ %mul.42 = mul nsw i32 %mul.41, %mul.41, !dbg !33
+ %mul.43 = mul nsw i32 %mul.42, %mul.42, !dbg !33
+ %mul.44 = mul nsw i32 %mul.43, %mul.43, !dbg !33
+ %mul.45 = mul nsw i32 %mul.44, %mul.44, !dbg !33
+ %mul.46 = mul nsw i32 %mul.45, %mul.45, !dbg !33
+ %mul.47 = mul nsw i32 %mul.46, %mul.46, !dbg !33
+ store i32 49, i32* @c, align 4, !dbg !36, !tbaa !29
+ store i32 %mul.47, i32* @b, align 4, !dbg !37, !tbaa !29
+ %.pr = load i32, i32* @a, align 4, !dbg !38, !tbaa !29
+ %tobool.not8 = icmp eq i32 %.pr, 0, !dbg !39
+ br i1 %tobool.not8, label %for.end3, label %for.body2.preheader, !dbg !39
+
+for.body2.preheader: ; preds = %entry
+ br label %for.body2, !dbg !39
+
+for.body2: ; preds = %for.body2.preheader, %for.body2
+ %0 = phi i32 [ %sub, %for.body2 ], [ %.pr, %for.body2.preheader ]
+ %sub = sub nsw i32 %0, %mul.47, !dbg !40
+ ; CHECK: call void @llvm.dbg.value(metadata !DIArgList(i32 undef, i32 %mul.47), metadata ![[VAR_e:[0-9]+]], metadata !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_minus, DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_LLVM_convert, 64, DW_ATE_signed, DW_OP_stack_value))
+ call void @llvm.dbg.value(metadata i32 %sub, metadata !20, metadata !DIExpression(DW_OP_LLVM_convert, 32, DW_ATE_signed, DW_OP_LLVM_convert, 64, DW_ATE_signed, DW_OP_stack_value)), !dbg !41
+ %tobool.not = icmp eq i32 %sub, 0, !dbg !39
+ br i1 %tobool.not, label %for.cond1.for.end3_crit_edge, label %for.body2, !dbg !39, !llvm.loop !42
+
+for.cond1.for.end3_crit_edge: ; preds = %for.body2
+ store i32 0, i32* @a, align 4, !dbg !40, !tbaa !29
+ br label %for.end3, !dbg !39
+
+for.end3: ; preds = %for.cond1.for.end3_crit_edge, %entry
+ ret i32 undef, !dbg !45
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!11, !12, !13, !14}
+!llvm.ident = !{!15}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "c", scope: !2, file: !7, line: 2, type: !8, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 14.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "test.c", directory: "/test")
+!4 = !{!5, !9, !0}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !7, line: 2, type: !8, isLocal: false, isDefinition: true)
+!7 = !DIFile(filename: "./test.c", directory: "/test")
+!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!9 = !DIGlobalVariableExpression(var: !10, expr: !DIExpression())
+!10 = distinct !DIGlobalVariable(name: "b", scope: !2, file: !7, line: 2, type: !8, isLocal: false, isDefinition: true)
+!11 = !{i32 7, !"Dwarf Version", i32 4}
+!12 = !{i32 2, !"Debug Info Version", i32 3}
+!13 = !{i32 1, !"wchar_size", i32 4}
+!14 = !{i32 7, !"uwtable", i32 1}
+!15 = !{!"clang version 14.0.0"}
+!16 = distinct !DISubprogram(name: "d", scope: !7, file: !7, line: 3, type: !17, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !19)
+!17 = !DISubroutineType(types: !18)
+!18 = !{!8}
+!19 = !{!20}
+; CHECK: ![[VAR_e]] = !DILocalVariable(name: "e", scope: !21, file: !7, line: 8, type: !24)
+!20 = !DILocalVariable(name: "e", scope: !21, file: !7, line: 8, type: !24)
+!21 = distinct !DILexicalBlock(scope: !22, file: !7, line: 7, column: 14)
+!22 = distinct !DILexicalBlock(scope: !23, file: !7, line: 7, column: 3)
+!23 = distinct !DILexicalBlock(scope: !16, file: !7, line: 7, column: 3)
+!24 = !DIDerivedType(tag: DW_TAG_typedef, name: "uint64_t", file: !25, line: 27, baseType: !26)
+!25 = !DIFile(filename: "/usr/include/x86_64-linux-gnu/bits/stdint-uintn.h", directory: "")
+!26 = !DIDerivedType(tag: DW_TAG_typedef, name: "__uint64_t", file: !27, line: 44, baseType: !28)
+!27 = !DIFile(filename: "/usr/include/x86_64-linux-gnu/bits/types.h", directory: "")
+!28 = !DIBasicType(name: "long unsigned int", size: 64, encoding: DW_ATE_unsigned)
+!29 = !{!30, !30, i64 0}
+!30 = !{!"int", !31, i64 0}
+!31 = !{!"omnipotent char", !32, i64 0}
+!32 = !{!"Simple C/C++ TBAA"}
+!33 = !DILocation(line: 6, column: 7, scope: !34)
+!34 = distinct !DILexicalBlock(scope: !35, file: !7, line: 5, column: 3)
+!35 = distinct !DILexicalBlock(scope: !16, file: !7, line: 5, column: 3)
+!36 = !DILocation(line: 0, scope: !16)
+!37 = !DILocation(line: 0, scope: !34)
+!38 = !DILocation(line: 7, column: 10, scope: !22)
+!39 = !DILocation(line: 7, column: 3, scope: !23)
+!40 = !DILocation(line: 8, column: 20, scope: !21)
+!41 = !DILocation(line: 0, scope: !21)
+!42 = distinct !{!42, !39, !43, !44}
+!43 = !DILocation(line: 9, column: 3, scope: !23)
+!44 = !{!"llvm.loop.mustprogress"}
+!45 = !DILocation(line: 10, column: 1, scope: !16)
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