[clang] [LLVM] Add new attribute `optdebug` to optimize for debugging (PR #66632)
Stephen Tozer via cfe-commits
cfe-commits at lists.llvm.org
Wed Oct 18 08:31:37 PDT 2023
https://github.com/SLTozer updated https://github.com/llvm/llvm-project/pull/66632
>From eccff5693ebcaac45a7ddf56cbb33a48de281041 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <Stephen.Tozer at Sony.com>
Date: Mon, 18 Sep 2023 09:59:11 +0100
Subject: [PATCH 1/3] [LLVM] Add new attribute `optdebug` to optimize for
debugging
This patch adds a new fn attribute, `optdebug`, that specifies that
optimizations should make decisions that prioritize debug info quality,
potentially at the cost of runtime performance.
This patch does not add any functional changes triggered by this attribute,
only the attribute itself.
---
clang/lib/CodeGen/CodeGenModule.cpp | 1 +
llvm/docs/BitCodeFormat.rst | 1 +
llvm/docs/LangRef.rst | 4 ++++
llvm/include/llvm/Bitcode/LLVMBitCodes.h | 1 +
llvm/include/llvm/IR/Attributes.td | 3 +++
llvm/lib/Bitcode/Reader/BitcodeReader.cpp | 2 ++
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | 2 ++
llvm/lib/Transforms/Utils/CodeExtractor.cpp | 1 +
llvm/test/Bitcode/attributes.ll | 7 +++++++
llvm/utils/emacs/llvm-mode.el | 2 +-
llvm/utils/kate/llvm.xml | 1 +
llvm/utils/vim/syntax/llvm.vim | 1 +
12 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index b1a6683a66bd052..875952232e24b86 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2347,6 +2347,7 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
B.addAttribute(llvm::Attribute::Naked);
// OptimizeNone wins over OptimizeForSize and MinSize.
+ F->removeFnAttr(llvm::Attribute::OptimizeForDebugging);
F->removeFnAttr(llvm::Attribute::OptimizeForSize);
F->removeFnAttr(llvm::Attribute::MinSize);
} else if (D->hasAttr<NakedAttr>()) {
diff --git a/llvm/docs/BitCodeFormat.rst b/llvm/docs/BitCodeFormat.rst
index db913f59d691d71..5742f8594e99908 100644
--- a/llvm/docs/BitCodeFormat.rst
+++ b/llvm/docs/BitCodeFormat.rst
@@ -1093,6 +1093,7 @@ The integer codes are mapped to well-known attributes as follows.
* code 85: ``skipprofile``
* code 86: ``memory``
* code 87: ``nofpclass``
+* code 88: ``optdebug``
.. note::
The ``allocsize`` attribute has a special encoding for its arguments. Its two
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 798b0ab6c593ab4..b74c61d8a9aed9c 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -2025,6 +2025,10 @@ example:
Note: Comparing address of a global variable to ``null`` may still
evaluate to false because of a limitation in querying this attribute inside
constant expressions.
+``optdebug``
+ This attribute suggests that optimization passes and code generator passes
+ should make choices that try to preserve debug info without significantly
+ degrading runtime performance.
``optforfuzzing``
This attribute indicates that this function should be optimized
for maximum fuzzing signal.
diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
index 52e76356a892e45..5d7be5ca936ad37 100644
--- a/llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -713,6 +713,7 @@ enum AttributeKindCodes {
ATTR_KIND_SKIP_PROFILE = 85,
ATTR_KIND_MEMORY = 86,
ATTR_KIND_NOFPCLASS = 87,
+ ATTR_KIND_OPTIMIZE_FOR_DEBUGGING = 88,
};
enum ComdatSelectionKindCodes {
diff --git a/llvm/include/llvm/IR/Attributes.td b/llvm/include/llvm/IR/Attributes.td
index aba1d718f7f72f9..fda79f5f24495fb 100644
--- a/llvm/include/llvm/IR/Attributes.td
+++ b/llvm/include/llvm/IR/Attributes.td
@@ -200,6 +200,9 @@ def NoSanitizeCoverage : EnumAttr<"nosanitize_coverage", [FnAttr]>;
/// Null pointer in address space zero is valid.
def NullPointerIsValid : EnumAttr<"null_pointer_is_valid", [FnAttr]>;
+/// Select optimizations that give decent debug info.
+def OptimizeForDebugging : EnumAttr<"optdebug", [FnAttr]>;
+
/// Select optimizations for best fuzzing signal.
def OptForFuzzing : EnumAttr<"optforfuzzing", [FnAttr]>;
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 1d1ec988a93d847..16eafa6e18f5d59 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1980,6 +1980,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
return Attribute::NoSanitizeCoverage;
case bitc::ATTR_KIND_NULL_POINTER_IS_VALID:
return Attribute::NullPointerIsValid;
+ case bitc::ATTR_KIND_OPTIMIZE_FOR_DEBUGGING:
+ return Attribute::OptimizeForDebugging;
case bitc::ATTR_KIND_OPT_FOR_FUZZING:
return Attribute::OptForFuzzing;
case bitc::ATTR_KIND_OPTIMIZE_FOR_SIZE:
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index e991d055f33474b..c427459508ecfc8 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -747,6 +747,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
return bitc::ATTR_KIND_NO_SANITIZE_COVERAGE;
case Attribute::NullPointerIsValid:
return bitc::ATTR_KIND_NULL_POINTER_IS_VALID;
+ case Attribute::OptimizeForDebugging:
+ return bitc::ATTR_KIND_OPTIMIZE_FOR_DEBUGGING;
case Attribute::OptForFuzzing:
return bitc::ATTR_KIND_OPT_FOR_FUZZING;
case Attribute::OptimizeForSize:
diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
index 08b2b01b2ee1e23..ae7ed296c45ea88 100644
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -941,6 +941,7 @@ Function *CodeExtractor::constructFunction(const ValueSet &inputs,
case Attribute::NoSanitizeBounds:
case Attribute::NoSanitizeCoverage:
case Attribute::NullPointerIsValid:
+ case Attribute::OptimizeForDebugging:
case Attribute::OptForFuzzing:
case Attribute::OptimizeNone:
case Attribute::OptimizeForSize:
diff --git a/llvm/test/Bitcode/attributes.ll b/llvm/test/Bitcode/attributes.ll
index 9af648fe262a351..eaf670575f4dd73 100644
--- a/llvm/test/Bitcode/attributes.ll
+++ b/llvm/test/Bitcode/attributes.ll
@@ -511,6 +511,12 @@ define void @f87() fn_ret_thunk_extern { ret void }
; CHECK: define void @f88() [[SKIPPROFILE:#[0-9]+]]
define void @f88() skipprofile { ret void }
+define void @f89() optdebug
+; CHECK: define void @f89() [[OPTDEBUG:#[0-9]+]]
+{
+ ret void;
+}
+
; CHECK: attributes #0 = { noreturn }
; CHECK: attributes #1 = { nounwind }
; CHECK: attributes #2 = { memory(none) }
@@ -566,4 +572,5 @@ define void @f88() skipprofile { ret void }
; CHECK: attributes #52 = { nosanitize_bounds }
; CHECK: attributes [[FNRETTHUNKEXTERN]] = { fn_ret_thunk_extern }
; CHECK: attributes [[SKIPPROFILE]] = { skipprofile }
+; CHECK: attributes [[OPTDEBUG]] = { optdebug }
; CHECK: attributes #[[NOBUILTIN]] = { nobuiltin }
diff --git a/llvm/utils/emacs/llvm-mode.el b/llvm/utils/emacs/llvm-mode.el
index e37cc693a1940aa..53381cf91b17b90 100644
--- a/llvm/utils/emacs/llvm-mode.el
+++ b/llvm/utils/emacs/llvm-mode.el
@@ -25,7 +25,7 @@
'("alwaysinline" "argmemonly" "allocsize" "builtin" "cold" "convergent" "dereferenceable" "dereferenceable_or_null" "hot" "immarg" "inaccessiblememonly"
"inaccessiblemem_or_argmemonly" "inalloca" "inlinehint" "jumptable" "minsize" "mustprogress" "naked" "nobuiltin" "nonnull" "nocapture"
"nocallback" "nocf_check" "noduplicate" "nofree" "noimplicitfloat" "noinline" "nomerge" "nonlazybind" "noprofile" "noredzone" "noreturn"
- "norecurse" "nosync" "noundef" "nounwind" "nosanitize_bounds" "nosanitize_coverage" "null_pointer_is_valid" "optforfuzzing" "optnone" "optsize" "preallocated" "readnone" "readonly" "returned" "returns_twice"
+ "norecurse" "nosync" "noundef" "nounwind" "nosanitize_bounds" "nosanitize_coverage" "null_pointer_is_valid" "optdebug" "optforfuzzing" "optnone" "optsize" "preallocated" "readnone" "readonly" "returned" "returns_twice"
"shadowcallstack" "signext" "speculatable" "speculative_load_hardening" "ssp" "sspreq" "sspstrong" "safestack" "sanitize_address" "sanitize_hwaddress" "sanitize_memtag"
"sanitize_thread" "sanitize_memory" "strictfp" "swifterror" "uwtable" "vscale_range" "willreturn" "writeonly" "zeroext") 'symbols) . font-lock-constant-face)
;; Variables
diff --git a/llvm/utils/kate/llvm.xml b/llvm/utils/kate/llvm.xml
index 9f7ec77bf3154d4..0e7aec3880e6b4a 100644
--- a/llvm/utils/kate/llvm.xml
+++ b/llvm/utils/kate/llvm.xml
@@ -111,6 +111,7 @@
<item> nosync </item>
<item> nounwind </item>
<item> null_pointer_is_valid </item>
+ <item> optdebug </item>
<item> optforfuzzing </item>
<item> optnone </item>
<item> optsize </item>
diff --git a/llvm/utils/vim/syntax/llvm.vim b/llvm/utils/vim/syntax/llvm.vim
index 9185a029a22e570..d86e3d1ddbc27ff 100644
--- a/llvm/utils/vim/syntax/llvm.vim
+++ b/llvm/utils/vim/syntax/llvm.vim
@@ -142,6 +142,7 @@ syn keyword llvmKeyword
\ nosanitize_bounds
\ nosanitize_coverage
\ null_pointer_is_valid
+ \ optdebug
\ optforfuzzing
\ optnone
\ optsize
>From d2bac2f74c1b755e068a37ab50841b4c574a9339 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <Stephen.Tozer at Sony.com>
Date: Thu, 21 Sep 2023 14:41:44 +0100
Subject: [PATCH 2/3] Address review comments
---
llvm/docs/LangRef.rst | 10 +++++++---
llvm/lib/IR/Verifier.cpp | 11 +++++++++++
2 files changed, 18 insertions(+), 3 deletions(-)
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index b74c61d8a9aed9c..3c178aa789970f9 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1872,7 +1872,8 @@ example:
passes make choices that keep the code size of this function as small
as possible and perform optimizations that may sacrifice runtime
performance in order to minimize the size of the generated code.
- This attribute is incompatible with the ``optnone`` attribute.
+ This attribute is incompatible with the ``optdebug`` and ``optnone``
+ attributes.
``naked``
This attribute disables prologue / epilogue emission for the
function. This can have very system-specific consequences.
@@ -2029,6 +2030,8 @@ example:
This attribute suggests that optimization passes and code generator passes
should make choices that try to preserve debug info without significantly
degrading runtime performance.
+ This attribute is incompatible with the ``minsize``, ``optsize``, and
+ ``optnone`` attributes.
``optforfuzzing``
This attribute indicates that this function should be optimized
for maximum fuzzing signal.
@@ -2038,7 +2041,7 @@ example:
Code generation defaults to the "fast" instruction selector.
This attribute cannot be used together with the ``alwaysinline``
attribute; this attribute is also incompatible
- with the ``minsize`` attribute and the ``optsize`` attribute.
+ with the ``minsize``, ``optsize``, and ``optdebug`` attributes.
This attribute requires the ``noinline`` attribute to be specified on
the function as well, so the function is never inlined into any caller.
@@ -2049,7 +2052,8 @@ example:
passes make choices that keep the code size of this function low,
and otherwise do optimizations specifically to reduce code size as
long as they do not significantly impact runtime performance.
- This attribute is incompatible with the ``optnone`` attribute.
+ This attribute is incompatible with the ``optdebug`` and ``optnone``
+ attributes.
``"patchable-function"``
This attribute tells the code generator that the code
generated for this function needs to follow certain conventions that
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 5a3328416db3eb0..3c4efd7e359c524 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -2118,6 +2118,17 @@ void Verifier::verifyFunctionAttrs(FunctionType *FT, AttributeList Attrs,
Check(!Attrs.hasFnAttr(Attribute::MinSize),
"Attributes 'minsize and optnone' are incompatible!", V);
+
+ Check(!Attrs.hasFnAttr(Attribute::OptimizeForDebugging),
+ "Attributes 'optdebug and optnone' are incompatible!", V);
+ }
+
+ if (Attrs.hasFnAttr(Attribute::OptimizeForDebugging)) {
+ Check(!Attrs.hasFnAttr(Attribute::OptimizeForSize),
+ "Attributes 'optsize and optdebug' are incompatible!", V);
+
+ Check(!Attrs.hasFnAttr(Attribute::MinSize),
+ "Attributes 'minsize and optdebug' are incompatible!", V);
}
if (Attrs.hasFnAttr("aarch64_pstate_sm_enabled")) {
>From 58f171e8e46613ac86f4a7e850a0502619647eb4 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <Stephen.Tozer at Sony.com>
Date: Thu, 12 Oct 2023 16:52:18 +0100
Subject: [PATCH 3/3] Remove optdebug removal from frontend, since it is not
added yet
---
clang/lib/CodeGen/CodeGenModule.cpp | 1 -
1 file changed, 1 deletion(-)
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 875952232e24b86..b1a6683a66bd052 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2347,7 +2347,6 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
B.addAttribute(llvm::Attribute::Naked);
// OptimizeNone wins over OptimizeForSize and MinSize.
- F->removeFnAttr(llvm::Attribute::OptimizeForDebugging);
F->removeFnAttr(llvm::Attribute::OptimizeForSize);
F->removeFnAttr(llvm::Attribute::MinSize);
} else if (D->hasAttr<NakedAttr>()) {
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