[llvm] a8874cf - [llvm][IR] Add per-global code model attribute (#72077)
via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 4 17:42:58 PST 2023
Author: hev
Date: 2023-12-05T09:42:53+08:00
New Revision: a8874cf50bb676facb4429234dff7774e579faef
URL: https://github.com/llvm/llvm-project/commit/a8874cf50bb676facb4429234dff7774e579faef
DIFF: https://github.com/llvm/llvm-project/commit/a8874cf50bb676facb4429234dff7774e579faef.diff
LOG: [llvm][IR] Add per-global code model attribute (#72077)
This adds a per-global code model attribute, which can override the
target's code model to access global variables.
Suggested-by: Arthur Eubanks <aeubanks at google.com>
Link: https://discourse.llvm.org/t/how-to-best-implement-code-model-overriding-for-certain-values/71816
Link: https://discourse.llvm.org/t/rfc-add-per-global-code-model-attribute/74944
Added:
llvm/test/Transforms/GlobalOpt/globalvar-code-model.ll
Modified:
llvm/docs/LangRef.rst
llvm/include/llvm/AsmParser/LLParser.h
llvm/include/llvm/AsmParser/LLToken.h
llvm/include/llvm/IR/GlobalObject.h
llvm/include/llvm/IR/GlobalVariable.h
llvm/lib/AsmParser/LLLexer.cpp
llvm/lib/AsmParser/LLParser.cpp
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
llvm/lib/IR/AsmWriter.cpp
llvm/lib/IR/Globals.cpp
llvm/test/Assembler/globalvariable-attributes.ll
Removed:
################################################################################
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 4bd19a332d8d8..cf9b33a30eab5 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -705,6 +705,13 @@ information. Attaching section information to an external declaration is an
assertion that its definition is located in the specified section. If the
definition is located in a
diff erent section, the behavior is undefined.
+LLVM allows an explicit code model to be specified for globals. If the
+target supports it, it will emit globals in the code model specified,
+overriding the code model used to compile the translation unit.
+The allowed values are "tiny", "small", "kernel", "medium", "large".
+This may be extended in the future to specify global data layout that
+doesn't cleanly fit into a specific code model.
+
By default, global initializers are optimized by assuming that global
variables defined within the module are not modified from their
initial values before the start of the global initializer. This is
@@ -761,6 +768,7 @@ Syntax::
<global | constant> <Type> [<InitializerConstant>]
[, section "name"] [, partition "name"]
[, comdat [($name)]] [, align <Alignment>]
+ [, code_model "model"]
[, no_sanitize_address] [, no_sanitize_hwaddress]
[, sanitize_address_dyninit] [, sanitize_memtag]
(, !name !N)*
@@ -778,6 +786,13 @@ The following example just declares a global variable
@G = external global i32
+The following example defines a global variable with the
+``large`` code model:
+
+.. code-block:: llvm
+
+ @G = internal global i32 0, code_model "large"
+
The following example defines a thread-local global with the
``initialexec`` TLS model:
diff --git a/llvm/include/llvm/AsmParser/LLParser.h b/llvm/include/llvm/AsmParser/LLParser.h
index 810f3668d05d4..793287c772b55 100644
--- a/llvm/include/llvm/AsmParser/LLParser.h
+++ b/llvm/include/llvm/AsmParser/LLParser.h
@@ -290,6 +290,7 @@ namespace llvm {
bool parseOptionalCallingConv(unsigned &CC);
bool parseOptionalAlignment(MaybeAlign &Alignment,
bool AllowParens = false);
+ bool parseOptionalCodeModel(CodeModel::Model &model);
bool parseOptionalDerefAttrBytes(lltok::Kind AttrKind, uint64_t &Bytes);
bool parseOptionalUWTableKind(UWTableKind &Kind);
bool parseAllocKind(AllocFnKind &Kind);
diff --git a/llvm/include/llvm/AsmParser/LLToken.h b/llvm/include/llvm/AsmParser/LLToken.h
index 0683291faae72..0aa0093e8efbd 100644
--- a/llvm/include/llvm/AsmParser/LLToken.h
+++ b/llvm/include/llvm/AsmParser/LLToken.h
@@ -116,6 +116,7 @@ enum Kind {
kw_addrspace,
kw_section,
kw_partition,
+ kw_code_model,
kw_alias,
kw_ifunc,
kw_module,
diff --git a/llvm/include/llvm/IR/GlobalObject.h b/llvm/include/llvm/IR/GlobalObject.h
index 889bd3a28e12b..ae8e616824448 100644
--- a/llvm/include/llvm/IR/GlobalObject.h
+++ b/llvm/include/llvm/IR/GlobalObject.h
@@ -51,6 +51,7 @@ class GlobalObject : public GlobalValue {
Comdat *ObjComdat = nullptr;
enum {
LastAlignmentBit = 5,
+ LastCodeModelBit = 8,
HasSectionHashEntryBit,
GlobalObjectBits,
diff --git a/llvm/include/llvm/IR/GlobalVariable.h b/llvm/include/llvm/IR/GlobalVariable.h
index 5ddffd16acc68..bcaf8e91432ba 100644
--- a/llvm/include/llvm/IR/GlobalVariable.h
+++ b/llvm/include/llvm/IR/GlobalVariable.h
@@ -47,6 +47,11 @@ class GlobalVariable : public GlobalObject, public ilist_node<GlobalVariable> {
// global initializers are run?
bool isExternallyInitializedConstant : 1;
+private:
+ static const unsigned CodeModelBits = LastCodeModelBit - LastAlignmentBit;
+ static const unsigned CodeModelMask = (1 << CodeModelBits) - 1;
+ static const unsigned CodeModelShift = LastAlignmentBit + 1;
+
public:
/// GlobalVariable ctor - If a parent module is specified, the global is
/// automatically inserted into the end of the specified modules global list.
@@ -247,6 +252,28 @@ class GlobalVariable : public GlobalObject, public ilist_node<GlobalVariable> {
getAttributes().hasAttribute("rodata-section");
}
+ /// Get the custom code model raw value of this global.
+ ///
+ unsigned getCodeModelRaw() const {
+ unsigned Data = getGlobalValueSubClassData();
+ return (Data >> CodeModelShift) & CodeModelMask;
+ }
+
+ /// Get the custom code model of this global if it has one.
+ ///
+ /// If this global does not have a custom code model, the empty instance
+ /// will be returned.
+ std::optional<CodeModel::Model> getCodeModel() const {
+ unsigned CodeModelData = getCodeModelRaw();
+ if (CodeModelData > 0)
+ return static_cast<CodeModel::Model>(CodeModelData - 1);
+ return {};
+ }
+
+ /// Change the code model for this global.
+ ///
+ void setCodeModel(CodeModel::Model CM);
+
// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const Value *V) {
return V->getValueID() == Value::GlobalVariableVal;
diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 09a205c445dbe..bf01b39e6f971 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -571,6 +571,7 @@ lltok::Kind LLLexer::LexIdentifier() {
KEYWORD(addrspace);
KEYWORD(section);
KEYWORD(partition);
+ KEYWORD(code_model);
KEYWORD(alias);
KEYWORD(ifunc);
KEYWORD(module);
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index d236b6cfa9000..0e962e7f6daac 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -1286,6 +1286,11 @@ bool LLParser::parseGlobal(const std::string &Name, LocTy NameLoc,
return true;
if (Alignment)
GV->setAlignment(*Alignment);
+ } else if (Lex.getKind() == lltok::kw_code_model) {
+ CodeModel::Model CodeModel;
+ if (parseOptionalCodeModel(CodeModel))
+ return true;
+ GV->setCodeModel(CodeModel);
} else if (Lex.getKind() == lltok::MetadataVar) {
if (parseGlobalObjectMetadataAttachment(*GV))
return true;
@@ -2168,6 +2173,30 @@ bool LLParser::parseOptionalAlignment(MaybeAlign &Alignment, bool AllowParens) {
return false;
}
+/// parseOptionalCodeModel
+/// ::= /* empty */
+/// ::= 'code_model' "large"
+bool LLParser::parseOptionalCodeModel(CodeModel::Model &model) {
+ Lex.Lex();
+ auto StrVal = Lex.getStrVal();
+ auto ErrMsg = "expected global code model string";
+ if (StrVal == "tiny")
+ model = CodeModel::Tiny;
+ else if (StrVal == "small")
+ model = CodeModel::Small;
+ else if (StrVal == "kernel")
+ model = CodeModel::Kernel;
+ else if (StrVal == "medium")
+ model = CodeModel::Medium;
+ else if (StrVal == "large")
+ model = CodeModel::Large;
+ else
+ return tokError(ErrMsg);
+ if (parseToken(lltok::StringConstant, ErrMsg))
+ return true;
+ return false;
+}
+
/// parseOptionalDerefAttrBytes
/// ::= /* empty */
/// ::= AttrKind '(' 4 ')'
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index e4c3770946b3a..71417bf5086c1 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1144,6 +1144,23 @@ static bool getDecodedDSOLocal(unsigned Val) {
}
}
+static std::optional<CodeModel::Model> getDecodedCodeModel(unsigned Val) {
+ switch (Val) {
+ case 1:
+ return CodeModel::Tiny;
+ case 2:
+ return CodeModel::Small;
+ case 3:
+ return CodeModel::Kernel;
+ case 4:
+ return CodeModel::Medium;
+ case 5:
+ return CodeModel::Large;
+ }
+
+ return {};
+}
+
static GlobalVariable::ThreadLocalMode getDecodedThreadLocalMode(unsigned Val) {
switch (Val) {
case 0: return GlobalVariable::NotThreadLocal;
@@ -3805,6 +3822,7 @@ Error BitcodeReader::parseGlobalVarRecord(ArrayRef<uint64_t> Record) {
// dllstorageclass, comdat, attributes, preemption specifier,
// partition strtab offset, partition strtab size] (name in VST)
// v2: [strtab_offset, strtab_size, v1]
+ // v3: [v2, code_model]
StringRef Name;
std::tie(Name, Record) = readNameFromStrtab(Record);
@@ -3913,6 +3931,13 @@ Error BitcodeReader::parseGlobalVarRecord(ArrayRef<uint64_t> Record) {
NewGV->setSanitizerMetadata(Meta);
}
+ if (Record.size() > 17 && Record[17]) {
+ if (auto CM = getDecodedCodeModel(Record[17]))
+ NewGV->setCodeModel(*CM);
+ else
+ return error("Invalid global variable code model");
+ }
+
return Error::success();
}
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 8239775d04865..4969809b85866 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -1403,7 +1403,7 @@ void ModuleBitcodeWriter::writeModuleInfo() {
// GLOBALVAR: [strtab offset, strtab size, type, isconst, initid,
// linkage, alignment, section, visibility, threadlocal,
// unnamed_addr, externally_initialized, dllstorageclass,
- // comdat, attributes, DSO_Local, GlobalSanitizer]
+ // comdat, attributes, DSO_Local, GlobalSanitizer, code_model]
Vals.push_back(addToStrtab(GV.getName()));
Vals.push_back(GV.getName().size());
Vals.push_back(VE.getTypeID(GV.getValueType()));
@@ -1420,7 +1420,7 @@ void ModuleBitcodeWriter::writeModuleInfo() {
GV.isExternallyInitialized() ||
GV.getDLLStorageClass() != GlobalValue::DefaultStorageClass ||
GV.hasComdat() || GV.hasAttributes() || GV.isDSOLocal() ||
- GV.hasPartition() || GV.hasSanitizerMetadata()) {
+ GV.hasPartition() || GV.hasSanitizerMetadata() || GV.getCodeModel()) {
Vals.push_back(getEncodedVisibility(GV));
Vals.push_back(getEncodedThreadLocalMode(GV));
Vals.push_back(getEncodedUnnamedAddr(GV));
@@ -1438,6 +1438,7 @@ void ModuleBitcodeWriter::writeModuleInfo() {
Vals.push_back((GV.hasSanitizerMetadata() ? serializeSanitizerMetadata(
GV.getSanitizerMetadata())
: 0));
+ Vals.push_back(GV.getCodeModelRaw());
} else {
AbbrevToUse = SimpleGVarAbbrev;
}
diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index fabc79adbd33d..c67c32a28e0d6 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -3672,6 +3672,27 @@ void AssemblyWriter::printGlobal(const GlobalVariable *GV) {
printEscapedString(GV->getPartition(), Out);
Out << '"';
}
+ if (auto CM = GV->getCodeModel()) {
+ Out << ", code_model \"";
+ switch (*CM) {
+ case CodeModel::Tiny:
+ Out << "tiny";
+ break;
+ case CodeModel::Small:
+ Out << "small";
+ break;
+ case CodeModel::Kernel:
+ Out << "kernel";
+ break;
+ case CodeModel::Medium:
+ Out << "medium";
+ break;
+ case CodeModel::Large:
+ Out << "large";
+ break;
+ }
+ Out << '"';
+ }
using SanitizerMetadata = llvm::GlobalValue::SanitizerMetadata;
if (GV->hasSanitizerMetadata()) {
diff --git a/llvm/lib/IR/Globals.cpp b/llvm/lib/IR/Globals.cpp
index 7bd4503a689e4..51bdbeb0abf2c 100644
--- a/llvm/lib/IR/Globals.cpp
+++ b/llvm/lib/IR/Globals.cpp
@@ -482,6 +482,8 @@ void GlobalVariable::copyAttributesFrom(const GlobalVariable *Src) {
GlobalObject::copyAttributesFrom(Src);
setExternallyInitialized(Src->isExternallyInitialized());
setAttributes(Src->getAttributes());
+ if (auto CM = Src->getCodeModel())
+ setCodeModel(*CM);
}
void GlobalVariable::dropAllReferences() {
@@ -489,6 +491,15 @@ void GlobalVariable::dropAllReferences() {
clearMetadata();
}
+void GlobalVariable::setCodeModel(CodeModel::Model CM) {
+ unsigned CodeModelData = static_cast<unsigned>(CM) + 1;
+ unsigned OldData = getGlobalValueSubClassData();
+ unsigned NewData = (OldData & ~(CodeModelMask << CodeModelShift)) |
+ (CodeModelData << CodeModelShift);
+ setGlobalValueSubClassData(NewData);
+ assert(getCodeModel() == CM && "Code model representation error!");
+}
+
//===----------------------------------------------------------------------===//
// GlobalAlias Implementation
//===----------------------------------------------------------------------===//
diff --git a/llvm/test/Assembler/globalvariable-attributes.ll b/llvm/test/Assembler/globalvariable-attributes.ll
index 544f9bdb270e9..4882b447973c0 100644
--- a/llvm/test/Assembler/globalvariable-attributes.ll
+++ b/llvm/test/Assembler/globalvariable-attributes.ll
@@ -9,6 +9,11 @@
@g7 = global i32 2, sanitize_address_dyninit, align 4
@g8 = global i32 2, sanitize_memtag, align 4
@g9 = global i32 2, no_sanitize_address, no_sanitize_hwaddress, sanitize_memtag, align 4
+ at g10 = global i32 2, code_model "tiny"
+ at g11 = global i32 2, code_model "small"
+ at g12 = global i32 2, code_model "kernel"
+ at g13 = global i32 2, code_model "medium"
+ at g14 = global i32 2, code_model "large"
attributes #0 = { "string" = "value" nobuiltin norecurse }
@@ -21,6 +26,11 @@ attributes #0 = { "string" = "value" nobuiltin norecurse }
; CHECK: @g7 = global i32 2, sanitize_address_dyninit, align 4
; CHECK: @g8 = global i32 2, sanitize_memtag, align 4
; CHECK: @g9 = global i32 2, no_sanitize_address, no_sanitize_hwaddress, sanitize_memtag, align 4
+; CHECK: @g10 = global i32 2, code_model "tiny"
+; CHECK: @g11 = global i32 2, code_model "small"
+; CHECK: @g12 = global i32 2, code_model "kernel"
+; CHECK: @g13 = global i32 2, code_model "medium"
+; CHECK: @g14 = global i32 2, code_model "large"
; CHECK: attributes #0 = { "key"="value" "key2"="value2" }
; CHECK: attributes #1 = { "key3"="value3" }
diff --git a/llvm/test/Transforms/GlobalOpt/globalvar-code-model.ll b/llvm/test/Transforms/GlobalOpt/globalvar-code-model.ll
new file mode 100644
index 0000000000000..276a49474f73f
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/globalvar-code-model.ll
@@ -0,0 +1,11 @@
+; RUN: opt -passes=globalopt -S < %s | FileCheck %s
+
+ at G = internal global i32 5, code_model "large"
+
+define i32 @test() norecurse {
+ %a = load i32, ptr @G
+ store i32 4, ptr @G
+ ret i32 %a
+}
+
+; CHECK: @G = internal unnamed_addr global i1 false, code_model "large"
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