[llvm] [indvars] Missing variables at Og: (PR #69920)
Carlos Alberto Enciso via llvm-commits
llvm-commits at lists.llvm.org
Wed Jan 3 04:11:34 PST 2024
https://github.com/CarlosAlbertoEnciso updated https://github.com/llvm/llvm-project/pull/69920
>From 9cad349af5d4cce724ce8213227849833221b2a8 Mon Sep 17 00:00:00 2001
From: Carlos Alberto Enciso <carlos.alberto.enciso at gmail.com>
Date: Wed, 3 Jan 2024 12:03:42 +0000
Subject: [PATCH] [indvars] Missing variables at Og:
https://bugs.llvm.org/show_bug.cgi?id=51735
https://github.com/llvm/llvm-project/issues/51077
In the given test case:
4 ...
5 void bar() {
6 int End = 777;
7 int Index = 27;
8 char Var = 1;
9 for (; Index < End; ++Index)
10 ;
11 nop();
12 }
13 ...
Missing local variable 'Index' after loop 'Induction Variable Elimination'.
When adding a breakpoint at line 11, LLDB does not have information on
the variable. But it has info on 'Var' and 'End'.
Address reviewers comments.
- Early exit to simplify the logic.
- Avoid inserting the same instruction in multiple blocks.
- Skip debug-users with variadic variable locations.
- Change some comments to improve readability.
- Add code to clone and move the debug value.
- Modify second test case to include multiple exit blocks.
---
.../include/llvm/Transforms/Utils/LoopUtils.h | 4 +
llvm/lib/Transforms/Utils/LoopUtils.cpp | 57 +++++++++
.../test/Transforms/LoopSimplify/pr51735-1.ll | 118 ++++++++++++++++++
llvm/test/Transforms/LoopSimplify/pr51735.ll | 84 +++++++++++++
4 files changed, 263 insertions(+)
create mode 100644 llvm/test/Transforms/LoopSimplify/pr51735-1.ll
create mode 100644 llvm/test/Transforms/LoopSimplify/pr51735.ll
diff --git a/llvm/include/llvm/Transforms/Utils/LoopUtils.h b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
index 5a1385d01d8e44..26230fe97f6786 100644
--- a/llvm/include/llvm/Transforms/Utils/LoopUtils.h
+++ b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
@@ -468,6 +468,10 @@ int rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
ReplaceExitVal ReplaceExitValue,
SmallVector<WeakTrackingVH, 16> &DeadInsts);
+/// Assign exit values to variables that use this loop variable during the loop.
+void addDebugValuesToLoopVariable(Loop *L, ScalarEvolution *SE, PHINode *PN);
+void addDebugValuesToLoopVariable(Loop *L, Value *ExitValue, PHINode *PN);
+
/// Set weights for \p UnrolledLoop and \p RemainderLoop based on weights for
/// \p OrigLoop and the following distribution of \p OrigLoop iteration among \p
/// UnrolledLoop and \p RemainderLoop. \p UnrolledLoop receives weights that
diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 59485126b280ab..5109666500c3f9 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -31,6 +31,7 @@
#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/IR/DIBuilder.h"
+#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
@@ -1341,6 +1342,36 @@ static bool checkIsIndPhi(PHINode *Phi, Loop *L, ScalarEvolution *SE,
return InductionDescriptor::isInductionPHI(Phi, L, SE, ID);
}
+void llvm::addDebugValuesToLoopVariable(Loop *L, Value *ExitValue,
+ PHINode *PN) {
+ SmallVector<BasicBlock *> ExitBlocks;
+ L->getExitBlocks(ExitBlocks);
+ SmallVector<DbgVariableIntrinsic *> DbgUsers;
+ findDbgUsers(DbgUsers, PN);
+ for (auto *DebugUser : DbgUsers) {
+ // Skip debug-users with variadic variable locations; they will not,
+ // get updated, which is fine as that is the existing behaviour.
+ if (DebugUser->hasArgList())
+ continue;
+ for (BasicBlock *Exit : ExitBlocks) {
+ auto *Cloned = cast<DbgVariableIntrinsic>(DebugUser->clone());
+ Cloned->replaceVariableLocationOp(0u, ExitValue);
+ Cloned->insertBefore(Exit->getFirstNonPHI());
+ }
+ }
+}
+
+void llvm::addDebugValuesToLoopVariable(Loop *L, ScalarEvolution *SE,
+ PHINode *PN) {
+ if (!PN)
+ return;
+ const SCEV *PNSCEV = SE->getSCEVAtScope(PN, L->getParentLoop());
+ if (auto *Const = dyn_cast<SCEVConstant>(PNSCEV)) {
+ Value *FinalIVValue = Const->getValue();
+ addDebugValuesToLoopVariable(L, FinalIVValue, PN);
+ }
+}
+
int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
ScalarEvolution *SE,
const TargetTransformInfo *TTI,
@@ -1482,6 +1513,21 @@ int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
(isa<PHINode>(Inst) || isa<LandingPadInst>(Inst)) ?
&*Inst->getParent()->getFirstInsertionPt() : Inst;
RewritePhiSet.emplace_back(PN, i, ExitValue, InsertPt, HighCost);
+
+ // Add debug values if the PN is a induction variable.
+ PHINode *IndVar = L->getInductionVariable(*SE);
+ for (Value *V : PN->incoming_values())
+ if (V == IndVar) {
+ if (BasicBlock *Successor = ExitBB->getSingleSuccessor()) {
+ SmallVector<DbgVariableIntrinsic *> DbgUsers;
+ findDbgUsers(DbgUsers, V);
+ for (auto *DebugUser : DbgUsers) {
+ auto *Cloned = cast<DbgVariableIntrinsic>(DebugUser->clone());
+ Cloned->replaceVariableLocationOp(0u, PN);
+ Cloned->insertBefore(Successor->getFirstNonPHI());
+ }
+ }
+ }
}
}
}
@@ -1540,11 +1586,22 @@ int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
// Replace PN with ExitVal if that is legal and does not break LCSSA.
if (PN->getNumIncomingValues() == 1 &&
LI->replacementPreservesLCSSAForm(PN, ExitVal)) {
+ addDebugValuesToLoopVariable(L, ExitVal, PN);
PN->replaceAllUsesWith(ExitVal);
PN->eraseFromParent();
}
}
+ // If there are no PHIs to be rewritten then there are no loop live-out
+ // values, try to rewrite variables corresponding to the induction variable
+ // with their constant exit-values if we computed any. Otherwise debug-info
+ // will completely forget that this loop happened.
+ if (RewritePhiSet.empty()) {
+ // The loop exit value has been updated; insert the debug location
+ // for the given the induction variable with its final value.
+ addDebugValuesToLoopVariable(L, SE, L->getInductionVariable(*SE));
+ }
+
// The insertion point instruction may have been deleted; clear it out
// so that the rewriter doesn't trip over it later.
Rewriter.clearInsertPoint();
diff --git a/llvm/test/Transforms/LoopSimplify/pr51735-1.ll b/llvm/test/Transforms/LoopSimplify/pr51735-1.ll
new file mode 100644
index 00000000000000..293553b000c13c
--- /dev/null
+++ b/llvm/test/Transforms/LoopSimplify/pr51735-1.ll
@@ -0,0 +1,118 @@
+; RUN: opt -passes=indvars -S -o - < %s | FileCheck %s
+
+; Make sure that when we delete the loop, that the variable Index has
+; the 777 value.
+
+; CHECK: for.cond:
+; CHECK: call void @llvm.dbg.value(metadata i32 %Index.0, metadata ![[DBG:[0-9]+]], {{.*}}
+
+; CHECK: for.extra:
+; CHECK: %call.0 = call noundef i32 @"?nop@@YAHH at Z"(i32 noundef %Index.0), {{.*}}
+; CHECK: br i1 %cmp.0, label %for.cond, label %if.else, {{.*}}
+
+; CHECK: if.then:
+; CHECK: call void @llvm.dbg.value(metadata i32 777, metadata ![[DBG]], {{.*}}
+; CHECK: br label %for.end, {{.*}}
+
+; CHECK: if.else:
+; CHECK: call void @llvm.dbg.value(metadata i32 777, metadata ![[DBG]], {{.*}}
+; CHECK: br label %for.end, {{.*}}
+
+; CHECK: for.end:
+; CHECK: call void @llvm.dbg.value(metadata i32 777, metadata ![[DBG]], {{.*}}
+
+; CHECK-DAG: ![[DBG]] = !DILocalVariable(name: "Index"{{.*}})
+
+define dso_local noundef i32 @"?nop@@YAHH at Z"(i32 noundef %Param) !dbg !11 {
+entry:
+ %Param.addr = alloca i32, align 4
+ store i32 %Param, ptr %Param.addr, align 4
+ call void @llvm.dbg.declare(metadata ptr %Param.addr, metadata !32, metadata !DIExpression()), !dbg !35
+ ret i32 0, !dbg !36
+}
+
+define dso_local void @_Z3barv() local_unnamed_addr #1 !dbg !12 {
+entry:
+ call void @llvm.dbg.value(metadata i32 777, metadata !16, metadata !DIExpression()), !dbg !17
+ call void @llvm.dbg.value(metadata i32 27, metadata !18, metadata !DIExpression()), !dbg !17
+ call void @llvm.dbg.value(metadata i32 1, metadata !19, metadata !DIExpression()), !dbg !17
+ call void @llvm.dbg.value(metadata i32 1, metadata !30, metadata !DIExpression()), !dbg !17
+ br label %for.cond, !dbg !20
+
+for.cond: ; preds = %for.cond, %entry
+ %Index.0 = phi i32 [ 27, %entry ], [ %inc, %for.extra ], !dbg !17
+ call void @llvm.dbg.value(metadata i32 %Index.0, metadata !18, metadata !DIExpression()), !dbg !17
+ %cmp = icmp ult i32 %Index.0, 777, !dbg !21
+ %inc = add nuw nsw i32 %Index.0, 1, !dbg !24
+ call void @llvm.dbg.value(metadata i32 %inc, metadata !18, metadata !DIExpression()), !dbg !17
+ br i1 %cmp, label %for.extra, label %if.then, !dbg !25, !llvm.loop !26
+
+for.extra:
+ %call.0 = call noundef i32 @"?nop@@YAHH at Z"(i32 noundef %Index.0), !dbg !21
+ %cmp.0 = icmp ult i32 %Index.0, %call.0, !dbg !21
+ br i1 %cmp.0, label %for.cond, label %if.else, !dbg !25, !llvm.loop !26
+
+if.then: ; preds = %for.cond
+ %Var.1 = add nsw i32 %Index.0, 1, !dbg !20
+ call void @llvm.dbg.value(metadata i32 %Var.1, metadata !19, metadata !DIExpression()), !dbg !20
+ br label %for.end, !dbg !20
+
+if.else:
+ %Var.2 = add nsw i32 %Index.0, 2, !dbg !20
+ call void @llvm.dbg.value(metadata i32 %Var.2, metadata !19, metadata !DIExpression()), !dbg !20
+ br label %for.end, !dbg !20
+
+for.end: ; preds = %if.else, %if.then
+ %Zeta.0 = phi i32 [ %Var.1, %if.then ], [ %Var.2, %if.else ], !dbg !20
+ call void @llvm.dbg.value(metadata i32 %Zeta.0, metadata !30, metadata !DIExpression()), !dbg !20
+ %Var.3 = add nsw i32 %Index.0, 1, !dbg !20
+ call void @llvm.dbg.value(metadata i32 %Var.3, metadata !19, metadata !DIExpression()), !dbg !20
+ %call = call noundef i32 @"?nop@@YAHH at Z"(i32 noundef %Index.0), !dbg !37
+ ret void, !dbg !29
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+declare void @llvm.dbg.declare(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_C_plus_plus_14, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.cpp", 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, !"frame-pointer", i32 2}
+!9 = !{!"clang version 18.0.0"}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = distinct !DISubprogram(name: "nop", linkageName: "?nop@@YAHH at Z", scope: !1, file: !1, line: 1, type: !33, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !31)
+!12 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !1, file: !1, line: 5, type: !13, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !15)
+!13 = !DISubroutineType(types: !14)
+!14 = !{null}
+!15 = !{}
+!16 = !DILocalVariable(name: "End", scope: !12, file: !1, line: 6, type: !10)
+!17 = !DILocation(line: 0, scope: !12)
+!18 = !DILocalVariable(name: "Index", scope: !12, file: !1, line: 7, type: !10)
+!19 = !DILocalVariable(name: "Var", scope: !12, file: !1, line: 8, type: !10)
+!20 = !DILocation(line: 9, column: 3, scope: !12)
+!21 = !DILocation(line: 9, column: 16, scope: !22)
+!22 = distinct !DILexicalBlock(scope: !23, file: !1, line: 9, column: 3)
+!23 = distinct !DILexicalBlock(scope: !12, file: !1, line: 9, column: 3)
+!24 = !DILocation(line: 9, column: 23, scope: !22)
+!25 = !DILocation(line: 9, column: 3, scope: !23)
+!26 = distinct !{!26, !25, !27, !28}
+!27 = !DILocation(line: 10, column: 5, scope: !23)
+!28 = !{!"llvm.loop.mustprogress"}
+!29 = !DILocation(line: 12, column: 1, scope: !12)
+!30 = !DILocalVariable(name: "Zeta", scope: !12, file: !1, line: 8, type: !10)
+!31 = !{!32}
+!32 = !DILocalVariable(name: "Param", arg: 1, scope: !11, file: !1, line: 1, type: !10)
+!33 = !DISubroutineType(types: !34)
+!34 = !{!10, !10}
+!35 = !DILocation(line: 1, scope: !11)
+!36 = !DILocation(line: 2, scope: !11)
+!37 = !DILocation(line: 20, scope: !12)
diff --git a/llvm/test/Transforms/LoopSimplify/pr51735.ll b/llvm/test/Transforms/LoopSimplify/pr51735.ll
new file mode 100644
index 00000000000000..50221128ca04b6
--- /dev/null
+++ b/llvm/test/Transforms/LoopSimplify/pr51735.ll
@@ -0,0 +1,84 @@
+; RUN: opt -passes=indvars -S -o - < %s | FileCheck %s
+
+; Make sure that when we delete the loop in the code below, that the variable
+; Index has the 777 value.
+
+; 1 __attribute__((optnone)) int nop() {
+; 2 return 0;
+; 3 }
+; 4
+; 5 void bar() {
+; 6 int End = 777;
+; 7 int Index = 27;
+; 8 char Var = 1;
+; 9 for (; Index < End; ++Index)
+; 10 ;
+; 11 nop();
+; 12 }
+; 13
+; 14 int main () {
+; 15 bar();
+; 16 }
+
+; CHECK: for.cond:
+; CHECK: call void @llvm.dbg.value(metadata i32 poison, metadata ![[DBG:[0-9]+]], {{.*}}
+; CHECK: call void @llvm.dbg.value(metadata i32 poison, metadata ![[DBG]], {{.*}}
+; CHECK: br i1 false, label %for.cond, label %for.end, {{.*}}
+; CHECK: for.end:
+; CHECK: call void @llvm.dbg.value(metadata i32 777, metadata ![[DBG]], {{.*}}
+; CHECK-DAG: ![[DBG]] = !DILocalVariable(name: "Index"{{.*}})
+
+define dso_local void @_Z3barv() local_unnamed_addr #1 !dbg !15 {
+entry:
+ call void @llvm.dbg.value(metadata i32 777, metadata !19, metadata !DIExpression()), !dbg !20
+ call void @llvm.dbg.value(metadata i32 27, metadata !21, metadata !DIExpression()), !dbg !20
+ call void @llvm.dbg.value(metadata i32 1, metadata !22, metadata !DIExpression()), !dbg !20
+ br label %for.cond, !dbg !23
+
+for.cond: ; preds = %for.cond, %entry
+ %Index.0 = phi i32 [ 27, %entry ], [ %inc, %for.cond ], !dbg !20
+ call void @llvm.dbg.value(metadata i32 %Index.0, metadata !21, metadata !DIExpression()), !dbg !20
+ %cmp = icmp ult i32 %Index.0, 777, !dbg !24
+ %inc = add nuw nsw i32 %Index.0, 1, !dbg !27
+ call void @llvm.dbg.value(metadata i32 %inc, metadata !21, metadata !DIExpression()), !dbg !20
+ br i1 %cmp, label %for.cond, label %for.end, !dbg !28, !llvm.loop !29
+
+for.end: ; preds = %for.cond
+ ret void, !dbg !33
+}
+
+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_C_plus_plus_14, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.cpp", 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, !"frame-pointer", i32 2}
+!9 = !{!"clang version 18.0.0"}
+!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !1, file: !1, line: 5, type: !16, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !18)
+!16 = !DISubroutineType(types: !17)
+!17 = !{null}
+!18 = !{}
+!19 = !DILocalVariable(name: "End", scope: !15, file: !1, line: 6, type: !13)
+!20 = !DILocation(line: 0, scope: !15)
+!21 = !DILocalVariable(name: "Index", scope: !15, file: !1, line: 7, type: !13)
+!22 = !DILocalVariable(name: "Var", scope: !15, file: !1, line: 8, type: !13)
+!23 = !DILocation(line: 9, column: 3, scope: !15)
+!24 = !DILocation(line: 9, column: 16, scope: !25)
+!25 = distinct !DILexicalBlock(scope: !26, file: !1, line: 9, column: 3)
+!26 = distinct !DILexicalBlock(scope: !15, file: !1, line: 9, column: 3)
+!27 = !DILocation(line: 9, column: 23, scope: !25)
+!28 = !DILocation(line: 9, column: 3, scope: !26)
+!29 = distinct !{!29, !28, !30, !31}
+!30 = !DILocation(line: 10, column: 5, scope: !26)
+!31 = !{!"llvm.loop.mustprogress"}
+!33 = !DILocation(line: 12, column: 1, scope: !15)
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