[llvm-objcopy] Support -X|--discard-locals.

Summary:
This adds support for the --discard-locals flag, which acts similarly to --discard-all, except it only applies to compiler-generated symbols (i.e. symbols starting with `.L` in ELF).

I am not sure about COFF local symbols: those appear to also use `.L` in most cases, but also use just `L` in other cases, so for now I am just leaving it unimplemented there.

Fixes PR36160

Reviewers: jhenderson, alexshap, jakehehrlich, mstorsjo, espindola

Reviewed By: jhenderson

Subscribers: llvm-commits, emaste, arichardson

Differential Revision: https://reviews.llvm.org/D57248

llvm-svn: 352626

3 files changed, 255 insertions, 0 deletions

diff --git a/llvm/test/tools/llvm-objcopy/ELF/discard-locals-rel.test b/llvm/test/tools/llvm-objcopy/ELF/discard-locals-rel.test
new file mode 100644
index 00000000000..05e1acf6b1d
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/ELF/discard-locals-rel.test
@@ -0,0 +1,27 @@
+# RUN: yaml2obj %s > %t
+# RUN: not llvm-objcopy --discard-locals %t %t2 2>&1 | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Link:            .symtab
+    Info:            .text
+    Relocations:
+      - Offset: 0x1000
+        Symbol: .L.rel
+        Type:   R_X86_64_PC32
+Symbols:
+  Local:
+    - Name:     .L.rel
+      Type:     STT_FUNC
+      Section:  .text
+
+# CHECK: not stripping symbol '.L.rel' because it is named in a relocation.
diff --git a/llvm/test/tools/llvm-objcopy/ELF/discard-locals.test b/llvm/test/tools/llvm-objcopy/ELF/discard-locals.test
new file mode 100644
index 00000000000..be489a2f0de
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/ELF/discard-locals.test
@@ -0,0 +1,121 @@
+# RUN: yaml2obj %s > %t
+# RUN: cp %t %t1
+# RUN: llvm-objcopy --discard-locals %t %t2
+# Verify that llvm-objcopy has not modified the input.
+# RUN: cmp %t %t1
+# RUN: llvm-readobj --symbols %t2 | FileCheck %s
+
+# RUN: llvm-objcopy -X %t %t3
+# Verify that llvm-objcopy has not modified the input.
+# RUN: cmp %t %t1
+# RUN: cmp %t2 %t3
+
+# Verify that llvm-strip modifies the symbol table the same way.
+
+# RUN: cp %t %t4
+# RUN: llvm-strip --discard-locals %t4
+# RUN: cmp %t2 %t4
+
+# RUN: cp %t %t5
+# RUN: llvm-strip -X %t5
+# RUN: cmp %t2 %t5
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+  - Name:            .LLVM.Custom.Section
+    Type:            SHT_PROGBITS
+Symbols:
+  Local:
+    - Name:     Local
+      Type:     STT_FUNC
+      Section:  .text
+    - Name:     .L.LocalSection
+      Type:     STT_SECTION
+      Section:  .text
+    - Type:     STT_SECTION
+      Section:  .LLVM.Custom.Section
+    - Name:     .L.LocalFile
+      Type:     STT_FILE
+    - Name:     .L.str
+      Type:     STT_OBJECT
+      Section:  .text
+    - Name:     .L.undefined
+    - Name:     .L.abs
+      Index:    SHN_ABS
+  Global:
+    - Name:     .L.Global
+      Type:     STT_FUNC
+      Section:  .text
+
+# CHECK:      Symbols [
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name:
+# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Local
+# CHECK-NEXT:     Type: None
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: Undefined
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: Local
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Local
+# CHECK-NEXT:     Type: Function
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: .text
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: .L.LocalSection
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Local
+# CHECK-NEXT:     Type: Section
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: .text
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name:
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Local
+# CHECK-NEXT:     Type: Section
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: .LLVM.Custom.Section
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: .L.LocalFile
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Local
+# CHECK-NEXT:     Type: File
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: Undefined
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: .L.undefined
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Local
+# CHECK-NEXT:     Type: None
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: Undefined
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: .L.Global
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Global
+# CHECK-NEXT:     Type: Function
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: .text
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
diff --git a/llvm/test/tools/llvm-objcopy/ELF/discard-mix-local-and-all.test b/llvm/test/tools/llvm-objcopy/ELF/discard-mix-local-and-all.test
new file mode 100644
index 00000000000..f9e0613eecf
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/ELF/discard-mix-local-and-all.test
@@ -0,0 +1,107 @@
+# RUN: yaml2obj %s > %t
+# Establish baseline objects for further checks. --discard-locals only discards
+# compiler-generated local symbols (starting with .L), --discard-all discards
+# all regular local symbols.
+# RUN: llvm-objcopy %t %t-discard-none
+# RUN: llvm-readobj --symbols %t-discard-none | FileCheck %s --check-prefixes=CHECK,LOCAL,COMPILER-LOCAL
+# RUN: llvm-objcopy --discard-all %t %t-discard-all
+# RUN: llvm-readobj --symbols %t-discard-all | FileCheck %s
+# RUN: llvm-objcopy --discard-locals %t %t-discard-locals
+# RUN: llvm-readobj --symbols %t-discard-locals | FileCheck %s --check-prefixes=CHECK,LOCAL
+
+# When mixing --discard-all and --discard-locals, the last one wins.
+# RUN: llvm-objcopy --discard-all --discard-locals %t %t.1.o
+# RUN: cmp %t.1.o %t-discard-locals
+# RUN: llvm-objcopy --discard-locals --discard-all %t %t.2.o
+# RUN: cmp %t.2.o %t-discard-all
+# RUN: llvm-objcopy -x -X %t %t.3.o
+# RUN: cmp %t.3.o %t-discard-locals
+# RUN: llvm-objcopy -X -x %t %t.4.o
+# RUN: cmp %t.4.o %t-discard-all
+# RUN: llvm-objcopy -x -X -x -X %t %t.5.o
+# RUN: cmp %t.5.o %t-discard-locals
+# RUN: llvm-objcopy -X -x -X -x %t %t.6.o
+# RUN: cmp %t.6.o %t-discard-all
+# RUN: llvm-objcopy -X -x -X -x --discard-locals %t %t.7.o
+# RUN: cmp %t.7.o %t-discard-locals
+# RUN: llvm-objcopy -X -x -X -x --discard-all %t %t.8.o
+# RUN: cmp %t.8.o %t-discard-all
+
+# llvm-strip works in the same way.
+# RUN: llvm-strip --discard-all --discard-locals %t -o %t.9.o
+# RUN: cmp %t.9.o %t-discard-locals
+# RUN: llvm-strip --discard-locals --discard-all %t -o %t.10.o
+# RUN: cmp %t.10.o %t-discard-all
+# RUN: llvm-strip -x -X %t -o %t.11.o
+# RUN: cmp %t.11.o %t-discard-locals
+# RUN: llvm-strip -X -x %t -o %t.12.o
+# RUN: cmp %t.12.o %t-discard-all
+# RUN: llvm-strip -x -X -x -X %t -o %t.13.o
+# RUN: cmp %t.13.o %t-discard-locals
+# RUN: llvm-strip -X -x -X -x %t -o %t.14.o
+# RUN: cmp %t.14.o %t-discard-all
+# RUN: llvm-strip -X -x -X -x --discard-locals %t -o %t.15.o
+# RUN: cmp %t.15.o %t-discard-locals
+# RUN: llvm-strip -X -x -X -x --discard-all %t -o %t.16.o
+# RUN: cmp %t.16.o %t-discard-all
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+Symbols:
+  Local:
+    - Name:     Local
+      Type:     STT_FUNC
+      Section:  .text
+    - Name:     .L.str
+      Type:     STT_OBJECT
+      Section:  .text
+  Global:
+    - Name:     Global
+      Type:     STT_FUNC
+      Section:  .text
+
+# CHECK:               Symbols [
+# CHECK-NEXT:            Symbol {
+# CHECK-NEXT:              Name:
+# CHECK-NEXT:              Value: 0x0
+# CHECK-NEXT:              Size: 0
+# CHECK-NEXT:              Binding: Local
+# CHECK-NEXT:              Type: None
+# CHECK-NEXT:              Other: 0
+# CHECK-NEXT:              Section: Undefined
+# CHECK-NEXT:            }
+# LOCAL-NEXT:            Symbol {
+# LOCAL-NEXT:              Name: Local
+# LOCAL-NEXT:              Value:
+# LOCAL-NEXT:              Size:
+# LOCAL-NEXT:              Binding: Local
+# LOCAL-NEXT:              Type: Function
+# LOCAL-NEXT:              Other:
+# LOCAL-NEXT:              Section: .text
+# LOCAL-NEXT:            }
+# COMPILER-LOCAL-NEXT:   Symbol {
+# COMPILER-LOCAL-NEXT:     Name: .L.str
+# COMPILER-LOCAL-NEXT:     Value:
+# COMPILER-LOCAL-NEXT:     Size:
+# COMPILER-LOCAL-NEXT:     Binding: Local
+# COMPILER-LOCAL-NEXT:     Type: Object
+# COMPILER-LOCAL-NEXT:     Other:
+# COMPILER-LOCAL-NEXT:     Section: .text
+# COMPILER-LOCAL-NEXT:   }
+# CHECK-NEXT:            Symbol {
+# CHECK-NEXT:              Name: Global
+# CHECK-NEXT:              Value:
+# CHECK-NEXT:              Size:
+# CHECK-NEXT:              Binding: Global
+# CHECK-NEXT:              Type: Function
+# CHECK-NEXT:              Other:
+# CHECK-NEXT:              Section: .text
+# CHECK-NEXT:            }
+# CHECK-NEXT:          ]