[llvm] 1db2fb9 - Revert "[ADCE] Preserve MemorySSA if only debug instructions are removed"

[Mikael Holmen via llvm-commits]

Author: Mikael Holmen
Date: 2023-03-08T07:34:12+01:00
New Revision: 1db2fb991e7b32950b4141e85d58d541cdc3dd7c

URL: https://github.com/llvm/llvm-project/commit/1db2fb991e7b32950b4141e85d58d541cdc3dd7c
DIFF: https://github.com/llvm/llvm-project/commit/1db2fb991e7b32950b4141e85d58d541cdc3dd7c.diff

LOG: Revert "[ADCE] Preserve MemorySSA if only debug instructions are removed"

This reverts commit db7d8678bcdc440ffd0529f0d970cf10cbcbe984.

Added: 
    

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

Removed: 
    llvm/test/Transforms/ADCE/preserve-memoryssa-if-only-remove-debug.ll


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/ADCE.cpp b/llvm/lib/Transforms/Scalar/ADCE.cpp
index ec07c5341d18d..d03a5033f403c 100644
--- a/llvm/lib/Transforms/Scalar/ADCE.cpp
+++ b/llvm/lib/Transforms/Scalar/ADCE.cpp
@@ -26,7 +26,6 @@
 #include "llvm/Analysis/DomTreeUpdater.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/IteratedDominanceFrontier.h"
-#include "llvm/Analysis/MemorySSA.h"
 #include "llvm/Analysis/PostDominators.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/CFG.h"
@@ -116,7 +115,6 @@ struct BlockInfoType {
 
 struct ADCEChanged {
   bool ChangedAnything = false;
-  bool ChangedNonDebugInstr = false;
   bool ChangedControlFlow = false;
 };
 
@@ -562,8 +560,6 @@ ADCEChanged AggressiveDeadCodeElimination::removeDeadInstructions() {
         continue;
 
       // Fallthrough and drop the intrinsic.
-    } else {
-      Changed.ChangedNonDebugInstr = true;
     }
 
     // Prepare to delete.
@@ -717,17 +713,8 @@ PreservedAnalyses ADCEPass::run(Function &F, FunctionAnalysisManager &FAM) {
     return PreservedAnalyses::all();
 
   PreservedAnalyses PA;
-  if (!Changed.ChangedControlFlow) {
+  if (!Changed.ChangedControlFlow)
     PA.preserveSet<CFGAnalyses>();
-    if (!Changed.ChangedNonDebugInstr) {
-      // Only removing debug instructions does not affect MemorySSA.
-      //
-      // Therefore we preserve MemorySSA when only removing debug instructions
-      // since otherwise later passes may behave 
diff erently which then makes
-      // the presence of debug info affect code generation.
-      PA.preserve<MemorySSAAnalysis>();
-    }
-  }
   PA.preserve<DominatorTreeAnalysis>();
   PA.preserve<PostDominatorTreeAnalysis>();
 

diff  --git a/llvm/test/Transforms/ADCE/preserve-memoryssa-if-only-remove-debug.ll b/llvm/test/Transforms/ADCE/preserve-memoryssa-if-only-remove-debug.ll
deleted file mode 100644
index 339bc758344f9..0000000000000
--- a/llvm/test/Transforms/ADCE/preserve-memoryssa-if-only-remove-debug.ll
+++ /dev/null
@@ -1,70 +0,0 @@
-; RUN: opt -passes='require<memoryssa>,adce' -o - -S -debug-pass-manager < %s 2>&1 | FileCheck %s
-
-; ADCE should remove the dbg.declare in test1, but it should preserve
-; MemorySSA since it only removed a debug instruction.
-
-; Invalidating MemorySSA when only removing debug instructions may lead
-; to 
diff erent code with/without debug info present.
-; In
-;  https://github.com/llvm/llvm-project/issues/58285
-; we saw how ADCE removed a dbg.declare, invalidated all analyses, and later
-; DSE behaved in some way. Without the dbg.declare in the input ADCE kept
-; analysis info, and DSE behaved 
diff erently.
-
-; CHECK: Running analysis: MemorySSAAnalysis on test1
-; CHECK: Running pass: ADCEPass on test1 (1 instruction)
-; CHECK-NOT: Invalidating analysis: MemorySSAAnalysis on test1
-
-; In test2 ADCE also removes an instruction, but since we remove a non-debug
-; instruction as well we invalidate several analyses, including MemorySSA.
-
-; CHECK: Running analysis: MemorySSAAnalysis on test2
-; CHECK: Running pass: ADCEPass on test2 (2 instructions)
-; CHECK: Invalidating analysis: MemorySSAAnalysis on test2
-; CHECK: Running pass: PrintModulePass
-
-; CHECK-LABEL: @test1(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    ret i16 0
-
-; CHECK-LABEL: @test2(
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    ret i16 0
-
-define i16 @test1() {
-entry:
-  call void @llvm.dbg.declare(metadata ptr undef, metadata !4, metadata !DIExpression()), !dbg !16
-  ret i16 0
-}
-
-define i16 @test2() {
-entry:
-  %dead = add i16 1, 2
-  ret i16 0
-}
-
-; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
-declare void @llvm.dbg.declare(metadata, metadata, metadata) #0
-
-attributes #0 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
-
-!llvm.dbg.cu = !{}
-!llvm.module.flags = !{!0, !1, !2, !3}
-
-!0 = !{i32 7, !"Dwarf Version", i32 4}
-!1 = !{i32 2, !"Debug Info Version", i32 3}
-!2 = !{i32 1, !"wchar_size", i32 1}
-!3 = !{i32 7, !"frame-pointer", i32 2}
-!4 = !DILocalVariable(name: "w", scope: !5, file: !6, line: 18, type: !11)
-!5 = distinct !DILexicalBlock(scope: !7, file: !6, line: 18, column: 8)
-!6 = !DIFile(filename: "foo2.c", directory: "/llvm")
-!7 = distinct !DISubprogram(name: "test1", scope: !6, file: !6, line: 14, type: !8, scopeLine: 14, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !10)
-!8 = !DISubroutineType(types: !9)
-!9 = !{}
-!10 = distinct !DICompileUnit(language: DW_LANG_C99, file: !6, producer: "clang version 16.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !9, splitDebugInlining: false, nameTableKind: None)
-!11 = !DIDerivedType(tag: DW_TAG_typedef, name: "uint64_t", file: !12, line: 60, baseType: !13)
-!12 = !DIFile(filename: "/include/sys/_stdint.h", directory: "")
-!13 = !DIDerivedType(tag: DW_TAG_typedef, name: "__uint64_t", file: !14, line: 108, baseType: !15)
-!14 = !DIFile(filename: "/include/machine/_default_types.h", directory: "")
-!15 = !DIBasicType(name: "unsigned long long", size: 64, encoding: DW_ATE_unsigned)
-!16 = !DILocation(line: 18, column: 8, scope: !5)
\ No newline at end of file