[flang][debug] Support fixed size character type. #95462

abidh · 2024-06-13T19:44:46Z

This PR adds debug support for fixed size character type. The character type gets translated to DIStringType.

As I have noticed in comments, currently DIStringType does not have a way to represent the underlying character type of the string. This restricts our ability to represent wide string. As an example, this is how the debugger shows 2 different type of string. Note that non-ascii characters work ok with default kind string.

character(kind=4, len=5) :: str1
character(len=16) :: str2
str1 = 'hello'
str2 = 'π = 3.14'

(gdb) p str1
$1 = 'h\000\000\000e\000\000\000l\000\000\000l\000\000\000o\000\000\000'

(gdb) p str2
$2 = 'π = 3.14 '

This PR adds debug support for fixed size character type. The character type gets translated to DIStringType. As I have noticed in comments, currently DIStringType does not have a way to represent the underlying character type of the string. This restricts our ability to represent wide string. As an example, this is how the debugger shows 2 different type of string. Note that non-ascii characters work ok with default kind string. character(kind=4, len=5) :: str1 character(len=16) :: str2 str1 = 'hello' str2 = 'π = 3.14' (gdb) p str1 $1 = 'h\000\000\000e\000\000\000l\000\000\000l\000\000\000o\000\000\000' (gdb) p str2 $2 = 'π = 3.14 '

llvmbot · 2024-06-13T19:45:19Z

@llvm/pr-subscribers-flang-fir-hlfir

Author: Abid Qadeer (abidh)

Changes

This PR adds debug support for fixed size character type. The character type gets translated to DIStringType.

As I have noticed in comments, currently DIStringType does not have a way to represent the underlying character type of the string. This restricts our ability to represent wide string. As an example, this is how the debugger shows 2 different type of string. Note that non-ascii characters work ok with default kind string.

character(kind=4, len=5) :: str1
character(len=16) :: str2
str1 = 'hello'
str2 = 'π = 3.14'

(gdb) p str1
$1 = 'h\000\000\000e\000\000\000l\000\000\000l\000\000\000o\000\000\000'

(gdb) p str2
$2 = 'π = 3.14 '

Full diff: https://github.com/llvm/llvm-project/pull/95462.diff

4 Files Affected:

(modified) flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp (+29)
(modified) flang/lib/Optimizer/Transforms/DebugTypeGenerator.h (+4)
(added) flang/test/Integration/debug-char-type-1.f90 (+21)
(added) flang/test/Transforms/debug-char-type-1.fir (+19)

diff --git a/flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp b/flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp
index 53745d10fe9e4..abc79010f11cc 100644
--- a/flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp
+++ b/flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp
@@ -190,6 +190,33 @@ mlir::LLVM::DITypeAttr DebugTypeGenerator::convertSequenceType(
       /* associated */ nullptr);
 }
 
+mlir::LLVM::DITypeAttr DebugTypeGenerator::convertCharacterType(
+    fir::CharacterType charTy, mlir::LLVM::DIFileAttr fileAttr,
+    mlir::LLVM::DIScopeAttr scope, mlir::Location loc) {
+  mlir::MLIRContext *context = module.getContext();
+  if (!charTy.hasConstantLen())
+    return genPlaceholderType(context);
+
+  // DWARF 5 says the following about the character encoding in 5.1.1.2.
+  // "DW_ATE_ASCII and DW_ATE_UCS specify encodings for the Fortran 2003
+  // string kinds ASCII (ISO/IEC 646:1991) and ISO_10646 (UCS-4 in ISO/IEC
+  // 10646:2000)."
+  unsigned encoding = llvm::dwarf::DW_ATE_ASCII;
+  if (charTy.getFKind() != 1)
+    encoding = llvm::dwarf::DW_ATE_UCS;
+
+  // FIXME: Currently the DIStringType in llvm does not have the option to set
+  // type of the underlying character. This restricts out ability to represent
+  // string with non-default characters. Please see issue #95440 for more
+  // details.
+  return mlir::LLVM::DIStringTypeAttr::get(
+      context, llvm::dwarf::DW_TAG_string_type,
+      mlir::StringAttr::get(context, ""),
+      charTy.getLen() * kindMapping.getCharacterBitsize(charTy.getFKind()),
+      /* alignInBits */ 0, /* stringLength */ nullptr,
+      /* stringLengthExp */ nullptr, /* stringLocationExp */ nullptr, encoding);
+}
+
 mlir::LLVM::DITypeAttr
 DebugTypeGenerator::convertType(mlir::Type Ty, mlir::LLVM::DIFileAttr fileAttr,
                                 mlir::LLVM::DIScopeAttr scope,
@@ -224,6 +251,8 @@ DebugTypeGenerator::convertType(mlir::Type Ty, mlir::LLVM::DIFileAttr fileAttr,
                         bitWidth * 2, llvm::dwarf::DW_ATE_complex_float);
   } else if (auto seqTy = mlir::dyn_cast_or_null<fir::SequenceType>(Ty)) {
     return convertSequenceType(seqTy, fileAttr, scope, loc);
+  } else if (auto charTy = mlir::dyn_cast_or_null<fir::CharacterType>(Ty)) {
+    return convertCharacterType(charTy, fileAttr, scope, loc);
   } else if (auto boxTy = mlir::dyn_cast_or_null<fir::BoxType>(Ty)) {
     auto elTy = boxTy.getElementType();
     if (auto seqTy = mlir::dyn_cast_or_null<fir::SequenceType>(elTy))
diff --git a/flang/lib/Optimizer/Transforms/DebugTypeGenerator.h b/flang/lib/Optimizer/Transforms/DebugTypeGenerator.h
index 11515d11dfed6..aa26694ab5114 100644
--- a/flang/lib/Optimizer/Transforms/DebugTypeGenerator.h
+++ b/flang/lib/Optimizer/Transforms/DebugTypeGenerator.h
@@ -45,6 +45,10 @@ class DebugTypeGenerator {
                            mlir::LLVM::DIFileAttr fileAttr,
                            mlir::LLVM::DIScopeAttr scope, mlir::Location loc,
                            bool genAllocated, bool genAssociated);
+  mlir::LLVM::DITypeAttr convertCharacterType(fir::CharacterType charTy,
+                                              mlir::LLVM::DIFileAttr fileAttr,
+                                              mlir::LLVM::DIScopeAttr scope,
+                                              mlir::Location loc);
   mlir::ModuleOp module;
   KindMapping kindMapping;
   std::uint64_t dimsSize;
diff --git a/flang/test/Integration/debug-char-type-1.f90 b/flang/test/Integration/debug-char-type-1.f90
new file mode 100644
index 0000000000000..a0aebd3125c6e
--- /dev/null
+++ b/flang/test/Integration/debug-char-type-1.f90
@@ -0,0 +1,21 @@
+! RUN: %flang_fc1 -emit-llvm -debug-info-kind=standalone %s -o - | FileCheck  %s
+
+module helper
+  character(len=40) :: str
+end module helper
+
+program test
+  use helper
+  character(kind=4, len=8) :: first
+  character(len=10) :: second
+  first = '3.14 = π'
+  second = 'Fortran'
+  str = 'Hello World!'
+end program test
+
+! CHECK-DAG: !DIGlobalVariable(name: "str"{{.*}}type: ![[TY40:[0-9]+]]{{.*}})
+! CHECK-DAG: ![[TY40]] = !DIStringType(size: 320, encoding: DW_ATE_ASCII)
+! CHECK-DAG: !DILocalVariable(name: "first"{{.*}}type: ![[TY8:[0-9]+]])
+! CHECK-DAG: ![[TY8]] = !DIStringType(size: 256, encoding: DW_ATE_UCS)
+! CHECK-DAG: !DILocalVariable(name: "second"{{.*}}type: ![[TY10:[0-9]+]])
+! CHECK-DAG: ![[TY10]] = !DIStringType(size: 80, encoding: DW_ATE_ASCII)
\ No newline at end of file
diff --git a/flang/test/Transforms/debug-char-type-1.fir b/flang/test/Transforms/debug-char-type-1.fir
new file mode 100644
index 0000000000000..cdce3b7b8b334
--- /dev/null
+++ b/flang/test/Transforms/debug-char-type-1.fir
@@ -0,0 +1,19 @@
+// RUN: fir-opt --add-debug-info --mlir-print-debuginfo %s | FileCheck %s
+
+module attributes {dlti.dl_spec = #dlti.dl_spec<>} {
+  fir.global @_QMhelperEstr1 : !fir.char<1,40> {
+    %0 = fir.zero_bits !fir.char<1,40>
+    fir.has_value %0 : !fir.char<1,40>
+  } loc(#loc1)
+  fir.global @_QMhelperEstr2 : !fir.char<4,20> {
+    %0 = fir.zero_bits !fir.char<4,20>
+    fir.has_value %0 : !fir.char<4,20>
+  } loc(#loc1)
+}
+#loc1 = loc("string.f90":1:1)
+
+// CHECK-DAG: #[[TY1:.*]] = #llvm.di_string_type<tag = DW_TAG_string_type, name = "", sizeInBits = 320, encoding = DW_ATE_ASCII>
+// CHECK-DAG: #llvm.di_global_variable<{{.*}}name = "str1"{{.*}}type = #[[TY1]]{{.*}}>
+// CHECK-DAG: #[[TY2:.*]] = #llvm.di_string_type<tag = DW_TAG_string_type, name = "", sizeInBits = 640, encoding = DW_ATE_UCS>
+// CHECK-DAG: #llvm.di_global_variable<{{.*}}name = "str2"{{.*}}type = #[[TY2]]{{.*}}>
+

flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp

tblah

LGTM, thanks!

vzakhari

LGTM. Thank you!

vzakhari · 2024-06-14T17:06:23Z

flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp

+      context, llvm::dwarf::DW_TAG_string_type,
+      mlir::StringAttr::get(context, ""),
+      charTy.getLen() * kindMapping.getCharacterBitsize(charTy.getFKind()),
+      /* alignInBits */ 0, /* stringLength */ nullptr,


nit: the usual style for these comments is /*alignBits=*/ (no spaces and = at the end).

I will fix it here and throughout the file in a separete PR. Thanks.

jeanPerier

LGTM

As mentioned in [here](#95462 (comment)), the formatting of the comments have been fixed. Also added comments before literal arguments.

abidh requested review from tblah, kiranchandramohan, jeanPerier, klausler, jinisusan, kiranktp and vzakhari June 13, 2024 19:44

llvmbot added flang Flang issues not falling into any other category flang:fir-hlfir labels Jun 13, 2024

klausler removed their request for review June 13, 2024 21:39

abidh requested a review from dpalermo June 14, 2024 09:54

tblah reviewed Jun 14, 2024

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flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp Show resolved Hide resolved

tblah approved these changes Jun 14, 2024

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vzakhari approved these changes Jun 14, 2024

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jeanPerier approved these changes Jun 17, 2024

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Fix comments formatting.

64eb519

abidh merged commit 7e4f7fc into llvm:main Jun 17, 2024
7 checks passed

abidh mentioned this pull request Jun 17, 2024

[flang] Fix comments and formatting. (NFC) #95786

Merged

jpienaar mentioned this pull request Jun 17, 2024

[mlirc] Add missing extern C #95829

Merged

abidh added a commit that referenced this pull request Jun 17, 2024

[flang] Fix comments and formatting. (NFC) (#95786)

7ddff3a

As mentioned in [here](#95462 (comment)), the formatting of the comments have been fixed. Also added comments before literal arguments.

shiltian mentioned this pull request Jun 18, 2024

[MLIR] Fix an assert that contains a mistake in conditional operator (#95668) shiltian/llvm-project#6

Closed

abidh deleted the char_type branch February 5, 2025 18:38

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