[lld] dd6412c - [WebAssembly][lld] Exclude COMDAT sections
Derek Schuff via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 10 17:49:39 PST 2020
Author: Derek Schuff
Date: 2020-12-10T17:47:41-08:00
New Revision: dd6412c05c1039e582a970da1aee62cdde75c892
URL: https://github.com/llvm/llvm-project/commit/dd6412c05c1039e582a970da1aee62cdde75c892
DIFF: https://github.com/llvm/llvm-project/commit/dd6412c05c1039e582a970da1aee62cdde75c892.diff
LOG: [WebAssembly][lld] Exclude COMDAT sections
Allow exclusion/discarding of custom sections with COMDAT groups.
It piggybacks on the existing COMDAT-handling code, but applies to custom sections as well.
Differential Revision: https://reviews.llvm.org/D92950
Added:
lld/test/wasm/Inputs/comdat1.s
lld/test/wasm/Inputs/comdat2.s
lld/test/wasm/comdat-sections.s
Modified:
lld/wasm/InputChunks.h
lld/wasm/InputFiles.cpp
lld/wasm/OutputSections.cpp
lld/wasm/Writer.cpp
Removed:
################################################################################
diff --git a/lld/test/wasm/Inputs/comdat1.s b/lld/test/wasm/Inputs/comdat1.s
new file mode 100644
index 000000000000..ff988ccef20f
--- /dev/null
+++ b/lld/test/wasm/Inputs/comdat1.s
@@ -0,0 +1,13 @@
+ .text
+ .section .text.foo,"G",@,foo,comdat
+ .globl foo
+ .type foo, at function
+foo:
+ .functype foo () -> ()
+ return
+ end_function
+
+ .section .debug_foo,"G",@,foo,comdat
+ .int32 1
+ .section .debug_foo,"G",@,duplicate,comdat
+ .int64 123
diff --git a/lld/test/wasm/Inputs/comdat2.s b/lld/test/wasm/Inputs/comdat2.s
new file mode 100644
index 000000000000..f498fdd105d6
--- /dev/null
+++ b/lld/test/wasm/Inputs/comdat2.s
@@ -0,0 +1,13 @@
+ .text
+ .section .text.foo,"G",@,foo,comdat
+ .globl foo
+ .type foo, at function
+foo:
+ .functype foo () -> ()
+ return
+ end_function
+
+ .section .debug_foo,"G",@,foo,comdat
+ .int32 2
+ .section .debug_foo,"G",@,duplicate,comdat
+ .int64 234
diff --git a/lld/test/wasm/comdat-sections.s b/lld/test/wasm/comdat-sections.s
new file mode 100644
index 000000000000..fc8d2ded1980
--- /dev/null
+++ b/lld/test/wasm/comdat-sections.s
@@ -0,0 +1,22 @@
+# RUN: llvm-mc -triple=wasm32 -filetype=obj %p/Inputs/comdat1.s -o %t1.o
+# RUN: llvm-mc -triple=wasm32 -filetype=obj %p/Inputs/comdat2.s -o %t2.o
+# RUN: llvm-mc -triple=wasm32 -filetype=obj %s -o %t.o
+# RUN: wasm-ld -o %t.wasm %t.o %t1.o %t2.o
+# RUN: obj2yaml %t.wasm | FileCheck %s
+
+
+ .globl _start
+ .type _start, at function
+_start:
+ .functype _start () -> ()
+ call foo
+ end_function
+
+ .functype foo () -> ()
+
+
+# Check that we got 1 copy of each of the .debug_foo sections from the 2 object
+# files, and that they came from the same object.
+# CHECK: - Type: CUSTOM
+# CHECK-NEXT: Name: .debug_foo
+# CHECK-NEXT: Payload: 010000007B00000000000000
diff --git a/lld/wasm/InputChunks.h b/lld/wasm/InputChunks.h
index ba4e2a591074..9082d1dada5f 100644
--- a/lld/wasm/InputChunks.h
+++ b/lld/wasm/InputChunks.h
@@ -221,7 +221,7 @@ class InputSection : public InputChunk {
StringRef getName() const override { return section.Name; }
StringRef getDebugName() const override { return StringRef(); }
- uint32_t getComdat() const override { return UINT32_MAX; }
+ uint32_t getComdat() const override { return section.Comdat; }
protected:
ArrayRef<uint8_t> data() const override { return section.Content; }
diff --git a/lld/wasm/InputFiles.cpp b/lld/wasm/InputFiles.cpp
index 2b3c2591058c..68a9472819e4 100644
--- a/lld/wasm/InputFiles.cpp
+++ b/lld/wasm/InputFiles.cpp
@@ -341,6 +341,12 @@ void ObjFile::parse(bool ignoreComdats) {
}
}
+ ArrayRef<StringRef> comdats = wasmObj->linkingData().Comdats;
+ for (StringRef comdat : comdats) {
+ bool isNew = ignoreComdats || symtab->addComdat(comdat);
+ keptComdats.push_back(isNew);
+ }
+
uint32_t sectionIndex = 0;
// Bool for each symbol, true if called directly. This allows us to implement
@@ -360,7 +366,9 @@ void ObjFile::parse(bool ignoreComdats) {
assert(!dataSection);
dataSection = §ion;
} else if (section.Type == WASM_SEC_CUSTOM) {
- customSections.emplace_back(make<InputSection>(section, this));
+ auto *customSec = make<InputSection>(section, this);
+ customSec->discarded = isExcludedByComdat(customSec);
+ customSections.emplace_back(customSec);
customSections.back()->setRelocations(section.Relocations);
customSectionsByIndex[sectionIndex] = customSections.back();
}
@@ -374,11 +382,6 @@ void ObjFile::parse(bool ignoreComdats) {
typeMap.resize(getWasmObj()->types().size());
typeIsUsed.resize(getWasmObj()->types().size(), false);
- ArrayRef<StringRef> comdats = wasmObj->linkingData().Comdats;
- for (StringRef comdat : comdats) {
- bool isNew = ignoreComdats || symtab->addComdat(comdat);
- keptComdats.push_back(isNew);
- }
// Populate `Segments`.
for (const WasmSegment &s : wasmObj->dataSegments()) {
@@ -487,6 +490,10 @@ Symbol *ObjFile::createDefined(const WasmSymbol &sym) {
case WASM_SYMBOL_TYPE_SECTION: {
InputSection *section = customSectionsByIndex[sym.Info.ElementIndex];
assert(sym.isBindingLocal());
+ // Need to return null if discarded here? data and func only do that when
+ // binding is not local.
+ if (section->discarded)
+ return nullptr;
return make<SectionSymbol>(flags, section, this);
}
case WASM_SYMBOL_TYPE_EVENT: {
diff --git a/lld/wasm/OutputSections.cpp b/lld/wasm/OutputSections.cpp
index 89f51ec467b1..1af448dcea74 100644
--- a/lld/wasm/OutputSections.cpp
+++ b/lld/wasm/OutputSections.cpp
@@ -239,6 +239,7 @@ void CustomSection::finalizeContents() {
os.flush();
for (InputSection *section : inputSections) {
+ assert(!section->discarded);
section->outputSec = this;
section->outputOffset = payloadSize;
payloadSize += section->getSize();
diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
index 3f255966f8db..c95b92504634 100644
--- a/lld/wasm/Writer.cpp
+++ b/lld/wasm/Writer.cpp
@@ -120,6 +120,9 @@ void Writer::calculateCustomSections() {
bool stripDebug = config->stripDebug || config->stripAll;
for (ObjFile *file : symtab->objectFiles) {
for (InputSection *section : file->customSections) {
+ // Exclude COMDAT sections that are not selected for inclusion
+ if (section->discarded)
+ continue;
StringRef name = section->getName();
// These custom sections are known the linker and synthesized rather than
// blindly copied.
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