[DebugInfo][GlobalOpt] Preserve source locs for optimized loads (llvm#134828)

Some optimizations in globalopt simplify uses of a global value to uses
of a generated global bool value; in some cases where this happens, the
newly-generated instructions would not have the original source
location(s) of the instructions they replaced propagated to them; this
patch properly preserves those source locations.

Found using llvm#107279.

Author: SLTozer

llvm/lib/Transforms/IPO/GlobalOpt.cpp

@@ -965,11 +965,12 @@ OptimizeGlobalAddressOfAllocation(GlobalVariable *GV, CallInst *CI,
     if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
       // The global is initialized when the store to it occurs. If the stored
       // value is null value, the global bool is set to false, otherwise true.
-      new StoreInst(ConstantInt::getBool(
-                        GV->getContext(),
-                        !isa<ConstantPointerNull>(SI->getValueOperand())),
-                    InitBool, false, Align(1), SI->getOrdering(),
-                    SI->getSyncScopeID(), SI->getIterator());
+      auto *NewSI = new StoreInst(
+          ConstantInt::getBool(GV->getContext(), !isa<ConstantPointerNull>(
+                                                     SI->getValueOperand())),
+          InitBool, false, Align(1), SI->getOrdering(), SI->getSyncScopeID(),
+          SI->getIterator());
+      NewSI->setDebugLoc(SI->getDebugLoc());
       SI->eraseFromParent();
       continue;
     }
@@ -988,6 +989,11 @@ OptimizeGlobalAddressOfAllocation(GlobalVariable *GV, CallInst *CI,
                                InitBool->getName() + ".val", false, Align(1),
                                LI->getOrdering(), LI->getSyncScopeID(),
                                LI->getIterator());
+      // FIXME: Should we use the DebugLoc of the load used by the predicate, or
+      // the predicate? The load seems most appropriate, but there's an argument
+      // that the new load does not represent the old load, but is simply a
+      // component of recomputing the predicate.
+      cast<LoadInst>(LV)->setDebugLoc(LI->getDebugLoc());
       InitBoolUsed = true;
       switch (ICI->getPredicate()) {
       default: llvm_unreachable("Unknown ICmp Predicate!");
@@ -1000,6 +1006,7 @@ OptimizeGlobalAddressOfAllocation(GlobalVariable *GV, CallInst *CI,
       case ICmpInst::ICMP_ULE:
       case ICmpInst::ICMP_EQ:
         LV = BinaryOperator::CreateNot(LV, "notinit", ICI->getIterator());
+        cast<BinaryOperator>(LV)->setDebugLoc(ICI->getDebugLoc());
         break;
       case ICmpInst::ICMP_NE:
       case ICmpInst::ICMP_UGT:
@@ -1276,6 +1283,7 @@ static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
               new LoadInst(NewGV->getValueType(), NewGV, LI->getName() + ".b",
                            false, Align(1), LI->getOrdering(),
                            LI->getSyncScopeID(), LI->getIterator());
+          cast<LoadInst>(StoreVal)->setDebugLoc(LI->getDebugLoc());
         } else {
           assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
                  "This is not a form that we understand!");

llvm/test/Transforms/GlobalOpt/X86/preserve-dbgloc-of-load-store-to-bool.ll

@@ -0,0 +1,99 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -p=globalopt -S | FileCheck %s
+
+;; Test that when we are able to simplify uses of global variables with loads of
+;; newly generated bool values, we transfer debuglocs over correctly.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@global = internal global i32 0
+@global.1 = internal unnamed_addr global ptr null, align 8
+
+define void @ham() !dbg !7 {
+; CHECK-LABEL: define void @ham(
+; CHECK-SAME: ) local_unnamed_addr !dbg [[DBG4:![0-9]+]] {
+; CHECK-NEXT:  [[BB:.*:]]
+; CHECK-NEXT:    [[LOAD_B:%.*]] = load i1, ptr @global, align 1, !dbg [[DBG6:![0-9]+]]
+; CHECK-NEXT:    [[LOAD_B1:%.*]] = load i1, ptr @global, align 1, !dbg [[DBG6]]
+; CHECK-NEXT:    [[LOAD:%.*]] = zext i1 [[LOAD_B1]] to i32, !dbg [[DBG6]]
+; CHECK-NEXT:    store i1 [[LOAD_B]], ptr @global, align 1
+; CHECK-NEXT:    ret void
+;
+bb:
+  %load = load i32, ptr @global, align 4, !dbg !4
+  store i32 %load, ptr @global, align 4
+  ret void
+}
+
+define void @hoge() {
+; CHECK-LABEL: define void @hoge() local_unnamed_addr {
+; CHECK-NEXT:  [[BB:.*:]]
+; CHECK-NEXT:    store i1 true, ptr @global, align 1
+; CHECK-NEXT:    ret void
+;
+bb:
+  store i32 1, ptr @global, align 4
+  ret void
+}
+
+define void @bar() !dbg !13 {
+; CHECK-LABEL: define void @bar(
+; CHECK-SAME: ) local_unnamed_addr !dbg [[DBG8:![0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    store i1 true, ptr @global.1.init, align 1, !dbg [[DBG9:![0-9]+]]
+; CHECK-NEXT:    ret void
+;
+entry:
+  %call = tail call noalias nonnull dereferenceable(48) ptr @_Znwm(i64 48)
+  store ptr %call, ptr @global.1, align 8, !dbg !14
+  ret void
+}
+
+define void @pluto() !dbg !10 {
+; CHECK-LABEL: define void @pluto(
+; CHECK-SAME: ) local_unnamed_addr !dbg [[DBG10:![0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[GLOBAL_1_INIT_VAL:%.*]] = load i1, ptr @global.1.init, align 1, !dbg [[DBG11:![0-9]+]]
+; CHECK-NEXT:    [[NOTINIT:%.*]] = xor i1 [[GLOBAL_1_INIT_VAL]], true, !dbg [[DBG12:![0-9]+]]
+; CHECK-NEXT:    unreachable
+;
+entry:
+  %0 = load ptr, ptr @global.1, align 8, !dbg !11
+  %.not = icmp eq ptr %0, null, !dbg !12
+  unreachable
+}
+
+declare ptr @_Znwm(i64)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 20.0.0git", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2, globals: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "preserve-load-dbgloc.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !DILocation(line: 10, column: 1, scope: !5)
+!5 = distinct !DILexicalBlock(scope: !7, file: !6, line: 1524, column: 3)
+!6 = !DIFile(filename: "preserve-load-dbgloc.c", directory: "/tmp")
+!7 = distinct !DISubprogram(name: "ham", scope: !6, file: !6, line: 10, type: !8, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!8 = distinct !DISubroutineType(types: !2)
+!10 = distinct !DISubprogram(name: "pluto", scope: !6, file: !6, line: 20, type: !8, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!11 = !DILocation(line: 20, column: 2, scope: !10)
+!12 = !DILocation(line: 21, column: 3, scope: !10)
+!13 = distinct !DISubprogram(name: "bar", scope: !6, file: !6, line: 230, type: !8, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!14 = !DILocation(line: 11, column: 4, scope: !13)
+;.
+; CHECK: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C11, file: [[META1:![0-9]+]], producer: "{{.*}}clang version {{.*}}", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: [[META2:![0-9]+]], retainedTypes: [[META2]], globals: [[META2]], splitDebugInlining: false, nameTableKind: None)
+; CHECK: [[META1]] = !DIFile(filename: "preserve-load-dbgloc.c", directory: {{.*}})
+; CHECK: [[META2]] = !{}
+; CHECK: [[DBG4]] = distinct !DISubprogram(name: "ham", scope: [[META1]], file: [[META1]], line: 10, type: [[META5:![0-9]+]], flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META2]])
+; CHECK: [[META5]] = distinct !DISubroutineType(types: [[META2]])
+; CHECK: [[DBG6]] = !DILocation(line: 10, column: 1, scope: [[META7:![0-9]+]])
+; CHECK: [[META7]] = distinct !DILexicalBlock(scope: [[DBG4]], file: [[META1]], line: 1524, column: 3)
+; CHECK: [[DBG8]] = distinct !DISubprogram(name: "bar", scope: [[META1]], file: [[META1]], line: 230, type: [[META5]], flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META2]])
+; CHECK: [[DBG9]] = !DILocation(line: 11, column: 4, scope: [[DBG8]])
+; CHECK: [[DBG10]] = distinct !DISubprogram(name: "pluto", scope: [[META1]], file: [[META1]], line: 20, type: [[META5]], flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META2]])
+; CHECK: [[DBG11]] = !DILocation(line: 20, column: 2, scope: [[DBG10]])
+; CHECK: [[DBG12]] = !DILocation(line: 21, column: 3, scope: [[DBG10]])
+;.