[Assignment Tracking][24/*] Always RemoveRedundantDbgInstrs in instco…

…mbine in assignment tracking builds

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

This reduces peak memory overhead by 15% when building CTMark's tramp3d-v4 with
-O2 -g with assignment tracking enabled.

Reviewed By: jmorse

Differential Revision: https://reviews.llvm.org/D133321

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -99,6 +99,7 @@
 #include "llvm/Support/KnownBits.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/InstCombine/InstCombine.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include <algorithm>
 #include <cassert>
@@ -4593,6 +4594,13 @@ static bool combineInstructionsOverFunction(
   bool MadeIRChange = false;
   if (ShouldLowerDbgDeclare)
     MadeIRChange = LowerDbgDeclare(F);
+  // LowerDbgDeclare calls RemoveRedundantDbgInstrs, but LowerDbgDeclare will
+  // almost never return true when running an assignment tracking build. Take
+  // this opportunity to do some clean up for assignment tracking builds too.
+  if (!MadeIRChange && getEnableAssignmentTracking()) {
+    for (auto &BB : F)
+      RemoveRedundantDbgInstrs(&BB);
+  }
 
   // Iterate while there is work to do.
   unsigned Iteration = 0;

llvm/test/DebugInfo/Generic/assignment-tracking/instcombine/do-not-remove-redundant-dbg.ll

@@ -0,0 +1,49 @@
+; RUN: opt -passes=instcombine -S %s -o -  \
+; RUN: | FileCheck %s --implicit-check-not="call void @llvm.dbg"
+
+;; Based on the test remove-redundant-dbg.ll.
+;;
+;; Check that instcombine does not remove redundant debug intrinsics when
+;; assignment tracking is turned off. This test is here to check the existing
+;; behaviour is maintained. If it is discovered that it is profitable to remove
+;; these intrinsics in instcombine then it's okay to remove this test.
+
+; CHECK: @llvm.dbg.value(metadata i32 undef
+; CHECK: @llvm.dbg.value(metadata i32 0
+; CHECK: @llvm.dbg.value(metadata i32 1
+
+define dso_local void @_Z3funv() local_unnamed_addr !dbg !7 {
+entry:
+  call void @llvm.dbg.value(metadata i32 undef, metadata !11, metadata !DIExpression()), !dbg !14
+  call void @_Z3extv(), !dbg !15
+  call void @llvm.dbg.value(metadata i32 0, metadata !11, metadata !DIExpression()), !dbg !14
+  call void @llvm.dbg.value(metadata i32 1, metadata !11, metadata !DIExpression()), !dbg !14
+  ret void, !dbg !16
+}
+
+declare !dbg !17 dso_local void @_Z3extv() local_unnamed_addr
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 14.0.0", isOptimized: true, 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 7, !"uwtable", i32 1}
+!6 = !{!"clang version 14.0.0)"}
+!7 = distinct !DISubprogram(name: "fun", linkageName: "_Z3funv", scope: !1, file: !1, line: 2, type: !8, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !10)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !{!11}
+!11 = !DILocalVariable(name: "a", scope: !7, file: !1, line: 2, type: !12)
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = distinct !DIAssignID()
+!14 = !DILocation(line: 0, scope: !7)
+!15 = !DILocation(line: 2, column: 25, scope: !7)
+!16 = !DILocation(line: 2, column: 32, scope: !7)
+!17 = !DISubprogram(name: "ext", linkageName: "_Z3extv", scope: !1, file: !1, line: 1, type: !8, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !18)
+!18 = !{}

llvm/test/DebugInfo/Generic/assignment-tracking/instcombine/remove-redundant-dbg.ll

@@ -0,0 +1,45 @@
+; RUN: opt -passes=instcombine -S %s -o - -experimental-assignment-tracking \
+; RUN: | FileCheck %s --implicit-check-not="call void @llvm.dbg"
+
+;; Check that instcombine removes redundant debug intrinsics. This has a
+;; significant positive impact on peak memory. CTMark's tramp3d-v4's peak
+;; memory with assignment tracking enabled is reduced by about 15% with this
+;; change.
+
+; CHECK: @llvm.dbg.assign(metadata i32 1
+
+define dso_local void @_Z3funv() local_unnamed_addr !dbg !7 {
+entry:
+   call void @llvm.dbg.assign(metadata i32 undef, metadata !11, metadata !DIExpression(), metadata !13, metadata ptr undef, metadata !DIExpression()), !dbg !14
+   call void @_Z3extv(), !dbg !15
+  call void @llvm.dbg.assign(metadata i32 0, metadata !11, metadata !DIExpression(), metadata !13, metadata ptr undef, metadata !DIExpression()), !dbg !14
+  call void @llvm.dbg.assign(metadata i32 1, metadata !11, metadata !DIExpression(), metadata !13, metadata ptr undef, metadata !DIExpression()), !dbg !14
+  ret void, !dbg !16
+}
+
+declare !dbg !17 dso_local void @_Z3extv() local_unnamed_addr
+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_C_plus_plus_14, file: !1, producer: "clang version 14.0.0", isOptimized: true, 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 7, !"uwtable", i32 1}
+!6 = !{!"clang version 14.0.0)"}
+!7 = distinct !DISubprogram(name: "fun", linkageName: "_Z3funv", scope: !1, file: !1, line: 2, type: !8, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !10)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !{!11}
+!11 = !DILocalVariable(name: "a", scope: !7, file: !1, line: 2, type: !12)
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = distinct !DIAssignID()
+!14 = !DILocation(line: 0, scope: !7)
+!15 = !DILocation(line: 2, column: 25, scope: !7)
+!16 = !DILocation(line: 2, column: 32, scope: !7)
+!17 = !DISubprogram(name: "ext", linkageName: "_Z3extv", scope: !1, file: !1, line: 1, type: !8, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !18)
+!18 = !{}

llvm/test/DebugInfo/Generic/assignment-tracking/salvage-value.ll

@@ -13,7 +13,7 @@ entry:
 ; CHECK: call void @llvm.dbg.assign(metadata i32 %x,{{.+}}metadata !DIExpression(DW_OP_plus_uconst, 1, DW_OP_stack_value),{{.+}}, metadata ptr %p, metadata !DIExpression())
 
  %add1 = add nsw i32 %x, %y, !dbg !29
- call void @llvm.dbg.assign(metadata i32 %add1, metadata !14, metadata !DIExpression(), metadata !31, metadata ptr %p, metadata !DIExpression()), !dbg !16
+ call void @llvm.dbg.assign(metadata i32 %add1, metadata !32, metadata !DIExpression(), metadata !31, metadata ptr %p, metadata !DIExpression()), !dbg !16
 ;; %add1 is not salvaged as it requires two values and DIArgList is
 ;; not (yet) supported for dbg.assigns.
 ; CHECK-NEXT: call void @llvm.dbg.assign(metadata i32 undef,{{.+}}, metadata !DIExpression(),{{.+}}, metadata ptr %p, metadata !DIExpression())
@@ -24,12 +24,12 @@ entry:
 ; CHECK-NEXT: call void @llvm.dbg.assign(metadata i32 %x,{{.+}}, metadata !DIExpression(),{{.+}}, metadata ptr %p, metadata !DIExpression())
 
   %arrayidx1 = getelementptr inbounds i32, ptr %p, i32 1
-  call void @llvm.dbg.assign(metadata i32 %x, metadata !14, metadata !DIExpression(), metadata !18, metadata ptr %arrayidx1, metadata !DIExpression()), !dbg !16
+  call void @llvm.dbg.assign(metadata i32 %x, metadata !33, metadata !DIExpression(), metadata !18, metadata ptr %arrayidx1, metadata !DIExpression()), !dbg !16
 ;; %arrayidx1 is salvaged.
 ; CHECK-NEXT: call void @llvm.dbg.assign(metadata i32 %x,{{.+}}, metadata !DIExpression(),{{.+}}, metadata ptr %p, metadata !DIExpression(DW_OP_plus_uconst, 4))
 
   %arrayidx2 = getelementptr inbounds i32, ptr %p, i32 %x
-  call void @llvm.dbg.assign(metadata i32 %x, metadata !14, metadata !DIExpression(), metadata !19, metadata ptr %arrayidx2, metadata !DIExpression()), !dbg !16
+  call void @llvm.dbg.assign(metadata i32 %x, metadata !34, metadata !DIExpression(), metadata !19, metadata ptr %arrayidx2, metadata !DIExpression()), !dbg !16
 ;; Variadic DIExpressions for dbg.assign address component is not supported -
 ;; set undef.
 ; CHECK-NEXT: call void @llvm.dbg.assign(metadata i32 %x,{{.+}}, metadata !DIExpression(),{{.+}}, metadata ptr undef, metadata !DIExpression())
@@ -67,3 +67,7 @@ declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata,
 !28 = distinct !DIAssignID()
 !29 = !DILocation(line: 4, column: 13, scope: !7)
 !31 = distinct !DIAssignID()
+!32 = !DILocalVariable(name: "Local1", scope: !7, file: !1, line: 3, type: !10)
+!33 = !DILocalVariable(name: "Local2", scope: !7, file: !1, line: 3, type: !10)
+!34 = !DILocalVariable(name: "Local3", scope: !7, file: !1, line: 3, type: !10)
+!35 = !DILocalVariable(name: "Local4", scope: !7, file: !1, line: 3, type: !10)