[llvm] [RISCV] Let -data-sections also work on sbss/sdata sections (PR #87040)
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Mon Aug 19 02:48:09 PDT 2024
https://github.com/KaiYG updated https://github.com/llvm/llvm-project/pull/87040
>From 26180ed93536588f4ce65c648ff1e9fce962f654 Mon Sep 17 00:00:00 2001
From: Kai Kai-Yi Weng <kaiweng at andestech.com>
Date: Wed, 20 Mar 2024 09:25:32 +0800
Subject: [PATCH 1/3] [RISCV] Pre-commit a test showing apply -data-sections on
sbss/sdata sections
Copied from sdata-limit-8.ll and update the CHECKs, otherwise it matches
any .sbss/.sdata regardless having a suffix or not.
---
llvm/test/CodeGen/RISCV/sdata-sections.ll | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
create mode 100644 llvm/test/CodeGen/RISCV/sdata-sections.ll
diff --git a/llvm/test/CodeGen/RISCV/sdata-sections.ll b/llvm/test/CodeGen/RISCV/sdata-sections.ll
new file mode 100644
index 00000000000000..ec9db289301940
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/sdata-sections.ll
@@ -0,0 +1,18 @@
+; RUN: llc -mtriple=riscv32 -data-sections < %s | FileCheck -check-prefix=RV32 %s
+; RUN: llc -mtriple=riscv64 -data-sections < %s | FileCheck -check-prefix=RV64 %s
+
+; FIXME: Should append an unique name to each sdata/sbss section if -data-sections,
+; otherwise gc-section cannot remove them. This also matches the behavior on gcc.
+
+ at v = dso_local global i32 0, align 4
+ at r = dso_local global i64 7, align 8
+
+; SmallDataLimit set to 8, so we expect @v will be put in sbss
+; and @r will be put in sdata.
+!llvm.module.flags = !{!0}
+!0 = !{i32 8, !"SmallDataLimit", i32 8}
+
+; RV32: .section .sbss,"aw"
+; RV32: .section .sdata,"aw"
+; RV64: .section .sbss,"aw"
+; RV64: .section .sdata,"aw"
>From eccdabb499f4340647d7432ecccb8a41826fdcda Mon Sep 17 00:00:00 2001
From: Kai Kai-Yi Weng <kaiweng at andestech.com>
Date: Wed, 20 Mar 2024 14:10:33 +0800
Subject: [PATCH 2/3] [RISCV] Let -data-sections also work on sbss/sdata
sections
Without assigning an unique .sbss/.sdata section to each symbols, a linker
may not be able to remove unused part when gc-section since all used and
unused symbols are all mixed in the same .sbss/.sdata section.
I believe this also matches the behavior of gcc.
---
.../Target/RISCV/RISCVTargetObjectFile.cpp | 34 ++++++++++++++++---
llvm/test/CodeGen/RISCV/sdata-sections.ll | 11 +++---
2 files changed, 35 insertions(+), 10 deletions(-)
diff --git a/llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp b/llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp
index e7c1a7e5d8bca1..b13df905249ab5 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp
@@ -104,10 +104,36 @@ bool RISCVELFTargetObjectFile::isGlobalInSmallSection(
MCSection *RISCVELFTargetObjectFile::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
// Handle Small Section classification here.
- if (Kind.isBSS() && isGlobalInSmallSection(GO, TM))
- return SmallBSSSection;
- if (Kind.isData() && isGlobalInSmallSection(GO, TM))
- return SmallDataSection;
+ if (isGlobalInSmallSection(GO, TM)) {
+ // Emit a unique section for sdata/sbss when -fdata-section.
+ bool EmitUniquedSection = TM.getDataSections();
+
+ if (Kind.isBSS()) {
+ if (EmitUniquedSection) {
+ StringRef Prefix(".sbss");
+ SmallString<128> Name(Prefix);
+ Name.append(".");
+ Name.append(GO->getName());
+ return getContext().getELFSection(Name.str(), ELF::SHT_NOBITS,
+ ELF::SHF_WRITE | ELF::SHF_ALLOC);
+ }
+
+ return SmallBSSSection;
+ }
+
+ if (Kind.isData()) {
+ if (EmitUniquedSection) {
+ StringRef Prefix(".sdata");
+ SmallString<128> Name(Prefix);
+ Name.append(".");
+ Name.append(GO->getName());
+ return getContext().getELFSection(Name.str(), ELF::SHT_PROGBITS,
+ ELF::SHF_WRITE | ELF::SHF_ALLOC);
+ }
+
+ return SmallDataSection;
+ }
+ }
// Otherwise, we work the same as ELF.
return TargetLoweringObjectFileELF::SelectSectionForGlobal(GO, Kind, TM);
diff --git a/llvm/test/CodeGen/RISCV/sdata-sections.ll b/llvm/test/CodeGen/RISCV/sdata-sections.ll
index ec9db289301940..175e6d744843a8 100644
--- a/llvm/test/CodeGen/RISCV/sdata-sections.ll
+++ b/llvm/test/CodeGen/RISCV/sdata-sections.ll
@@ -1,8 +1,7 @@
; RUN: llc -mtriple=riscv32 -data-sections < %s | FileCheck -check-prefix=RV32 %s
; RUN: llc -mtriple=riscv64 -data-sections < %s | FileCheck -check-prefix=RV64 %s
-; FIXME: Should append an unique name to each sdata/sbss section if -data-sections,
-; otherwise gc-section cannot remove them. This also matches the behavior on gcc.
+; Append an unique name to each sdata/sbss section when -data-section.
@v = dso_local global i32 0, align 4
@r = dso_local global i64 7, align 8
@@ -12,7 +11,7 @@
!llvm.module.flags = !{!0}
!0 = !{i32 8, !"SmallDataLimit", i32 8}
-; RV32: .section .sbss,"aw"
-; RV32: .section .sdata,"aw"
-; RV64: .section .sbss,"aw"
-; RV64: .section .sdata,"aw"
+; RV32: .section .sbss.v,"aw"
+; RV32: .section .sdata.r,"aw"
+; RV64: .section .sbss.v,"aw"
+; RV64: .section .sdata.r,"aw"
>From 816d447b6bdfbe18ec1aab30caaf31b21bfbe9e4 Mon Sep 17 00:00:00 2001
From: Kai Kai-Yi Weng <kaiweng at andestech.com>
Date: Mon, 19 Aug 2024 16:52:05 +0800
Subject: [PATCH 3/3] Polish the usage of StringRef
---
llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp b/llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp
index b13df905249ab5..a6ba1001a699c2 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetObjectFile.cpp
@@ -110,9 +110,7 @@ MCSection *RISCVELFTargetObjectFile::SelectSectionForGlobal(
if (Kind.isBSS()) {
if (EmitUniquedSection) {
- StringRef Prefix(".sbss");
- SmallString<128> Name(Prefix);
- Name.append(".");
+ SmallString<128> Name(".sbss.");
Name.append(GO->getName());
return getContext().getELFSection(Name.str(), ELF::SHT_NOBITS,
ELF::SHF_WRITE | ELF::SHF_ALLOC);
@@ -123,9 +121,7 @@ MCSection *RISCVELFTargetObjectFile::SelectSectionForGlobal(
if (Kind.isData()) {
if (EmitUniquedSection) {
- StringRef Prefix(".sdata");
- SmallString<128> Name(Prefix);
- Name.append(".");
+ SmallString<128> Name(".sdata.");
Name.append(GO->getName());
return getContext().getELFSection(Name.str(), ELF::SHT_PROGBITS,
ELF::SHF_WRITE | ELF::SHF_ALLOC);
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