[llvm] [AssignemntTracking] Skip large types in redundant debug info pruning (PR #74329)
Orlando Cazalet-Hyams via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 4 07:22:32 PST 2023
https://github.com/OCHyams created https://github.com/llvm/llvm-project/pull/74329
The pruning code uses a BitVector for varibles. BitVector supports sizes less than
`max(uint32)-63`, so skip equal and larger types. Fixes https://github.com/llvm/llvm-project/issues/74189 (crash report).
The reason it's `max(uint32)-63` and not `max(uint32)` is because of `BitVector::NumBitWords`:
```
unsigned NumBitWords(unsigned S) const {
return (S + BITWORD_SIZE-1) / BITWORD_SIZE;
}
```
The numerator evaluation yields an incorrect value when S + BITWORD_SIZE wraps to >= 1. I'm hesitant to change BitVector code, so have gone with this defensive fix.
>From 6d84bba1d6770690c31b8166769f0e932cc2105f Mon Sep 17 00:00:00 2001
From: OCHyams <orlando.hyams at sony.com>
Date: Mon, 4 Dec 2023 12:08:08 +0000
Subject: [PATCH 1/3] [AssignemntTracking] Skip large types in redundant debug
info pruning
The pruning code uses a BitVector for varibles. BitVector supports sizes up to
max(uint32), so skip larger types. Fixes #74189 (crash report).
---
.../CodeGen/AssignmentTrackingAnalysis.cpp | 4 +-
.../assignment-tracking/X86/large-type.ll | 49 +++++++++++++++++++
2 files changed, 52 insertions(+), 1 deletion(-)
create mode 100644 llvm/test/DebugInfo/assignment-tracking/X86/large-type.ll
diff --git a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
index f00528023c91d..ab43d4f497a77 100644
--- a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
+++ b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
@@ -2296,8 +2296,10 @@ removeRedundantDbgLocsUsingBackwardScan(const BasicBlock *BB,
getAggregate(FnVarLocs.getVariable(RIt->VariableID));
uint64_t SizeInBits = Aggr.first->getSizeInBits().value_or(0);
- if (SizeInBits == 0) {
+ if (SizeInBits == 0 || SizeInBits > std::numeric_limits<uint32_t>::max()) {
// If the size is unknown (0) then keep this location def to be safe.
+ // Do the same for defs of very large variables, which can't be
+ // represented with a BitVector.
NewDefsReversed.push_back(*RIt);
continue;
}
diff --git a/llvm/test/DebugInfo/assignment-tracking/X86/large-type.ll b/llvm/test/DebugInfo/assignment-tracking/X86/large-type.ll
new file mode 100644
index 0000000000000..c07bfb380477e
--- /dev/null
+++ b/llvm/test/DebugInfo/assignment-tracking/X86/large-type.ll
@@ -0,0 +1,49 @@
+; RUN: llc %s -stop-after=finalize-isel -o - \
+; RUN: | FileCheck %s --implicit-check-not=DBG_
+
+;; Generated from C source:
+;; int main () {
+;; char a1[__INT_MAX__];
+;; a1[__INT_MAX__ - 1] = 5;
+;; return a1[__INT_MAX__ - 1];
+;; }
+;;
+;; Check obscenely large types don't cause a crash.
+; CHECK: DBG_VALUE 5, $noreg, ![[#]], !DIExpression(DW_OP_LLVM_fragment, 4294967280, 8)
+
+define dso_local i32 @main() local_unnamed_addr !dbg !10 {
+entry:
+;; FIXME: SROA currently creates incorrect fragments if bit_offset > max(u32),
+;; with and without assignment-tracking.
+ tail call void @llvm.dbg.value(metadata i8 5, metadata !15, metadata !DIExpression(DW_OP_LLVM_fragment, 4294967280, 8)), !dbg !20
+ ret i32 5, !dbg !21
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5, !6, !7, !8}
+!llvm.ident = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 18.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.c", directory: "/")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 8, !"PIC Level", i32 2}
+!6 = !{i32 7, !"PIE Level", i32 2}
+!7 = !{i32 7, !"uwtable", i32 2}
+!8 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
+!9 = !{!"clang version 18.0.0"}
+!10 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 3, type: !11, scopeLine: 4, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !14)
+!11 = !DISubroutineType(types: !12)
+!12 = !{!13}
+!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!14 = !{!15}
+!15 = !DILocalVariable(name: "a1", scope: !10, file: !1, line: 5, type: !16)
+!16 = !DICompositeType(tag: DW_TAG_array_type, baseType: !17, size: 17179869176, elements: !18)
+!17 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+!18 = !{!19}
+!19 = !DISubrange(count: 2147483647)
+!20 = !DILocation(line: 0, scope: !10)
+!21 = !DILocation(line: 7, column: 3, scope: !10)
>From ca1a6c76989af649f7252b675ecfb241976c71d7 Mon Sep 17 00:00:00 2001
From: OCHyams <orlando.hyams at sony.com>
Date: Mon, 4 Dec 2023 15:09:04 +0000
Subject: [PATCH 2/3] fix edge case
---
llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp | 3 ++-
.../DebugInfo/assignment-tracking/X86/large-type.ll | 11 ++++++++++-
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
index ab43d4f497a77..5632b37adc41f 100644
--- a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
+++ b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
@@ -2296,7 +2296,8 @@ removeRedundantDbgLocsUsingBackwardScan(const BasicBlock *BB,
getAggregate(FnVarLocs.getVariable(RIt->VariableID));
uint64_t SizeInBits = Aggr.first->getSizeInBits().value_or(0);
- if (SizeInBits == 0 || SizeInBits > std::numeric_limits<uint32_t>::max()) {
+ const uint64_t MaxSize = std::numeric_limits<unsigned>::max() - 64;
+ if (SizeInBits == 0 || SizeInBits >= MaxSize) {
// If the size is unknown (0) then keep this location def to be safe.
// Do the same for defs of very large variables, which can't be
// represented with a BitVector.
diff --git a/llvm/test/DebugInfo/assignment-tracking/X86/large-type.ll b/llvm/test/DebugInfo/assignment-tracking/X86/large-type.ll
index c07bfb380477e..5fa7ead58574d 100644
--- a/llvm/test/DebugInfo/assignment-tracking/X86/large-type.ll
+++ b/llvm/test/DebugInfo/assignment-tracking/X86/large-type.ll
@@ -1,7 +1,7 @@
; RUN: llc %s -stop-after=finalize-isel -o - \
; RUN: | FileCheck %s --implicit-check-not=DBG_
-;; Generated from C source:
+;; Based on optimized IR from C source:
;; int main () {
;; char a1[__INT_MAX__];
;; a1[__INT_MAX__ - 1] = 5;
@@ -10,12 +10,17 @@
;;
;; Check obscenely large types don't cause a crash.
; CHECK: DBG_VALUE 5, $noreg, ![[#]], !DIExpression(DW_OP_LLVM_fragment, 4294967280, 8)
+; CHECK: DBG_VALUE 6, $noreg, ![[#]], !DIExpression(DW_OP_LLVM_fragment, 0, 8)
+; CHECK: DBG_VALUE 7, $noreg, ![[#]], !DIExpression(DW_OP_LLVM_fragment, 0, 8)
define dso_local i32 @main() local_unnamed_addr !dbg !10 {
entry:
;; FIXME: SROA currently creates incorrect fragments if bit_offset > max(u32),
;; with and without assignment-tracking.
tail call void @llvm.dbg.value(metadata i8 5, metadata !15, metadata !DIExpression(DW_OP_LLVM_fragment, 4294967280, 8)), !dbg !20
+;; These two were inserted by hand.
+ tail call void @llvm.dbg.value(metadata i8 6, metadata !22, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !20
+ tail call void @llvm.dbg.value(metadata i8 7, metadata !23, metadata !DIExpression(DW_OP_LLVM_fragment, 0, 8)), !dbg !20
ret i32 5, !dbg !21
}
@@ -47,3 +52,7 @@ declare void @llvm.dbg.value(metadata, metadata, metadata)
!19 = !DISubrange(count: 2147483647)
!20 = !DILocation(line: 0, scope: !10)
!21 = !DILocation(line: 7, column: 3, scope: !10)
+!22 = !DILocalVariable(name: "a2", scope: !10, file: !1, line: 5, type: !16)
+!23 = !DILocalVariable(name: "a3", scope: !10, file: !1, line: 5, type: !16)
+!24 = !DICompositeType(tag: DW_TAG_array_type, baseType: !17, size: 4294967232, elements: !18)
+!25 = !DICompositeType(tag: DW_TAG_array_type, baseType: !17, size: 4294967233, elements: !18)
>From 989bdf6efd638bc2df8f43d2c4cb88a489ae2d9c Mon Sep 17 00:00:00 2001
From: OCHyams <orlando.hyams at sony.com>
Date: Mon, 4 Dec 2023 15:18:38 +0000
Subject: [PATCH 3/3] actually fix edge case
---
llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
index 5632b37adc41f..2349fadb1ea6d 100644
--- a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
+++ b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
@@ -2296,8 +2296,8 @@ removeRedundantDbgLocsUsingBackwardScan(const BasicBlock *BB,
getAggregate(FnVarLocs.getVariable(RIt->VariableID));
uint64_t SizeInBits = Aggr.first->getSizeInBits().value_or(0);
- const uint64_t MaxSize = std::numeric_limits<unsigned>::max() - 64;
- if (SizeInBits == 0 || SizeInBits >= MaxSize) {
+ const uint64_t MaxSize = std::numeric_limits<unsigned>::max() - 63;
+ if (SizeInBits == 0 || SizeInBits > MaxSize) {
// If the size is unknown (0) then keep this location def to be safe.
// Do the same for defs of very large variables, which can't be
// represented with a BitVector.
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