[lld] [LLD][COFF] Sort base relocations (PR #121699)

[Jacek Caban via llvm-commits]

https://github.com/cjacek created https://github.com/llvm/llvm-project/pull/121699

This change ensures that base relocations are sorted in the output, aligning with MSVC linker behavior. While input files typically provide sorted relocations, this update guarantees correct sorting even if the input relocations are unordered.

>From d364deaab66219a93a65a568c5526bb9880f61eb Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek at codeweavers.com>
Date: Fri, 3 Jan 2025 19:58:04 +0100
Subject: [PATCH] [LLD][COFF] Sort base relocations

This change ensures that base relocations are sorted in the output, aligning with MSVC linker behavior.
While input files typically provide sorted relocations, this update guarantees correct sorting even if
the input relocations are unordered.
---
 lld/COFF/Writer.cpp             |  2 +
 lld/test/COFF/baserel-sort.yaml | 77 +++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)
 create mode 100644 lld/test/COFF/baserel-sort.yaml

diff --git a/lld/COFF/Writer.cpp b/lld/COFF/Writer.cpp
index a5b2b6238db1a9..138112f109fd43 100644
--- a/lld/COFF/Writer.cpp
+++ b/lld/COFF/Writer.cpp
@@ -2560,6 +2560,8 @@ void Writer::addBaserelBlocks(std::vector<Baserel> &v) {
   const uint32_t mask = ~uint32_t(pageSize - 1);
   uint32_t page = v[0].rva & mask;
   size_t i = 0, j = 1;
+  llvm::sort(v,
+             [](const Baserel &x, const Baserel &y) { return x.rva < y.rva; });
   for (size_t e = v.size(); j < e; ++j) {
     uint32_t p = v[j].rva & mask;
     if (p == page)
diff --git a/lld/test/COFF/baserel-sort.yaml b/lld/test/COFF/baserel-sort.yaml
new file mode 100644
index 00000000000000..d5affe11b2189b
--- /dev/null
+++ b/lld/test/COFF/baserel-sort.yaml
@@ -0,0 +1,77 @@
+# Verify that lld-link outputs sorted base relocations, even if the input file has unsorted entries.
+
+# RUN: yaml2obj %s -o %t.obj
+# RUN: lld-link -dll -entry:sym -machine:amd64 -out:%t.dll %t.obj
+# RUN: llvm-readobj --coff-basereloc %t.dll | FileCheck %s
+
+# CHECK:      BaseReloc [
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Type: DIR64
+# CHECK-NEXT:     Address: 0x2000
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Type: DIR64
+# CHECK-NEXT:     Address: 0x2008
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Type: DIR64
+# CHECK-NEXT:     Address: 0x2010
+# CHECK-NEXT:   }
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: [  ]
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     C3
+    SizeOfRawData:   1
+  - Name:            .test
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+    Alignment:       1
+    SectionData:     '000000000000000000000000000000000000000000000000'
+    SizeOfRawData:   24
+    Relocations:
+      - VirtualAddress:  16
+        SymbolName:      sym
+        Type:            IMAGE_REL_AMD64_ADDR64
+      - VirtualAddress:  0
+        SymbolName:      sym
+        Type:            IMAGE_REL_AMD64_ADDR64
+      - VirtualAddress:  8
+        SymbolName:      sym
+        Type:            IMAGE_REL_AMD64_ADDR64
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          1
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        40735498
+      Number:          1
+  - Name:            .test
+    Value:           0
+    SectionNumber:   2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          24
+      NumberOfRelocations: 3
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          2
+  - Name:            sym
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...