[MLIR][DebugInfo] Set debug info format in MLIR->IR translation (#95329)

MLIR's LLVM dialect does not internally support debug records, only
converting to/from debug intrinsics. To smooth the transition from
intrinsics to records, there is a step prior to IR->MLIR translation
that switches the IR module to intrinsic-form; this patch adds the
equivalent conversion to record-form at MLIR->IR translation.

This is a partial reapply of
#95098 which can be landed once
the flang frontend has been updated by
#95306. This is the counterpart
to the earlier patch #89735
which handled the IR->MLIR conversion.

Author: SLTozer

mlir/lib/Target/LLVMIR/ConvertToLLVMIR.cpp

@@ -16,9 +16,12 @@
 #include "mlir/Target/LLVMIR/Dialect/All.h"
 #include "mlir/Target/LLVMIR/Export.h"
 #include "mlir/Tools/mlir-translate/Translation.h"
+#include "llvm/IR/DebugProgramInstruction.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 
+extern llvm::cl::opt<bool> WriteNewDbgInfoFormat;
+
 using namespace mlir;
 
 namespace mlir {
@@ -31,6 +34,13 @@ void registerToLLVMIRTranslation() {
         if (!llvmModule)
           return failure();
 
+        // When printing LLVM IR, we should convert the module to the debug info
+        // format that LLVM expects us to print.
+        // See https://llvm.org/docs/RemoveDIsDebugInfo.html
+        llvm::ScopedDbgInfoFormatSetter formatSetter(*llvmModule,
+                                                     WriteNewDbgInfoFormat);
+        if (WriteNewDbgInfoFormat)
+          llvmModule->removeDebugIntrinsicDeclarations();
         llvmModule->print(output, nullptr);
         return success();
       },

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

@@ -64,6 +64,8 @@ using namespace mlir;
 using namespace mlir::LLVM;
 using namespace mlir::LLVM::detail;
 
+extern llvm::cl::opt<bool> UseNewDbgInfoFormat;
+
 #include "mlir/Dialect/LLVMIR/LLVMConversionEnumsToLLVM.inc"
 
 namespace {
@@ -1801,6 +1803,9 @@ prepareLLVMModule(Operation *m, llvm::LLVMContext &llvmContext,
                   StringRef name) {
   m->getContext()->getOrLoadDialect<LLVM::LLVMDialect>();
   auto llvmModule = std::make_unique<llvm::Module>(name, llvmContext);
+  // ModuleTranslation can currently only construct modules in the old debug
+  // info format, so set the flag accordingly.
+  llvmModule->setNewDbgInfoFormatFlag(false);
   if (auto dataLayoutAttr =
           m->getDiscardableAttr(LLVM::LLVMDialect::getDataLayoutAttrName())) {
     llvmModule->setDataLayout(cast<StringAttr>(dataLayoutAttr).getValue());
@@ -1879,6 +1884,11 @@ mlir::translateModuleToLLVMIR(Operation *module, llvm::LLVMContext &llvmContext,
   if (failed(translator.convertFunctions()))
     return nullptr;
 
+  // Once we've finished constructing elements in the module, we should convert
+  // it to use the debug info format desired by LLVM.
+  // See https://llvm.org/docs/RemoveDIsDebugInfo.html
+  translator.llvmModule->setIsNewDbgInfoFormat(UseNewDbgInfoFormat);
+
   if (!disableVerification &&
       llvm::verifyModule(*translator.llvmModule, &llvm::errs()))
     return nullptr;

mlir/test/Target/LLVMIR/llvmir-debug.mlir

@@ -1,4 +1,5 @@
-// RUN: mlir-translate -mlir-to-llvmir --split-input-file %s | FileCheck %s
+// RUN: mlir-translate -mlir-to-llvmir --write-experimental-debuginfo=false --split-input-file %s | FileCheck %s --check-prefixes=CHECK,INTRINSICS
+// RUN: mlir-translate -mlir-to-llvmir --write-experimental-debuginfo=true --split-input-file %s | FileCheck %s --check-prefixes=CHECK,RECORDS
 
 // CHECK-LABEL: define void @func_with_empty_named_info()
 // Check that translation doens't crash in the presence of an inlineble call
@@ -98,13 +99,16 @@ llvm.func @func_with_debug(%arg: i64) {
   %allocCount = llvm.mlir.constant(1 : i32) : i32
   %alloc = llvm.alloca %allocCount x i64 : (i32) -> !llvm.ptr
 
-  // CHECK: call void @llvm.dbg.value(metadata i64 %[[ARG]], metadata ![[VAR_LOC:[0-9]+]], metadata !DIExpression(DW_OP_LLVM_fragment, 0, 1))
+  // INTRINSICS: call void @llvm.dbg.value(metadata i64 %[[ARG]], metadata ![[VAR_LOC:[0-9]+]], metadata !DIExpression(DW_OP_LLVM_fragment, 0, 1))
+  // RECORDS: #dbg_value(i64 %[[ARG]], ![[VAR_LOC:[0-9]+]], !DIExpression(DW_OP_LLVM_fragment, 0, 1), !{{.*}})
   llvm.intr.dbg.value #variable #llvm.di_expression<[DW_OP_LLVM_fragment(0, 1)]> = %arg : i64
 
-  // CHECK: call void @llvm.dbg.declare(metadata ptr %[[ALLOC]], metadata ![[ADDR_LOC:[0-9]+]], metadata !DIExpression(DW_OP_deref, DW_OP_LLVM_convert, 4, DW_ATE_signed))
+  // INTRINSICS: call void @llvm.dbg.declare(metadata ptr %[[ALLOC]], metadata ![[ADDR_LOC:[0-9]+]], metadata !DIExpression(DW_OP_deref, DW_OP_LLVM_convert, 4, DW_ATE_signed))
+  // RECORDS: #dbg_declare(ptr %[[ALLOC]], ![[ADDR_LOC:[0-9]+]], !DIExpression(DW_OP_deref, DW_OP_LLVM_convert, 4, DW_ATE_signed), !{{.*}})
   llvm.intr.dbg.declare #variableAddr #llvm.di_expression<[DW_OP_deref, DW_OP_LLVM_convert(4, DW_ATE_signed)]> = %alloc : !llvm.ptr
 
-  // CHECK: call void @llvm.dbg.value(metadata i64 %[[ARG]], metadata ![[NO_NAME_VAR:[0-9]+]], metadata !DIExpression())
+  // INTRINSICS: call void @llvm.dbg.value(metadata i64 %[[ARG]], metadata ![[NO_NAME_VAR:[0-9]+]], metadata !DIExpression())
+  // RECORDS: #dbg_value(i64 %[[ARG]], ![[NO_NAME_VAR:[0-9]+]], !DIExpression(), !{{.*}})
   llvm.intr.dbg.value #noNameVariable = %arg : i64
 
   // CHECK: call void @func_no_debug(), !dbg ![[FILE_LOC:[0-9]+]]
@@ -219,11 +223,14 @@ llvm.func @func_decl_with_subprogram() -> (i32) loc(fused<#di_subprogram>["foo.m
 // CHECK-LABEL: define i32 @func_with_inlined_dbg_value(
 // CHECK-SAME: i32 %[[ARG:.*]]) !dbg ![[OUTER_FUNC:[0-9]+]]
 llvm.func @func_with_inlined_dbg_value(%arg0: i32) -> (i32) {
-  // CHECK: call void @llvm.dbg.value(metadata i32 %[[ARG]], metadata ![[VAR_LOC0:[0-9]+]], metadata !DIExpression()), !dbg ![[DBG_LOC0:.*]]
+  // INTRINSICS: call void @llvm.dbg.value(metadata i32 %[[ARG]], metadata ![[VAR_LOC0:[0-9]+]], metadata !DIExpression()), !dbg ![[DBG_LOC0:.*]]
+  // RECORDS: #dbg_value(i32 %[[ARG]], ![[VAR_LOC0:[0-9]+]], !DIExpression(), ![[DBG_LOC0:.*]])
   llvm.intr.dbg.value #di_local_variable0 = %arg0 : i32 loc(fused<#di_subprogram>[#loc0])
-  // CHECK: call void @llvm.dbg.value(metadata i32 %[[ARG]], metadata ![[VAR_LOC1:[0-9]+]], metadata !DIExpression()), !dbg ![[DBG_LOC1:.*]]
+  // INTRINSICS: call void @llvm.dbg.value(metadata i32 %[[ARG]], metadata ![[VAR_LOC1:[0-9]+]], metadata !DIExpression()), !dbg ![[DBG_LOC1:.*]]
+  // RECORDS: #dbg_value(i32 %[[ARG]], ![[VAR_LOC1:[0-9]+]], !DIExpression(), ![[DBG_LOC1:.*]])
   llvm.intr.dbg.value #di_local_variable1 = %arg0 : i32 loc(#loc1)
-  // CHECK: call void @llvm.dbg.label(metadata ![[LABEL:[0-9]+]]), !dbg ![[DBG_LOC1:.*]]
+  // INTRINSICS: call void @llvm.dbg.label(metadata ![[LABEL:[0-9]+]]), !dbg ![[DBG_LOC1:.*]]
+  // RECORDS: #dbg_label(![[LABEL:[0-9]+]], ![[DBG_LOC1:.*]])
   llvm.intr.dbg.label #di_label loc(#loc1)
   llvm.return %arg0 : i32
 } loc(fused<#di_subprogram>["caller"])
@@ -254,7 +261,8 @@ llvm.func @func_with_inlined_dbg_value(%arg0: i32) -> (i32) {
 // CHECK-LABEL: define void @func_without_subprogram(
 // CHECK-SAME: i32 %[[ARG:.*]])
 llvm.func @func_without_subprogram(%0 : i32) {
-  // CHECK: call void @llvm.dbg.value(metadata i32 %[[ARG]], metadata ![[VAR_LOC:[0-9]+]], metadata !DIExpression()), !dbg ![[DBG_LOC0:.*]]
+  // INTRINSICS: call void @llvm.dbg.value(metadata i32 %[[ARG]], metadata ![[VAR_LOC:[0-9]+]], metadata !DIExpression()), !dbg ![[DBG_LOC0:.*]]
+  // RECORDS: #dbg_value(i32 %[[ARG]], ![[VAR_LOC:[0-9]+]], !DIExpression(), ![[DBG_LOC0:.*]])
   llvm.intr.dbg.value #di_local_variable = %0 : i32 loc(fused<#di_subprogram>[#loc])
   llvm.return
 }
@@ -285,11 +293,14 @@ llvm.func @func_without_subprogram(%0 : i32) {
 llvm.func @dbg_intrinsics_with_no_location(%arg0: i32) -> (i32) {
   %allocCount = llvm.mlir.constant(1 : i32) : i32
   %alloc = llvm.alloca %allocCount x i64 : (i32) -> !llvm.ptr
-  // CHECK-NOT: @llvm.dbg.value
+  // INTRINSICS-NOT: @llvm.dbg.value
+  // RECORDS-NOT: #dbg_value
   llvm.intr.dbg.value #di_local_variable = %arg0 : i32
-  // CHECK-NOT: @llvm.dbg.declare
+  // INTRINSICS-NOT: @llvm.dbg.declare
+  // RECORDS-NOT: #dbg_declare
   llvm.intr.dbg.declare #declared_var = %alloc : !llvm.ptr
-  // CHECK-NOT: @llvm.dbg.label
+  // INTRINSICS-NOT: @llvm.dbg.label
+  // RECORDS-NOT: #dbg_label
   llvm.intr.dbg.label #di_label
   llvm.return %arg0 : i32
 }

mlir/test/lib/Dialect/Test/TestToLLVMIRTranslation.cpp

@@ -22,6 +22,9 @@
 #include "mlir/Tools/mlir-translate/Translation.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/TypeSwitch.h"
+#include "llvm/IR/DebugProgramInstruction.h"
+
+extern llvm::cl::opt<bool> WriteNewDbgInfoFormat;
 
 using namespace mlir;
 
@@ -122,6 +125,13 @@ void registerTestToLLVMIR() {
         if (!llvmModule)
           return failure();
 
+        // When printing LLVM IR, we should convert the module to the debug info
+        // format that LLVM expects us to print.
+        // See https://llvm.org/docs/RemoveDIsDebugInfo.html
+        llvm::ScopedDbgInfoFormatSetter formatSetter(*llvmModule,
+                                                     WriteNewDbgInfoFormat);
+        if (WriteNewDbgInfoFormat)
+          llvmModule->removeDebugIntrinsicDeclarations();
         llvmModule->print(output, nullptr);
         return success();
       },