[llvm-branch-commits] [llvm] 3733463 - [IR][PGO] Add hot func attribute and use hot/cold attribute in func section
Rong Xu via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Thu Dec 17 18:59:31 PST 2020
Author: Rong Xu
Date: 2020-12-17T18:41:12-08:00
New Revision: 3733463dbb58a29892be3872bd32f93cb9af492c
URL: https://github.com/llvm/llvm-project/commit/3733463dbb58a29892be3872bd32f93cb9af492c
DIFF: https://github.com/llvm/llvm-project/commit/3733463dbb58a29892be3872bd32f93cb9af492c.diff
LOG: [IR][PGO] Add hot func attribute and use hot/cold attribute in func section
Clang FE currently has hot/cold function attribute. But we only have
cold function attribute in LLVM IR.
This patch adds support of hot function attribute to LLVM IR. This
attribute will be used in setting function section prefix/suffix.
Currently .hot and .unlikely suffix only are added in PGO (Sample PGO)
compilation (through isFunctionHotInCallGraph and
isFunctionColdInCallGraph).
This patch changes the behavior. The new behavior is:
(1) If the user annotates a function as hot or isFunctionHotInCallGraph
is true, this function will be marked as hot. Otherwise,
(2) If the user annotates a function as cold or
isFunctionColdInCallGraph is true, this function will be marked as
cold.
The changes are:
(1) user annotated function attribute will used in setting function
section prefix/suffix.
(2) hot attribute overwrites profile count based hotness.
(3) profile count based hotness overwrite user annotated cold attribute.
The intention for these changes is to provide the user a way to mark
certain function as hot in cases where training input is hard to cover
all the hot functions.
Differential Revision: https://reviews.llvm.org/D92493
Added:
llvm/test/CodeGen/X86/hot-unlikely-section-prefix.ll
llvm/test/MC/AsmParser/function_hot_attr.ll
Modified:
clang/lib/CodeGen/CGCall.cpp
clang/lib/CodeGen/CodeGenModule.cpp
clang/test/CodeGen/attributes.c
llvm/docs/LangRef.rst
llvm/include/llvm/Bitcode/LLVMBitCodes.h
llvm/include/llvm/IR/Attributes.td
llvm/lib/AsmParser/LLParser.cpp
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
llvm/lib/CodeGen/CodeGenPrepare.cpp
llvm/lib/IR/Attributes.cpp
llvm/lib/IR/Verifier.cpp
llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
llvm/test/Bitcode/attributes.ll
Removed:
################################################################################
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index bfc7b8e74d8f..e28736bd3d2f 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -1944,6 +1944,8 @@ void CodeGenModule::ConstructAttributeList(
FuncAttrs.addAttribute(llvm::Attribute::NoReturn);
if (TargetDecl->hasAttr<ColdAttr>())
FuncAttrs.addAttribute(llvm::Attribute::Cold);
+ if (TargetDecl->hasAttr<HotAttr>())
+ FuncAttrs.addAttribute(llvm::Attribute::Hot);
if (TargetDecl->hasAttr<NoDuplicateAttr>())
FuncAttrs.addAttribute(llvm::Attribute::NoDuplicate);
if (TargetDecl->hasAttr<ConvergentAttr>())
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 7dd343dbcc16..93916e85a461 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1744,7 +1744,8 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
B.addAttribute(llvm::Attribute::OptimizeForSize);
B.addAttribute(llvm::Attribute::Cold);
}
-
+ if (D->hasAttr<HotAttr>())
+ B.addAttribute(llvm::Attribute::Hot);
if (D->hasAttr<MinSizeAttr>())
B.addAttribute(llvm::Attribute::MinSize);
}
diff --git a/clang/test/CodeGen/attributes.c b/clang/test/CodeGen/attributes.c
index 0c1455d3c612..5ef176c138af 100644
--- a/clang/test/CodeGen/attributes.c
+++ b/clang/test/CodeGen/attributes.c
@@ -63,6 +63,13 @@ void t72() { t71(); }
// CHECK: call void @t71() [[COLDSITE:#[0-9]+]]
// CHECK: declare void @t71() [[COLDDECL:#[0-9]+]]
+// CHECK: define void @t82() [[HOTDEF:#[0-9]+]] {
+void t81(void) __attribute__((hot));
+void t82() __attribute__((hot));
+void t82() { t81(); }
+// CHECK: call void @t81() [[HOTSITE:#[0-9]+]]
+// CHECK: declare void @t81() [[HOTDECL:#[0-9]+]]
+
// CHECK: define void @t10() [[NUW]] section "xSECT" {
void t10(void) __attribute__((section("xSECT")));
void t10(void) {}
@@ -72,6 +79,9 @@ void __attribute__((section("xSECT"))) t11(void) {}
// CHECK: define i32 @t19() [[NUW]] {
extern int t19(void) __attribute__((weak_import));
int t19(void) {
+// RUN: %clang_cc1 -emit-llvm -fcf-protection=branch -triple i386-linux-gnu -o %t %s
+// RUN: %clang_cc1 -emit-llvm -fcf-protection=branch -triple i386-linux-gnu -o %t %s
+// RUN: %clang_cc1 -emit-llvm -fcf-protection=branch -triple i386-linux-gnu -o %t %s
return 10;
}
@@ -111,6 +121,9 @@ void t24(f_t f1) {
// CHECK: attributes [[NR]] = { noinline noreturn nounwind{{.*}} }
// CHECK: attributes [[COLDDEF]] = { cold {{.*}}}
// CHECK: attributes [[COLDDECL]] = { cold {{.*}}}
+// CHECK: attributes [[HOTDEF]] = { hot {{.*}}}
+// CHECK: attributes [[HOTDECL]] = { hot {{.*}}}
// CHECK: attributes [[NOCF_CHECK_FUNC]] = { nocf_check {{.*}}}
// CHECK: attributes [[COLDSITE]] = { cold {{.*}}}
+// CHECK: attributes [[HOTSITE]] = { hot {{.*}}}
// CHECK: attributes [[NOCF_CHECK_CALL]] = { nocf_check }
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 9ba6a21d08c2..4102b5d41c05 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1496,6 +1496,15 @@ example:
can prove that the function does not execute any convergent operations.
Similarly, the optimizer may remove ``convergent`` on calls/invokes when it
can prove that the call/invoke cannot call a convergent function.
+``hot``
+ This attribute indicates that this function is a hot spot of the program
+ execution. The function will be optimized more aggressively and will be
+ placed into special subsection of the text section to improving locality.
+
+ When profile feedback is enabled, this attribute has the precedence over
+ the profile information. By marking a function ``hot``, users can work
+ around the cases where the training input does not have good coverage
+ on all the hot functions.
``inaccessiblememonly``
This attribute indicates that the function may only access memory that
is not accessible by the module being compiled. This is a weaker form
diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
index a6d28024e2e5..ef1fa85acc80 100644
--- a/llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -654,6 +654,7 @@ enum AttributeKindCodes {
ATTR_KIND_BYREF = 69,
ATTR_KIND_MUSTPROGRESS = 70,
ATTR_KIND_NO_CALLBACK = 71,
+ ATTR_KIND_HOT = 72,
};
enum ComdatSelectionKindCodes {
diff --git a/llvm/include/llvm/IR/Attributes.td b/llvm/include/llvm/IR/Attributes.td
index 798e4544aef4..45460742bf3f 100644
--- a/llvm/include/llvm/IR/Attributes.td
+++ b/llvm/include/llvm/IR/Attributes.td
@@ -63,6 +63,9 @@ def Cold : EnumAttr<"cold">;
/// Can only be moved to control-equivalent blocks.
def Convergent : EnumAttr<"convergent">;
+/// Marks function as being in a hot path and frequently called.
+def Hot: EnumAttr<"hot">;
+
/// Pointer is known to be dereferenceable.
def Dereferenceable : IntAttr<"dereferenceable">;
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 0c2c10700d78..81469300651d 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -1340,6 +1340,7 @@ bool LLParser::parseFnAttributeValuePairs(AttrBuilder &B,
case lltok::kw_argmemonly: B.addAttribute(Attribute::ArgMemOnly); break;
case lltok::kw_builtin: B.addAttribute(Attribute::Builtin); break;
case lltok::kw_cold: B.addAttribute(Attribute::Cold); break;
+ case lltok::kw_hot: B.addAttribute(Attribute::Hot); break;
case lltok::kw_convergent: B.addAttribute(Attribute::Convergent); break;
case lltok::kw_inaccessiblememonly:
B.addAttribute(Attribute::InaccessibleMemOnly); break;
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 43e4fca007c6..6146b43d5600 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1539,6 +1539,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
return Attribute::ByRef;
case bitc::ATTR_KIND_MUSTPROGRESS:
return Attribute::MustProgress;
+ case bitc::ATTR_KIND_HOT:
+ return Attribute::Hot;
}
}
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 5b965186daa8..b6a2e0b6751f 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -626,6 +626,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
return bitc::ATTR_KIND_IN_ALLOCA;
case Attribute::Cold:
return bitc::ATTR_KIND_COLD;
+ case Attribute::Hot:
+ return bitc::ATTR_KIND_HOT;
case Attribute::InaccessibleMemOnly:
return bitc::ATTR_KIND_INACCESSIBLEMEM_ONLY;
case Attribute::InaccessibleMemOrArgMemOnly:
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 8fe5cb9faba4..ec3a7e7982b2 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -472,9 +472,17 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
OptSize = F.hasOptSize();
if (ProfileGuidedSectionPrefix) {
- if (PSI->isFunctionHotInCallGraph(&F, *BFI))
+ // The hot attribute overwrites profile count based hotness while profile
+ // counts based hotness overwrite the cold attribute.
+ // This is a conservative behabvior.
+ if (F.hasFnAttribute(Attribute::Hot) ||
+ PSI->isFunctionHotInCallGraph(&F, *BFI))
F.setSectionPrefix("hot");
- else if (PSI->isFunctionColdInCallGraph(&F, *BFI))
+ // If PSI shows this function is not hot, we will placed the function
+ // into unlikely section if (1) PSI shows this is a cold function, or
+ // (2) the function has a attribute of cold.
+ else if (PSI->isFunctionColdInCallGraph(&F, *BFI) ||
+ F.hasFnAttribute(Attribute::Cold))
F.setSectionPrefix("unlikely");
else if (ProfileUnknownInSpecialSection && PSI->hasPartialSampleProfile() &&
PSI->isFunctionHotnessUnknown(F))
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index de0bc677af21..7001ab82331d 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -449,6 +449,8 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
return "zeroext";
if (hasAttribute(Attribute::Cold))
return "cold";
+ if (hasAttribute(Attribute::Hot))
+ return "hot";
if (hasAttribute(Attribute::ImmArg))
return "immarg";
if (hasAttribute(Attribute::NoUndef))
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index cac5df81661c..aeca166a6023 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -1626,6 +1626,7 @@ static bool isFuncOnlyAttr(Attribute::AttrKind Kind) {
case Attribute::Builtin:
case Attribute::NoBuiltin:
case Attribute::Cold:
+ case Attribute::Hot:
case Attribute::OptForFuzzing:
case Attribute::OptimizeNone:
case Attribute::JumpTable:
diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index 8627e8239b2e..68a313d49325 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -1921,6 +1921,17 @@ static bool annotateAllFunctions(
<< "\n");
}
for (auto &F : ColdFunctions) {
+ // Only set when there is no Attribute::Hot set by the user. For Hot
+ // attribute, user's annotation has the precedence over the profile.
+ if (F->hasFnAttribute(Attribute::Hot)) {
+ auto &Ctx = M.getContext();
+ std::string Msg = std::string("Function ") + F->getName().str() +
+ std::string(" is annotated as a hot function but"
+ " the profile is cold");
+ Ctx.diagnose(
+ DiagnosticInfoPGOProfile(M.getName().data(), Msg, DS_Warning));
+ continue;
+ }
F->addFnAttr(Attribute::Cold);
LLVM_DEBUG(dbgs() << "Set cold attribute to function: " << F->getName()
<< "\n");
diff --git a/llvm/test/Bitcode/attributes.ll b/llvm/test/Bitcode/attributes.ll
index 7db9dbe8f89e..089180ed4725 100644
--- a/llvm/test/Bitcode/attributes.ll
+++ b/llvm/test/Bitcode/attributes.ll
@@ -410,6 +410,18 @@ define void @f69() nocallback
ret void
}
+; CHECK: define void @f70() #43
+define void @f70() cold
+{
+ ret void
+}
+
+; CHECK: define void @f71() #44
+define void @f71() hot
+{
+ ret void
+}
+
; CHECK: attributes #0 = { noreturn }
; CHECK: attributes #1 = { nounwind }
; CHECK: attributes #2 = { readnone }
@@ -453,4 +465,6 @@ define void @f69() nocallback
; CHECK: attributes #40 = { null_pointer_is_valid }
; CHECK: attributes #41 = { mustprogress }
; CHECK: attributes #42 = { nocallback }
+; CHECK: attributes #43 = { cold }
+; CHECK: attributes #44 = { hot }
; CHECK: attributes #[[NOBUILTIN]] = { nobuiltin }
diff --git a/llvm/test/CodeGen/X86/hot-unlikely-section-prefix.ll b/llvm/test/CodeGen/X86/hot-unlikely-section-prefix.ll
new file mode 100644
index 000000000000..719b40d8574d
--- /dev/null
+++ b/llvm/test/CodeGen/X86/hot-unlikely-section-prefix.ll
@@ -0,0 +1,101 @@
+; Test hot or unlikely section postfix based on profile and user annotation.
+; RUN: llc < %s | FileCheck %s
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: inlinehint norecurse nounwind readnone uwtable
+define dso_local i32 @hot1() #0 !prof !31 {
+entry:
+ ret i32 1
+}
+; CHECK: .section .text.hot.,"ax", at progbits
+; CHECK: .globl hot1
+
+; Function Attrs: cold norecurse nounwind readnone uwtable
+define dso_local i32 @cold1() #1 !prof !32 {
+entry:
+ ret i32 1
+}
+; CHECK: .section .text.unlikely.,"ax", at progbits
+; CHECK: .globl cold1
+
+; Function Attrs: cold inlinehint noinline norecurse nounwind optsize readnone uwtable
+define dso_local i32 @hot2() #2 !prof !31 {
+entry:
+ ret i32 1
+}
+; CHECK: .section .text.hot.,"ax", at progbits
+; CHECK: .globl hot2
+
+define dso_local i32 @normal() {
+entry:
+ ret i32 1
+}
+; CHECK: text
+; CHECK: .globl normal
+
+; Function Attrs: hot noinline norecurse nounwind readnone uwtable
+define dso_local i32 @hot3() #3 !prof !32 {
+entry:
+ ret i32 1
+}
+; CHECK: .section .text.hot.,"ax", at progbits
+; CHECK: .globl hot3
+
+; Function Attrs: cold noinline norecurse nounwind optsize readnone uwtable
+define dso_local i32 @cold2() #4 {
+entry:
+ ret i32 1
+}
+; CHECK: .section .text.unlikely.,"ax", at progbits
+; CHECK: .globl cold2
+
+; Function Attrs: hot noinline norecurse nounwind readnone uwtable
+define dso_local i32 @hot4() #3 {
+entry:
+ ret i32 1
+}
+; CHECK: .section .text.hot.,"ax", at progbits
+; CHECK: .globl hot4
+
+attributes #0 = { inlinehint norecurse nounwind readnone uwtable }
+attributes #1 = { cold norecurse nounwind readnone uwtable }
+attributes #2 = { cold inlinehint noinline norecurse nounwind optsize readnone uwtable }
+attributes #3 = { hot noinline norecurse nounwind readnone uwtable }
+attributes #4 = { cold noinline norecurse nounwind optsize readnone uwtable }
+
+!llvm.module.flags = !{!0, !1}
+!llvm.ident = !{!30}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{i32 1, !"ProfileSummary", !2}
+!2 = !{!3, !4, !5, !6, !7, !8, !9, !10, !11, !12}
+!3 = !{!"ProfileFormat", !"InstrProf"}
+!4 = !{!"TotalCount", i64 402020}
+!5 = !{!"MaxCount", i64 200000}
+!6 = !{!"MaxInternalCount", i64 2000}
+!7 = !{!"MaxFunctionCount", i64 200000}
+!8 = !{!"NumCounts", i64 7}
+!9 = !{!"NumFunctions", i64 5}
+!10 = !{!"IsPartialProfile", i64 0}
+!11 = !{!"PartialProfileRatio", double 0.000000e+00}
+!12 = !{!"DetailedSummary", !13}
+!13 = !{!14, !15, !16, !17, !18, !19, !20, !21, !22, !23, !24, !25, !26, !27, !28, !29}
+!14 = !{i32 10000, i64 200000, i32 1}
+!15 = !{i32 100000, i64 200000, i32 1}
+!16 = !{i32 200000, i64 200000, i32 1}
+!17 = !{i32 300000, i64 200000, i32 1}
+!18 = !{i32 400000, i64 200000, i32 1}
+!19 = !{i32 500000, i64 100000, i32 3}
+!20 = !{i32 600000, i64 100000, i32 3}
+!21 = !{i32 700000, i64 100000, i32 3}
+!22 = !{i32 800000, i64 100000, i32 3}
+!23 = !{i32 900000, i64 100000, i32 3}
+!24 = !{i32 950000, i64 100000, i32 3}
+!25 = !{i32 990000, i64 100000, i32 3}
+!26 = !{i32 999000, i64 2000, i32 4}
+!27 = !{i32 999900, i64 2000, i32 4}
+!28 = !{i32 999990, i64 10, i32 6}
+!29 = !{i32 999999, i64 10, i32 6}
+!30 = !{!"clang version 12.0.0 (https://github.com/llvm/llvm-project.git 53c5fdd59a5cf7fbb4dcb7a7e84c9c4a40d32a84)"}
+!31 = !{!"function_entry_count", i64 100000}
+!32 = !{!"function_entry_count", i64 10}
diff --git a/llvm/test/MC/AsmParser/function_hot_attr.ll b/llvm/test/MC/AsmParser/function_hot_attr.ll
new file mode 100644
index 000000000000..1bfda26d8fa8
--- /dev/null
+++ b/llvm/test/MC/AsmParser/function_hot_attr.ll
@@ -0,0 +1,13 @@
+; Test hot function attribute
+; RUN: llc < %s | FileCheck %s
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: hot noinline norecurse nounwind readnone uwtable
+define dso_local i32 @hot4() #0 {
+entry:
+ ret i32 1
+}
+; CHECK: .section .text.hot.,"ax", at progbits
+; CHECK: .globl hot4
+
+attributes #0 = { hot noinline norecurse nounwind readnone uwtable }
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