[llvm] [BasicBlockSections] Always keep the entry block in the beginning of the function. (PR #74696)
Rahman Lavaee via llvm-commits
llvm-commits at lists.llvm.org
Wed Dec 6 21:07:28 PST 2023
https://github.com/rlavaee created https://github.com/llvm/llvm-project/pull/74696
BasicBlockSections must enforce placing the entry block at the beginning of the function regardless of the basic block sections profile.
>From 383082166dde8ca208fcb2732810c017630c301d Mon Sep 17 00:00:00 2001
From: Rahman Lavaee <rahmanl at google.com>
Date: Wed, 6 Dec 2023 23:17:39 +0000
Subject: [PATCH] [BasicBlockSections] Always keep the entry block in the
beginning of the function.
BasicBlockSections must enforce placing the entry block at the beginning
of the function regardless of the basic block sections profile.
---
llvm/include/llvm/CodeGen/MachineBasicBlock.h | 4 +-
llvm/lib/CodeGen/BasicBlockSections.cpp | 8 ++--
.../BasicBlockSectionsProfileReader.cpp | 7 ---
.../basic-block-sections-clusters-error.ll | 6 +--
.../X86/basic-block-sections-entryblock.ll | 43 +++++++++++++++++++
5 files changed, 51 insertions(+), 17 deletions(-)
create mode 100644 llvm/test/CodeGen/X86/basic-block-sections-entryblock.ll
diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index 5812295f73b5a..c84fd281c6a54 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -74,10 +74,10 @@ struct MBBSectionID {
MBBSectionID(SectionType T) : Type(T), Number(0) {}
};
-// This structure represents the information for a basic block.
+// This structure represents the information for a basic block pertaining to
+// the basic block sections profile.
struct UniqueBBID {
unsigned BaseID;
- // sections profile).
unsigned CloneID;
};
diff --git a/llvm/lib/CodeGen/BasicBlockSections.cpp b/llvm/lib/CodeGen/BasicBlockSections.cpp
index 42997d2287d61..4b7a2698afc8c 100644
--- a/llvm/lib/CodeGen/BasicBlockSections.cpp
+++ b/llvm/lib/CodeGen/BasicBlockSections.cpp
@@ -318,9 +318,8 @@ bool BasicBlockSections::runOnMachineFunction(MachineFunction &MF) {
MF.setBBSectionsType(BBSectionsType);
assignSections(MF, FuncClusterInfo);
- // We make sure that the cluster including the entry basic block precedes all
- // other clusters.
- auto EntryBBSectionID = MF.front().getSectionID();
+ const MachineBasicBlock &EntryBB = MF.front();
+ auto EntryBBSectionID = EntryBB.getSectionID();
// Helper function for ordering BB sections as follows:
// * Entry section (section including the entry block).
@@ -347,6 +346,9 @@ bool BasicBlockSections::runOnMachineFunction(MachineFunction &MF) {
auto YSectionID = Y.getSectionID();
if (XSectionID != YSectionID)
return MBBSectionOrder(XSectionID, YSectionID);
+ // Make sure that the entry block is placed at the beginning.
+ if (&X == &EntryBB || &Y == &EntryBB)
+ return &X == &EntryBB;
// If the two basic block are in the same section, the order is decided by
// their position within the section.
if (XSectionID.Type == MBBSectionID::SectionType::Default)
diff --git a/llvm/lib/CodeGen/BasicBlockSectionsProfileReader.cpp b/llvm/lib/CodeGen/BasicBlockSectionsProfileReader.cpp
index 96662378a8693..c544171e2abb1 100644
--- a/llvm/lib/CodeGen/BasicBlockSectionsProfileReader.cpp
+++ b/llvm/lib/CodeGen/BasicBlockSectionsProfileReader.cpp
@@ -213,10 +213,6 @@ Error BasicBlockSectionsProfileReader::ReadV1Profile() {
Twine("duplicate basic block id found '") + BasicBlockIDStr +
"'");
- if (!BasicBlockID->BaseID && CurrentPosition)
- return createProfileParseError(
- "entry BB (0) does not begin a cluster.");
-
FI->second.ClusterInfo.emplace_back(BBClusterInfo{
*std::move(BasicBlockID), CurrentCluster, CurrentPosition++});
}
@@ -287,9 +283,6 @@ Error BasicBlockSectionsProfileReader::ReadV0Profile() {
if (!FuncBBIDs.insert(BBID).second)
return createProfileParseError(
Twine("duplicate basic block id found '") + BBIDStr + "'");
- if (BBID == 0 && CurrentPosition)
- return createProfileParseError(
- "entry BB (0) does not begin a cluster");
FI->second.ClusterInfo.emplace_back(
BBClusterInfo({{static_cast<unsigned>(BBID), 0},
diff --git a/llvm/test/CodeGen/X86/basic-block-sections-clusters-error.ll b/llvm/test/CodeGen/X86/basic-block-sections-clusters-error.ll
index 597d8f6707ecc..d6f3d5010b556 100644
--- a/llvm/test/CodeGen/X86/basic-block-sections-clusters-error.ll
+++ b/llvm/test/CodeGen/X86/basic-block-sections-clusters-error.ll
@@ -5,10 +5,6 @@
; RUN: echo '!!1' >> %t1
; RUN: not --crash llc < %s -O0 -mtriple=x86_64-pc-linux -function-sections -basic-block-sections=%t1 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR1
; CHECK-ERROR1: LLVM ERROR: invalid profile {{.*}} at line 3: duplicate basic block id found '1'
-; RUN: echo '!dummy1' > %t2
-; RUN: echo '!!4 0' >> %t2
-; RUN: not --crash llc < %s -O0 -mtriple=x86_64-pc-linux -function-sections -basic-block-sections=%t2 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR2
-; CHECK-ERROR2: LLVM ERROR: invalid profile {{.*}} at line 2: entry BB (0) does not begin a cluster
; RUN: echo '!dummy1' > %t3
; RUN: echo '!!-1' >> %t3
; RUN: not --crash llc < %s -O0 -mtriple=x86_64-pc-linux -function-sections -basic-block-sections=%t3 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR3
@@ -48,7 +44,7 @@
; RUN: echo 'f dummy1' >> %t11
; RUN: echo 'c 0 1.a' >> %t11
; RUN: not --crash llc < %s -O0 -mtriple=x86_64 -function-sections -basic-block-sections=%t11 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR11
-; CHECK-ERROR11: LLVM ERROR: invalid profile {{.*}} at line 3: unable to parse clone id: 'a'
+; CHECK-ERROR11: LLVM ERROR: invalid profile {{.*}} at line 3: unable to parse clone id: 'a'
; RUN: echo 'v1' > %t12
; RUN: echo 'f dummy1' >> %t12
; RUN: echo 'c 0 1' >> %t12
diff --git a/llvm/test/CodeGen/X86/basic-block-sections-entryblock.ll b/llvm/test/CodeGen/X86/basic-block-sections-entryblock.ll
new file mode 100644
index 0000000000000..349015e1403df
--- /dev/null
+++ b/llvm/test/CodeGen/X86/basic-block-sections-entryblock.ll
@@ -0,0 +1,43 @@
+; COM: Tests to verify that the entry basic block is always placed at the beginning of its section.
+; RUN: echo 'v1' > %t1
+; RUN: echo 'f foo' >> %t1
+; RUN: echo 'c2 0' >> %t1
+; RUN: llc < %s -mtriple=x86_64-pc-linux -function-sections -basic-block-sections=%t1 -O0 | FileCheck %s -check-prefix=LINUX-SECTIONS1
+
+; RUN: echo 'v1' > %t2
+; RUN: echo 'f foo' >> %t2
+; RUN: echo 'c2' >> %t2
+; RUN: llc < %s -mtriple=x86_64-pc-linux -function-sections -basic-block-sections=%t2 -O0 | FileCheck %s -check-prefix=LINUX-SECTIONS2
+
+
+define void @foo(i1 %a, i1 %b) {
+b0:
+ br i1 %a, label %b1, label %b2
+
+b1: ; preds = %b0
+ ret void
+
+b2: ; preds = %b0
+ ret void
+}
+
+;; Check that %b0 is emitted at the beginning of the function.
+; LINUX-SECTIONS1: .section .text.foo,"ax", at progbits
+; LINUX-SECTIONS1: foo:
+; LINUX-SECTIONS1: # %bb.0: # %b0
+; LINUX-SECTIONS1: jne foo.cold
+; LINUX-SECTIONS1: # %bb.2: # %b2
+; LINUX-SECTIONS1: retq
+; LINUX-SECTIONS1: .section .text.split.foo,"ax", at progbits
+; LINUX-SECTIONS1: foo.cold: # %b1
+; LINUX-SECTIONS1: retq
+
+; LINUX-SECTIONS2: .section .text.foo,"ax", at progbits
+; LINUX-SECTIONS2: foo:
+; LINUX-SECTIONS2: # %bb.0: # %b0
+; LINUX-SECTIONS2: je foo.__part.0
+; LINUX-SECTIONS2: # %bb.1: # %b1
+; LINUX-SECTIONS2: retq
+; LINUX-SECTIONS2: .section .text.foo,"ax", at progbits
+; LINUX-SECTIONS2: foo.__part.0: # %b2
+; LINUX-SECTIONS2: retq
More information about the llvm-commits
mailing list