[llvm] 98562e8 - [Assignment Tracking][19/*] Account for assignment tracking in ADCE

[via llvm-commits]

Author: OCHyams
Date: 2022-11-15T13:13:38Z
New Revision: 98562e8bb712bb8bcfedb8795156bbbdf6609c66

URL: https://github.com/llvm/llvm-project/commit/98562e8bb712bb8bcfedb8795156bbbdf6609c66
DIFF: https://github.com/llvm/llvm-project/commit/98562e8bb712bb8bcfedb8795156bbbdf6609c66.diff

LOG: [Assignment Tracking][19/*] Account for assignment tracking in ADCE

The Assignment Tracking debug-info feature is outlined in this RFC:

https://discourse.llvm.org/t/
rfc-assignment-tracking-a-better-way-of-specifying-variable-locations-in-ir

In an attempt to preserve more info, don't delete dbg.assign intrinsics that
are considered "out of scope" if they're linked to instructions.

Reviewed By: jmorse

Differential Revision: https://reviews.llvm.org/D133314

Added: 
    llvm/test/DebugInfo/Generic/assignment-tracking/adce/no-delete.ll

Modified: 
    llvm/lib/Transforms/Scalar/ADCE.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/ADCE.cpp b/llvm/lib/Transforms/Scalar/ADCE.cpp
index 92289bbcfb0a..253293582945 100644
--- a/llvm/lib/Transforms/Scalar/ADCE.cpp
+++ b/llvm/lib/Transforms/Scalar/ADCE.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Analysis/PostDominators.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/CFG.h"
+#include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/Dominators.h"
@@ -543,6 +544,11 @@ bool AggressiveDeadCodeElimination::removeDeadInstructions() {
       continue;
 
     if (auto *DII = dyn_cast<DbgInfoIntrinsic>(&I)) {
+      // Avoid removing a dbg.assign that is linked to instructions because it
+      // holds information about an existing store.
+      if (auto *DAI = dyn_cast<DbgAssignIntrinsic>(DII))
+        if (!at::getAssignmentInsts(DAI).empty())
+          continue;
       // Check if the scope of this variable location is alive.
       if (AliveScopes.count(DII->getDebugLoc()->getScope()))
         continue;

diff  --git a/llvm/test/DebugInfo/Generic/assignment-tracking/adce/no-delete.ll b/llvm/test/DebugInfo/Generic/assignment-tracking/adce/no-delete.ll
new file mode 100644
index 000000000000..9782882a3f7e
--- /dev/null
+++ b/llvm/test/DebugInfo/Generic/assignment-tracking/adce/no-delete.ll
@@ -0,0 +1,48 @@
+; RUN: opt %s -passes=adce -experimental-assignment-tracking -S -o - \
+; RUN: | FileCheck %s
+
+;; $ cat test.c
+;; void fun(int local) {}
+;;
+;; $ clang test.c -g -O1 -Xclang -disable-llvm-passes | opt -S -passes=declare-to-assign
+
+;; Check that the dbg.assign intrinsics that are considered "out of scope" (dbg
+;; attachments have been deleted) but still linked to an instruction are not
+;; deleted by ADCE.
+
+; CHECK: llvm.dbg.assign
+; CHECK: llvm.dbg.assign
+
+define dso_local void @fun(i32 noundef %local) #0 !dbg !7 {
+entry:
+  %local.addr = alloca i32, align 4, !DIAssignID !13
+  call void @llvm.dbg.assign(metadata i1 undef, metadata !12, metadata !DIExpression(), metadata !13, metadata ptr %local.addr, metadata !DIExpression()), !dbg !14
+  store i32 %local, ptr %local.addr, align 4, !DIAssignID !19
+  call void @llvm.dbg.assign(metadata i32 %local, metadata !12, metadata !DIExpression(), metadata !19, metadata ptr %local.addr, metadata !DIExpression()), !dbg !14
+  ret void
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 14.0.0", 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 7, !"uwtable", i32 1}
+!6 = !{!"clang version 14.0.0"}
+!7 = distinct !DISubprogram(name: "fun", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !{!12}
+!12 = !DILocalVariable(name: "local", arg: 1, scope: !7, file: !1, line: 1, type: !10)
+!13 = distinct !DIAssignID()
+!14 = !DILocation(line: 0, scope: !7)
+!19 = distinct !DIAssignID()
+!20 = !DILocation(line: 1, column: 22, scope: !7)