[llvm] [mlir] [OMPIRBuilder] Move debug records to correct blocks. (PR #158113)
Abid Qadeer via llvm-commits
llvm-commits at lists.llvm.org
Thu Sep 11 09:52:28 PDT 2025
https://github.com/abidh created https://github.com/llvm/llvm-project/pull/158113
Consider the following small OpenMP target region:
```
!$omp target map(tofrom: x)
x = x + 1
!$omp end target
```
Currently, when compiled with flang, it will generate an outlined function like below (with irrelevant bits removed).
```
void @__omp_offloading_10303_14e8afc__QQmain_l13(ptr %0, ptr %1) { entry:
%2 = alloca ptr, align 8, addrspace(5)
%3 = addrspacecast ptr addrspace(5) %2 to ptr
...
br i1 %exec_user_code, label %user_code.entry, label %worker.exit
user_code.entry:
%5 = load ptr, ptr %3, align 8, !align !19
br label %omp.region.after_alloca
omp.region.after_alloca:
br label %outlined.body
outlined.body:
br label %omp.target
omp.target:
#dbg_declare(ptr addrspace(5) %2, !20, !DIExpression(), !21)
...
br label %omp.region.cont, !dbg !23
omp.region.cont:
call void @__kmpc_target_deinit()
ret void
worker.exit:
ret void
}
```
Due to how various basic blocks are generated to implement target region for device, the debug record for variable x end up in a different block to the location of the variable (%5 in this case). The backend can drop such debug records.
This PR moves such records in the correct block. If the location field of the debug record is an Instruction, it will ensure that debug record is in same block as the instruction. If the location is an Argument, the debug record will be moved to the entry block.
Some minor cleanup in the `UpdateDebugRecord` as that brings it to use the similar logic as in `MoveDebugRecordToCorrectBlock`.
>From 67ac1847a1dbd5371ac82dfca14a32499fd3bf94 Mon Sep 17 00:00:00 2001
From: Abid Qadeer <haqadeer at amd.com>
Date: Wed, 3 Sep 2025 22:26:06 +0100
Subject: [PATCH] [OMPIRBuilder] Move debug records to correct blocks.
Consider the following small OpenMP target region:
!$omp target map(tofrom: x)
x = x + 1
!$omp end target
Currently, when compiled with flang, it will generate an outlined
function like below (with irrelevent bits removed).
void @__omp_offloading_10303_14e8afc__QQmain_l13(ptr %0, ptr %1) {
entry:
%2 = alloca ptr, align 8, addrspace(5)
%3 = addrspacecast ptr addrspace(5) %2 to ptr
...
br i1 %exec_user_code, label %user_code.entry, label %worker.exit
user_code.entry:
%5 = load ptr, ptr %3, align 8, !align !19
br label %omp.region.after_alloca
omp.region.after_alloca:
br label %outlined.body
outlined.body:
br label %omp.target
omp.target:
#dbg_declare(ptr addrspace(5) %2, !20, !DIExpression(), !21)
...
br label %omp.region.cont, !dbg !23
omp.region.cont:
call void @__kmpc_target_deinit()
ret void
worker.exit: ; preds = %entry
ret void
}
Due to how various basic blocks are generated, the debug record for
variable x end up in a different block to the location of the variable
(%5 in this case). The backend drops such debug records.
This PR moves such records in the correct block. If the location field
of the debug record is an instruction, it will ensure that debug record
is in same block as the instruction. If the location is an argument, the
debug record will be moved to the entry block.
---
llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp | 43 ++++--
.../Frontend/OpenMPIRBuilderTest.cpp | 122 ++++++++++++++++++
.../LLVMIR/omptarget-debug-record-pos.mlir | 47 +++++++
.../Target/LLVMIR/omptarget-debug-var-1.mlir | 8 +-
4 files changed, 207 insertions(+), 13 deletions(-)
create mode 100644 mlir/test/Target/LLVMIR/omptarget-debug-record-pos.mlir
diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
index 03ea58318d4a9..4a9fa382f9638 100644
--- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
+++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
@@ -7364,29 +7364,54 @@ static void FixupDebugInfoForOutlinedFunction(
OldVar->getFlags(), OldVar->getAlignInBits(), OldVar->getAnnotations());
return NewVar;
};
-
- auto UpdateDebugRecord = [&](auto *DR) {
+ auto UpdateDebugRecord = [&](DbgVariableRecord *DR) {
DILocalVariable *OldVar = DR->getVariable();
unsigned ArgNo = 0;
- for (auto Loc : DR->location_ops()) {
- auto Iter = ValueReplacementMap.find(Loc);
- if (Iter != ValueReplacementMap.end()) {
- DR->replaceVariableLocationOp(Loc, std::get<0>(Iter->second));
- ArgNo = std::get<1>(Iter->second) + 1;
- }
+ if (DR->getNumVariableLocationOps() != 1u)
+ return;
+ auto Loc = DR->getVariableLocationOp(0u);
+ auto Iter = ValueReplacementMap.find(Loc);
+ if (Iter != ValueReplacementMap.end()) {
+ DR->replaceVariableLocationOp(Loc, std::get<0>(Iter->second));
+ ArgNo = std::get<1>(Iter->second) + 1;
}
if (ArgNo != 0)
DR->setVariable(GetUpdatedDIVariable(OldVar, ArgNo));
};
+ SmallVector<DbgVariableRecord *, 4> DVRsToDelete;
+ auto MoveDebugRecordToCorrectBlock = [&](DbgVariableRecord *DVR) {
+ if (DVR->getNumVariableLocationOps() != 1u)
+ return;
+ auto Loc = DVR->getVariableLocationOp(0u);
+ BasicBlock *CurBB = DVR->getParent();
+ BasicBlock *RequiredBB = nullptr;
+
+ if (Instruction *LocInst = dyn_cast<Instruction>(Loc))
+ RequiredBB = LocInst->getParent();
+ else if (isa<llvm::Argument>(Loc))
+ RequiredBB = &(DVR->getFunction()->getEntryBlock());
+
+ if (RequiredBB && RequiredBB != CurBB) {
+ assert(!RequiredBB->empty());
+ RequiredBB->insertDbgRecordBefore(DVR->clone(),
+ RequiredBB->back().getIterator());
+ DVRsToDelete.push_back(DVR);
+ }
+ };
+
// The location and scope of variable intrinsics and records still point to
// the parent function of the target region. Update them.
for (Instruction &I : instructions(Func)) {
assert(!isa<llvm::DbgVariableIntrinsic>(&I) &&
"Unexpected debug intrinsic");
- for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange()))
+ for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange())) {
UpdateDebugRecord(&DVR);
+ MoveDebugRecordToCorrectBlock(&DVR);
+ }
}
+ for (auto *DVR : DVRsToDelete)
+ DVR->getMarker()->MarkedInstr->dropOneDbgRecord(DVR);
// An extra argument is passed to the device. Create the debug data for it.
if (OMPBuilder.Config.isTargetDevice()) {
DICompileUnit *CU = NewSP->getUnit();
diff --git a/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp b/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp
index c13570dc803b3..01a4383b089f2 100644
--- a/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp
+++ b/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp
@@ -7078,6 +7078,128 @@ TEST_F(OpenMPIRBuilderTest, ConstantAllocaRaise) {
EXPECT_TRUE(isa<ReturnInst>(ExitBlock->getFirstNonPHIIt()));
}
+TEST_F(OpenMPIRBuilderTest, DebugRecordLoc) {
+ OpenMPIRBuilder OMPBuilder(*M);
+ OMPBuilder.setConfig(
+ OpenMPIRBuilderConfig(true, false, false, false, false, false, false));
+ OMPBuilder.initialize();
+
+ Function *OutlinedFn = nullptr;
+ F->setName("func");
+ IRBuilder<> Builder(BB);
+ OpenMPIRBuilder::LocationDescription Loc({Builder.saveIP(), DL});
+ Builder.SetCurrentDebugLocation(DL);
+ auto *Alloca = Builder.CreateAlloca(Builder.getInt32Ty());
+
+ llvm::SmallVector<llvm::Value *, 1> CapturedArgs = {
+ Alloca, Constant::getNullValue(PointerType::get(Ctx, 0))};
+
+ auto SimpleArgAccessorCB =
+ [&](llvm::Argument &Arg, llvm::Value *Input, llvm::Value *&RetVal,
+ llvm::OpenMPIRBuilder::InsertPointTy AllocaIP,
+ llvm::OpenMPIRBuilder::InsertPointTy CodeGenIP) {
+ IRBuilderBase::InsertPointGuard guard(Builder);
+ Builder.SetCurrentDebugLocation(llvm::DebugLoc());
+ if (!OMPBuilder.Config.isTargetDevice()) {
+ RetVal = cast<llvm::Value>(&Arg);
+ return CodeGenIP;
+ }
+ Builder.restoreIP(AllocaIP);
+ llvm::Value *Addr = Builder.CreateAlloca(
+ Arg.getType()->isPointerTy()
+ ? Arg.getType()
+ : Type::getInt64Ty(Builder.getContext()),
+ OMPBuilder.M.getDataLayout().getAllocaAddrSpace());
+ llvm::Value *AddrAscast =
+ Builder.CreatePointerBitCastOrAddrSpaceCast(Addr, Input->getType());
+ Builder.CreateStore(&Arg, AddrAscast);
+ Builder.restoreIP(CodeGenIP);
+ RetVal = Builder.CreateLoad(Arg.getType(), AddrAscast);
+ return Builder.saveIP();
+ };
+
+ llvm::OpenMPIRBuilder::MapInfosTy CombinedInfos;
+ auto GenMapInfoCB = [&](llvm::OpenMPIRBuilder::InsertPointTy codeGenIP)
+ -> llvm::OpenMPIRBuilder::MapInfosTy & {
+ CreateDefaultMapInfos(OMPBuilder, CapturedArgs, CombinedInfos);
+ return CombinedInfos;
+ };
+
+ auto CustomMapperCB = [&](unsigned int I) { return nullptr; };
+ auto BodyGenCB = [&](OpenMPIRBuilder::InsertPointTy AllocaIP,
+ OpenMPIRBuilder::InsertPointTy CodeGenIP)
+ -> OpenMPIRBuilder::InsertPointTy {
+ IRBuilderBase::InsertPointGuard guard(Builder);
+ Builder.SetCurrentDebugLocation(llvm::DebugLoc());
+ Builder.restoreIP(CodeGenIP);
+ auto *mainSP = F->getSubprogram();
+ DIBuilder DIB(*M, false, mainSP->getUnit());
+ auto Type = DIB.createSubroutineType(DIB.getOrCreateTypeArray({}));
+ auto SP = DIB.createFunction(
+ mainSP->getScope(), "target", "", mainSP->getFile(), 2, Type, 2,
+ DINode::FlagZero,
+ DISubprogram::SPFlagDefinition | DISubprogram::SPFlagOptimized);
+ OutlinedFn = CodeGenIP.getBlock()->getParent();
+ OutlinedFn->setSubprogram(SP);
+ DebugLoc Loc = DILocation::get(Ctx, 3, 7, SP);
+ DIType *VoidPtrTy =
+ DIB.createQualifiedType(dwarf::DW_TAG_pointer_type, nullptr);
+ // The location of this variable is in the CapturedArgs so it will get the
+ // alloca/load/store chain in the auto SimpleArgAccessorCB and the location
+ // will change to the load instruction.
+ DILocalVariable *Var1 = DIB.createParameterVariable(
+ SP, "test1", /*ArgNo*/ 1, SP->getFile(), /*LineNo=*/1, VoidPtrTy);
+ DIB.insertDeclare(Alloca, Var1, DIB.createExpression(), Loc,
+ Builder.GetInsertPoint());
+ // This variable will point directly to the function argument.
+ DILocalVariable *Var2 = DIB.createParameterVariable(
+ SP, "test2", /*ArgNo*/ 3, SP->getFile(), /*LineNo=*/1, VoidPtrTy);
+ DIB.insertDeclare(OutlinedFn->getArg(2), Var2, DIB.createExpression(), Loc,
+ Builder.GetInsertPoint());
+
+ return Builder.saveIP();
+ };
+
+ IRBuilder<>::InsertPoint EntryIP(&F->getEntryBlock(),
+ F->getEntryBlock().end());
+ TargetRegionEntryInfo EntryInfo("parent", /*DeviceID=*/1, /*FileID=*/2,
+ /*Line=*/3, /*Count=*/0);
+ OpenMPIRBuilder::TargetKernelRuntimeAttrs RuntimeAttrs;
+ OpenMPIRBuilder::TargetKernelDefaultAttrs DefaultAttrs = {
+ /*ExecFlags=*/omp::OMPTgtExecModeFlags::OMP_TGT_EXEC_MODE_GENERIC,
+ /*MaxTeams=*/{-1}, /*MinTeams=*/0, /*MaxThreads=*/{0}, /*MinThreads=*/0};
+ llvm::OpenMPIRBuilder::TargetDataInfo Info(
+ /*RequiresDevicePointerInfo=*/false,
+ /*SeparateBeginEndCalls=*/true);
+
+ ASSERT_EXPECTED_INIT(
+ OpenMPIRBuilder::InsertPointTy, AfterIP,
+ OMPBuilder.createTarget(Loc, /*IsOffloadEntry=*/true, EntryIP, EntryIP,
+ Info, EntryInfo, DefaultAttrs, RuntimeAttrs,
+ /*IfCond=*/nullptr, CapturedArgs, GenMapInfoCB,
+ BodyGenCB, SimpleArgAccessorCB, CustomMapperCB,
+ {}, false));
+ EXPECT_EQ(DL, Builder.getCurrentDebugLocation());
+ Builder.restoreIP(AfterIP);
+
+ Builder.CreateRetVoid();
+ OMPBuilder.finalize();
+
+ // Check outlined function
+ EXPECT_FALSE(verifyModule(*M, &errs()));
+ EXPECT_NE(OutlinedFn, nullptr);
+ for (Instruction &I : instructions(OutlinedFn)) {
+ for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange())) {
+ EXPECT_EQ(DVR.getNumVariableLocationOps(), 1u);
+ auto Loc = DVR.getVariableLocationOp(0u);
+ if (Instruction *LocInst = dyn_cast<Instruction>(Loc))
+ EXPECT_EQ(DVR.getParent(), LocInst->getParent());
+ else if (isa<llvm::Argument>(Loc))
+ EXPECT_EQ(DVR.getParent(), &(OutlinedFn->getEntryBlock()));
+ }
+ }
+}
+
TEST_F(OpenMPIRBuilderTest, CreateTask) {
using InsertPointTy = OpenMPIRBuilder::InsertPointTy;
OpenMPIRBuilder OMPBuilder(*M);
diff --git a/mlir/test/Target/LLVMIR/omptarget-debug-record-pos.mlir b/mlir/test/Target/LLVMIR/omptarget-debug-record-pos.mlir
new file mode 100644
index 0000000000000..bd89a5c1cdfeb
--- /dev/null
+++ b/mlir/test/Target/LLVMIR/omptarget-debug-record-pos.mlir
@@ -0,0 +1,47 @@
+// RUN: mlir-translate -mlir-to-llvmir %s
+
+#di_basic_type = #llvm.di_basic_type<tag = DW_TAG_base_type, name = "real",
+ sizeInBits = 32, encoding = DW_ATE_float>
+#file = #llvm.di_file<"test.f90" in "">
+#di_null_type = #llvm.di_null_type
+#cu = #llvm.di_compile_unit<id = distinct[0]<>,
+ sourceLanguage = DW_LANG_Fortran95, file = #file, isOptimized = false,
+ emissionKind = Full>
+#sp_ty = #llvm.di_subroutine_type<callingConvention = DW_CC_program,
+ types = #di_null_type>
+#sp = #llvm.di_subprogram<compileUnit = #cu, name = "main", file=#file,
+ subprogramFlags = "Definition", type = #sp_ty>
+#sp1 = #llvm.di_subprogram<compileUnit = #cu, name = "target", file=#file,
+ subprogramFlags = "Definition", type = #sp_ty>
+#var1 = #llvm.di_local_variable<scope = #sp, name = "x", file = #file, line = 2,
+ type = #di_basic_type>
+#var2 = #llvm.di_local_variable<scope = #sp1, name = "x", file = #file,
+ line = 2, type = #di_basic_type>
+
+module attributes {dlti.dl_spec = #dlti.dl_spec<#dlti.dl_entry<"dlti.alloca_memory_space", 5 : ui32>>, llvm.target_triple = "amdgcn-amd-amdhsa", omp.is_target_device = true} {
+ llvm.func @main() {
+ %0 = llvm.mlir.constant(1 : i64) : i64 loc(#loc2)
+ %1 = llvm.alloca %0 x i1 : (i64) -> !llvm.ptr<5> loc(#loc2)
+ %2 = llvm.addrspacecast %1 : !llvm.ptr<5> to !llvm.ptr loc(#loc2)
+ llvm.intr.dbg.declare #var1 = %2 : !llvm.ptr loc(#loc2)
+ %4 = omp.map.info var_ptr(%2 : !llvm.ptr, f32) map_clauses(tofrom) capture(ByRef) -> !llvm.ptr {name = "x"} loc(#loc2)
+ omp.target map_entries(%4 -> %arg0 : !llvm.ptr) {
+ %5 = llvm.mlir.constant(1.000000e+00 : f32) : f32 loc(#loc3)
+ llvm.intr.dbg.declare #var2 = %arg0 : !llvm.ptr loc(#loc3)
+ %6 = llvm.load %arg0 : !llvm.ptr -> f32 loc(#loc3)
+ %7 = llvm.fadd %6, %5 {fastmathFlags = #llvm.fastmath<contract>} : f32 loc(#loc3)
+ llvm.store %7, %arg0 : f32, !llvm.ptr loc(#loc3)
+ omp.terminator loc(#loc3)
+ } loc(#loc4)
+ llvm.return loc(#loc2)
+ } loc(#loc5)
+}
+
+#loc2 = loc("test.f90":6:7)
+#loc3 = loc("test.f90":8:7)
+#loc4 = loc(fused<#sp1>[#loc3])
+#loc5 = loc(fused<#sp>[#loc2])
+
+// CHECK-LABEL: user_code.entry
+// CHECK: %[[LOAD:.*]] = load ptr
+// CHECK-NEXT: #dbg_declare(ptr %[[LOAD]]{{.*}})
diff --git a/mlir/test/Target/LLVMIR/omptarget-debug-var-1.mlir b/mlir/test/Target/LLVMIR/omptarget-debug-var-1.mlir
index 8f42995af23a8..24d8d01a396b9 100644
--- a/mlir/test/Target/LLVMIR/omptarget-debug-var-1.mlir
+++ b/mlir/test/Target/LLVMIR/omptarget-debug-var-1.mlir
@@ -62,7 +62,7 @@ module attributes {dlti.dl_spec = #dlti.dl_spec<#dlti.dl_entry<"dlti.alloca_memo
#loc5 = loc(fused<#sp1>[#loc2])
// CHECK: ![[SP:[0-9]+]] = distinct !DISubprogram(name: "target"{{.*}})
-// CHECK: !DILocalVariable(name: "dyn_ptr", arg: 1, scope: ![[SP]]{{.*}}flags: DIFlagArtificial)
-// CHECK: !DILocalVariable(name: "x", arg: 2, scope: ![[SP]]{{.*}})
-// CHECK: !DILocalVariable(name: "arr", arg: 3, scope: ![[SP]]{{.*}})
-// CHECK: !DILocalVariable(name: "i", arg: 4, scope: ![[SP]]{{.*}})
+// CHECK-DAG: !DILocalVariable(name: "dyn_ptr", arg: 1, scope: ![[SP]]{{.*}}flags: DIFlagArtificial)
+// CHECK-DAG: !DILocalVariable(name: "x", arg: 2, scope: ![[SP]]{{.*}})
+// CHECK-DAG: !DILocalVariable(name: "arr", arg: 3, scope: ![[SP]]{{.*}})
+// CHECK-DAG: !DILocalVariable(name: "i", arg: 4, scope: ![[SP]]{{.*}})
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