[llvm] r344120 - [DebugInfo][Dexter] Unreachable line stepped onto after SimplifyCFG.
Carlos Alberto Enciso via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 10 01:29:55 PDT 2018
Author: carlos.alberto.enciso
Date: Wed Oct 10 01:29:55 2018
New Revision: 344120
URL: http://llvm.org/viewvc/llvm-project?rev=344120&view=rev
Log:
[DebugInfo][Dexter] Unreachable line stepped onto after SimplifyCFG.
When SimplifyCFG changes the PHI node into a select instruction, the debug line records becomes ambiguous. It causes the debugger to display unreachable source lines.
Differential Revision: https://reviews.llvm.org/D52887
Added:
llvm/trunk/test/CodeGen/X86/pr38762.ll
Modified:
llvm/trunk/include/llvm/Transforms/Utils/Local.h
llvm/trunk/lib/Transforms/Utils/Local.cpp
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/CodeGen/X86/pr38763.ll
Modified: llvm/trunk/include/llvm/Transforms/Utils/Local.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/Local.h?rev=344120&r1=344119&r2=344120&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/Local.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/Local.h Wed Oct 10 01:29:55 2018
@@ -446,6 +446,15 @@ void copyRangeMetadata(const DataLayout
/// Remove the debug intrinsic instructions for the given instruction.
void dropDebugUsers(Instruction &I);
+/// Hoist all of the instructions in the \p IfBlock to the dominant block
+/// \p DomBlock, by moving its instructions to the insertion point \p InsertPt.
+///
+/// The moved instructions receive the insertion point debug location values
+/// (DILocations) and their debug intrinsic instructions (dbg.values) are
+/// removed.
+void hoistAllInstructionsInto(BasicBlock *DomBlock,Instruction *InsertPt,
+ BasicBlock *IfBlock);
+
//===----------------------------------------------------------------------===//
// Intrinsic pattern matching
//
Modified: llvm/trunk/lib/Transforms/Utils/Local.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Local.cpp?rev=344120&r1=344119&r2=344120&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/Local.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/Local.cpp Wed Oct 10 01:29:55 2018
@@ -2529,6 +2529,34 @@ void llvm::dropDebugUsers(Instruction &I
DII->eraseFromParent();
}
+void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock,Instruction *InsertPt,
+ BasicBlock *IfBlock) {
+ // Since we are moving the instructions out of its basic block, we do not
+ // retain their original debug locations (DILocations) and debug intrinsic
+ // instructions (dbg.values).
+ //
+ // Doing so would degrade the debugging experience and adversely affect the
+ // accuracy of profiling information.
+ //
+ // Currently, when hoisting the instructions, we take the following actions:
+ // - Remove their dbg.values.
+ // - Set their debug locations to the values from the insertion point.
+ //
+ // See PR38762 for more details.
+ //
+ // TODO: Extend llvm.dbg.value to take more than one SSA Value (PR39141) to
+ // encode predicated DIExpressions that yield different results on different
+ // code paths.
+ for (auto &I : *IfBlock) {
+ I.dropUnknownNonDebugMetadata();
+ dropDebugUsers(I);
+ I.setDebugLoc(InsertPt->getDebugLoc());
+ }
+ DomBlock->getInstList().splice(InsertPt->getIterator(),
+ IfBlock->getInstList(), IfBlock->begin(),
+ IfBlock->getTerminator()->getIterator());
+}
+
namespace {
/// A potential constituent of a bitreverse or bswap expression. See
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=344120&r1=344119&r2=344120&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Wed Oct 10 01:29:55 2018
@@ -2375,24 +2375,10 @@ static bool FoldTwoEntryPHINode(PHINode
// Move all 'aggressive' instructions, which are defined in the
// conditional parts of the if's up to the dominating block.
- if (IfBlock1) {
- for (auto &I : *IfBlock1) {
- I.dropUnknownNonDebugMetadata();
- dropDebugUsers(I);
- }
- DomBlock->getInstList().splice(InsertPt->getIterator(),
- IfBlock1->getInstList(), IfBlock1->begin(),
- IfBlock1->getTerminator()->getIterator());
- }
- if (IfBlock2) {
- for (auto &I : *IfBlock2) {
- I.dropUnknownNonDebugMetadata();
- dropDebugUsers(I);
- }
- DomBlock->getInstList().splice(InsertPt->getIterator(),
- IfBlock2->getInstList(), IfBlock2->begin(),
- IfBlock2->getTerminator()->getIterator());
- }
+ if (IfBlock1)
+ hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock1);
+ if (IfBlock2)
+ hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock2);
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
// Change the PHI node into a select instruction.
Added: llvm/trunk/test/CodeGen/X86/pr38762.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr38762.ll?rev=344120&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr38762.ll (added)
+++ llvm/trunk/test/CodeGen/X86/pr38762.ll Wed Oct 10 01:29:55 2018
@@ -0,0 +1,101 @@
+; RUN: opt < %s -S -simplifycfg | FileCheck %s
+
+; Note: This patch is a complement to pr38763.
+;
+; When SimplifyCFG changes the PHI node into a select instruction, the debug
+; information becomes ambiguous. It causes the debugger to display unreached
+; lines and invalid variable values.
+;
+; When in the debugger, on the line "if (read1 > 3)", and we step from the
+; 'if' condition, onto the addition, then back to the 'if' again, which is
+; misleading because that addition doesn't really "happen" (it's speculated).
+
+; IR generated with:
+; clang -S -g -gno-column-info -O2 -emit-llvm pr38762.cpp -o pr38762.ll -mllvm -opt-bisect-limit=10
+
+; // pr38762.cpp
+; int main() {
+; volatile int foo = 0;
+; int read1 = foo;
+; int brains = foo;
+;
+; if (read1 > 3) {
+; brains *= 2;
+; brains += 1;
+; }
+;
+; return brains;
+; }
+
+; Change the debug locations associated with the PHI nodes being promoted, to
+; the debug locations from the insertion point in the dominant block.
+
+; CHECK-LABEL: entry
+; CHECK: %cmp = icmp sgt i32 %foo.0., 3, !dbg !14
+; CHECK: %mul = shl nsw i32 %foo.0.5, 1, !dbg !16
+; CHECK-NOT: call void @llvm.dbg.value(metadata i32 %mul, metadata !15, metadata !DIExpression()), !dbg !25
+; CHECK: %add = or i32 %mul, 1, !dbg !16
+; CHECK-NOT: call void @llvm.dbg.value(metadata i32 %add, metadata !15, metadata !DIExpression()), !dbg !25
+; CHECK: %brains.0 = select i1 %cmp, i32 %add, i32 %foo.0.5, !dbg !16
+
+; ModuleID = 'pr38762.cpp'
+source_filename = "pr38762.cpp"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux-gnu"
+
+; Function Attrs: norecurse nounwind uwtable
+define dso_local i32 @main() local_unnamed_addr #0 !dbg !7 {
+entry:
+ %foo = alloca i32, align 4
+ %foo.0..sroa_cast = bitcast i32* %foo to i8*
+ store volatile i32 0, i32* %foo, align 4
+ %foo.0. = load volatile i32, i32* %foo, align 4
+ %foo.0.5 = load volatile i32, i32* %foo, align 4
+ call void @llvm.dbg.value(metadata i32 %foo.0.5, metadata !15, metadata !DIExpression()), !dbg !25
+ %cmp = icmp sgt i32 %foo.0., 3, !dbg !26
+ br i1 %cmp, label %if.then, label %if.end, !dbg !28
+
+if.then: ; preds = %entry
+ %mul = shl nsw i32 %foo.0.5, 1, !dbg !29
+ call void @llvm.dbg.value(metadata i32 %mul, metadata !15, metadata !DIExpression()), !dbg !25
+ %add = or i32 %mul, 1, !dbg !31
+ call void @llvm.dbg.value(metadata i32 %add, metadata !15, metadata !DIExpression()), !dbg !25
+ br label %if.end, !dbg !32
+
+if.end: ; preds = %if.then, %entry
+ %brains.0 = phi i32 [ %add, %if.then ], [ %foo.0.5, %entry ], !dbg !33
+ call void @llvm.dbg.value(metadata i32 %brains.0, metadata !15, metadata !DIExpression()), !dbg !25
+ ret i32 %brains.0, !dbg !35
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 8.0.0 (trunk 343753)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "pr38762.cpp", directory: ".")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 8.0.0 (trunk 343753)"}
+!7 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !11)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !{!15}
+!13 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !10)
+!15 = !DILocalVariable(name: "brains", scope: !7, file: !1, line: 4, type: !10)
+!25 = !DILocation(line: 4, scope: !7)
+!26 = !DILocation(line: 6, scope: !27)
+!27 = distinct !DILexicalBlock(scope: !7, file: !1, line: 6)
+!28 = !DILocation(line: 6, scope: !7)
+!29 = !DILocation(line: 7, scope: !30)
+!30 = distinct !DILexicalBlock(scope: !27, file: !1, line: 6)
+!31 = !DILocation(line: 8, scope: !30)
+!32 = !DILocation(line: 9, scope: !30)
+!33 = !DILocation(line: 0, scope: !7)
+!34 = !DILocation(line: 12, scope: !7)
+!35 = !DILocation(line: 11, scope: !7)
Modified: llvm/trunk/test/CodeGen/X86/pr38763.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr38763.ll?rev=344120&r1=344119&r2=344120&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr38763.ll (original)
+++ llvm/trunk/test/CodeGen/X86/pr38763.ll Wed Oct 10 01:29:55 2018
@@ -30,13 +30,13 @@
; branches, as they becomes ambiguous.
; CHECK-LABEL: entry
-; CHECK: %cmp = icmp eq i32 %foo.0., 4
-; CHECK: %add = add nsw i32 %foo.0.4, 2, !dbg !18
+; CHECK: %cmp = icmp eq i32 %foo.0., 4, !dbg !14
+; CHECK: %add = add nsw i32 %foo.0.4, 2, !dbg !16
; CHECK-NOT: @llvm.dbg.value(metadata i32 %add
-; CHECK: %sub = add nsw i32 %foo.0.4, -2, !dbg !21
+; CHECK: %sub = add nsw i32 %foo.0.4, -2, !dbg !16
; CHECK-NOT: @llvm.dbg.value(metadata i32 %sub
; CHECK: %result.0 = select i1 %cmp, i32 %add, i32 %sub
-; CHECK: call void @llvm.dbg.value(metadata i32 %result.0, metadata !12, metadata !DIExpression()), !dbg !17
+; CHECK: call void @llvm.dbg.value(metadata i32 %result.0, metadata !12, metadata !DIExpression()), !dbg !13
; ModuleID = 'pr38763.cpp'
source_filename = "pr38763.cpp"
@@ -48,12 +48,12 @@ define dso_local i32 @main() local_unnam
entry:
%foo = alloca i32, align 4
%foo.0..sroa_cast = bitcast i32* %foo to i8*
- store volatile i32 4, i32* %foo, align 4, !tbaa !19
+ store volatile i32 4, i32* %foo, align 4
%foo.0. = load volatile i32, i32* %foo, align 4
%foo.0.4 = load volatile i32, i32* %foo, align 4
call void @llvm.dbg.value(metadata i32 0, metadata !16, metadata !DIExpression()), !dbg !27
- %cmp = icmp eq i32 %foo.0., 4
- br i1 %cmp, label %if.then, label %if.else
+ %cmp = icmp eq i32 %foo.0., 4, !dbg !28
+ br i1 %cmp, label %if.then, label %if.else, !dbg !30
if.then: ; preds = %entry
%add = add nsw i32 %foo.0.4, 2, !dbg !31
@@ -91,12 +91,10 @@ declare void @llvm.dbg.value(metadata, m
!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!11 = !{!16}
!16 = !DILocalVariable(name: "result", scope: !7, file: !1, line: 6, type: !10)
-!19 = !{!20, !20, i64 0}
-!20 = !{!"int", !21, i64 0}
-!21 = !{!"omnipotent char", !22, i64 0}
-!22 = !{!"Simple C++ TBAA"}
!27 = !DILocation(line: 6, column: 7, scope: !7)
+!28 = !DILocation(line: 7, column: 12, scope: !29)
!29 = distinct !DILexicalBlock(scope: !7, file: !1, line: 7, column: 7)
+!30 = !DILocation(line: 7, column: 7, scope: !7)
!31 = !DILocation(line: 8, column: 20, scope: !32)
!32 = distinct !DILexicalBlock(scope: !29, file: !1, line: 7, column: 18)
!34 = !DILocation(line: 10, column: 20, scope: !35)
More information about the llvm-commits
mailing list