MC: prevent early DCE of empty sections

Prevent the early elimination of sections in the object writer.  There may be
references to the section itself by other symbols, which may potentially not be
possible to resolve.  ML (Visual Studio's Macro Assembler) also seems to retain
empty sections.

The elimination of symbols and sections which are unused should really occur at
the link phase.  This will not cause any change in the resulting binary, simply
in the generated object files.

The adjustments to the other unit tests account for the fluctuating section
index caused by the appearance of sections which were previously discarded.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210373 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/MC/WinCOFFObjectWriter.cpp b/lib/MC/WinCOFFObjectWriter.cpp
index 6f9c73b9cc5ad072f815ed24ec635ea2fb4863d4..2d4b75858a5f6057332ec7ecf61eb1d33549527e 100644 (file)
--- a/lib/MC/WinCOFFObjectWriter.cpp
+++ b/lib/MC/WinCOFFObjectWriter.cpp
@@ -833,13 +833,9 @@ void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
 
   DenseMap<COFFSection *, uint16_t> SectionIndices;
   for (auto & Section : Sections) {
-    if (Layout.getSectionAddressSize(Section->MCData) > 0) {
-      size_t Number = ++Header.NumberOfSections;
-      SectionIndices[Section.get()] = Number;
-      MakeSectionReal(*Section, Number);
-    } else {
-      Section->Number = -1;
-    }
+    size_t Number = ++Header.NumberOfSections;
+    SectionIndices[Section.get()] = Number;
+    MakeSectionReal(*Section, Number);
   }
 
   Header.NumberOfSymbols = 0;

diff --git a/test/MC/COFF/alias.s b/test/MC/COFF/alias.s
index dc4f65acf74ee15152f9a716829ca19103d462be..eb5398a4ed2b1f7a695053dde6c5d67da1de89f2 100644 (file)
--- a/test/MC/COFF/alias.s
+++ b/test/MC/COFF/alias.s
@@ -1,4 +1,5 @@
-// RUN: llvm-mc -filetype=obj -triple i686-pc-win32 %s -o - | llvm-readobj -t -r | FileCheck %s
+// RUN: llvm-mc -filetype=obj -triple i686-pc-win32 %s -o - \
+// RUN:   | llvm-readobj -t -r | FileCheck %s
 
 local1:
 external_aliased_to_local = local1
@@ -36,7 +37,7 @@ weak_aliased_to_external = external2
 // CHECK-NEXT:     AuxSymbolCount: 1
 // CHECK:        }
 // CHECK:        Symbol {
-// CHECK-NEXT:     Name: local1
+// CHECK:          Name: local1
 // CHECK-NEXT:     Value: 0
 // CHECK-NEXT:     Section: .text (1)
 // CHECK-NEXT:     BaseType: Null (0x0)
@@ -89,7 +90,7 @@ weak_aliased_to_external = external2
 // CHECK-NEXT:     StorageClass: WeakExternal (0x69)
 // CHECK-NEXT:     AuxSymbolCount: 1
 // CHECK-NEXT:     AuxWeakExternal {
-// CHECK-NEXT:       Linked: external2 (9)
+// CHECK-NEXT:       Linked: external2 (13)
 // CHECK-NEXT:       Search: Library (0x2)
 // CHECK-NEXT:       Unused: (00 00 00 00 00 00 00 00 00 00)
 // CHECK-NEXT:     }

diff --git a/test/MC/COFF/basic-coff-64.s b/test/MC/COFF/basic-coff-64.s
index 89d17452d0d72937870016f006027e0b9b37326a..38a9e578a4ca889524a279b41f5a926c6078f86d 100644 (file)
--- a/test/MC/COFF/basic-coff-64.s
+++ b/test/MC/COFF/basic-coff-64.s
@@ -25,10 +25,10 @@ _main:                                  # @main
 
 // CHECK: ImageFileHeader {
 // CHECK:   Machine: IMAGE_FILE_MACHINE_AMD64
-// CHECK:   SectionCount: 2
+// CHECK:   SectionCount: 3
 // CHECK:   TimeDateStamp: {{[0-9]+}}
 // CHECK:   PointerToSymbolTable: 0x{{[0-9A-F]+}}
-// CHECK:   SymbolCount: 6
+// CHECK:   SymbolCount: 8
 // CHECK:   OptionalHeaderSize: 0
 // CHECK:   Characteristics [ (0x0)
 // CHECK:   ]

diff --git a/test/MC/COFF/basic-coff.s b/test/MC/COFF/basic-coff.s
index 9b299707a130b5dc42c6559db549cb7260a8ae9c..38bfa6d1014c6da6a51329de8c0f4d716cafd001 100644 (file)
--- a/test/MC/COFF/basic-coff.s
+++ b/test/MC/COFF/basic-coff.s
@@ -25,10 +25,10 @@ L_.str:                                 # @.str
 
 // CHECK: ImageFileHeader {
 // CHECK:   Machine: IMAGE_FILE_MACHINE_I386
-// CHECK:   SectionCount: 2
+// CHECK:   SectionCount: 3
 // CHECK:   TimeDateStamp: {{[0-9]+}}
 // CHECK:   PointerToSymbolTable: 0x{{[0-9A-F]+}}
-// CHECK:   SymbolCount: 6
+// CHECK:   SymbolCount: 8
 // CHECK:   OptionalHeaderSize: 0
 // CHECK:   Characteristics [ (0x0)
 // CHECK:   ]

diff --git a/test/MC/COFF/early-dce.s b/test/MC/COFF/early-dce.s
new file mode 100644 (file)
index 0000000..ec1a9bd
--- /dev/null
+++ b/test/MC/COFF/early-dce.s
@@ -0,0 +1,16 @@
+# RUN: llvm-mc -triple i686-windows -g -filetype obj -o - %s \
+# RUN:   | llvm-readobj -s -t | FileCheck %s
+
+       .section .rdata
+
+       .align 8
+       .global data
+data:
+       .quad 0
+
+# CHECK: Sections [
+# CHECK:  Section {
+# CHECK:    Name: .text
+# CHECK:  }
+# CHECK: ]
+

diff --git a/test/MC/COFF/linkonce.s b/test/MC/COFF/linkonce.s
index b6e81ad4b6285e6498206df70cbb30b2de6e924b..f2e350645bfce8d5219fef2f8c38d2e211aee848 100644 (file)
--- a/test/MC/COFF/linkonce.s
+++ b/test/MC/COFF/linkonce.s
@@ -91,41 +91,41 @@
 // CHECK: Symbols [
 // CHECK:   Symbol {
 // CHECK:     Name: s1
-// CHECK:     Section: s1 (1)
+// CHECK:     Section: s1 (4)
 // CHECK:     AuxSectionDef {
-// CHECK:       Number: 1
+// CHECK:       Number: 4
 // CHECK:       Selection: Any (0x2)
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: s2
-// CHECK:     Section: s2 (2)
+// CHECK:     Section: s2 (5)
 // CHECK:     AuxSectionDef {
-// CHECK:       Number: 2
+// CHECK:       Number: 5
 // CHECK:       Selection: NoDuplicates (0x1)
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: s3
-// CHECK:     Section: s3 (3)
+// CHECK:     Section: s3 (6)
 // CHECK:     AuxSectionDef {
-// CHECK:       Number: 3
+// CHECK:       Number: 6
 // CHECK:       Selection: Any (0x2)
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: s4
-// CHECK:     Section: s4 (4)
+// CHECK:     Section: s4 (7)
 // CHECK:     AuxSectionDef {
-// CHECK:       Number: 4
+// CHECK:       Number: 7
 // CHECK:       Selection: SameSize (0x3)
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: s5
-// CHECK:     Section: s5 (5)
+// CHECK:     Section: s5 (8)
 // CHECK:     AuxSectionDef {
-// CHECK:       Number: 5
+// CHECK:       Number: 8
 // CHECK:       Selection: ExactMatch (0x4)
 // CHECK:     }
 // CHECK:   }
@@ -134,17 +134,17 @@
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: s7
-// CHECK:     Section: s7 (7)
+// CHECK:     Section: s7 (10)
 // CHECK:     AuxSectionDef {
-// CHECK:       Number: 7
+// CHECK:       Number: 10
 // CHECK:       Selection: Largest (0x6)
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: s8
-// CHECK:     Section: s8 (8)
+// CHECK:     Section: s8 (11)
 // CHECK:     AuxSectionDef {
-// CHECK:       Number: 8
+// CHECK:       Number: 11
 // CHECK:       Selection: Newest (0x7)
 // CHECK:     }
 // CHECK:   }

diff --git a/test/MC/COFF/section-comdat.s b/test/MC/COFF/section-comdat.s
index a0ea7d0928d50e9c5a9b2c8c6aecd82e59d55b0a..8a7de1a1d9192a5b303bfcfea55bc1642d49a6a4 100644 (file)
--- a/test/MC/COFF/section-comdat.s
+++ b/test/MC/COFF/section-comdat.s
@@ -41,56 +41,56 @@ Symbol7:
 
 // CHECK: Sections [
 // CHECK:   Section {
-// CHECK:     Number: 1
+// CHECK:     Number: 4
 // CHECK:     Name: assocSec
 // CHECK:     Characteristics [
 // CHECK:       IMAGE_SCN_LNK_COMDAT
 // CHECK:     ]
 // CHECK:   }
 // CHECK:   Section {
-// CHECK:     Number: 2
+// CHECK:     Number: 5
 // CHECK:     Name: secName
 // CHECK:     Characteristics [
 // CHECK:       IMAGE_SCN_LNK_COMDAT
 // CHECK:     ]
 // CHECK:   }
 // CHECK:   Section {
-// CHECK:     Number: 3
+// CHECK:     Number: 6
 // CHECK:     Name: secName
 // CHECK:     Characteristics [
 // CHECK:       IMAGE_SCN_LNK_COMDAT
 // CHECK:     ]
 // CHECK:   }
 // CHECK:   Section {
-// CHECK:     Number: 4
+// CHECK:     Number: 7
 // CHECK:     Name: SecName
 // CHECK:     Characteristics [
 // CHECK:       IMAGE_SCN_LNK_COMDAT
 // CHECK:     ]
 // CHECK:   }
 // CHECK:   Section {
-// CHECK:     Number: 5
+// CHECK:     Number: 8
 // CHECK:     Name: SecName
 // CHECK:     Characteristics [
 // CHECK:       IMAGE_SCN_LNK_COMDAT
 // CHECK:     ]
 // CHECK:   }
 // CHECK:   Section {
-// CHECK:     Number: 6
+// CHECK:     Number: 9
 // CHECK:     Name: SecName
 // CHECK:     Characteristics [
 // CHECK:       IMAGE_SCN_LNK_COMDAT
 // CHECK:     ]
 // CHECK:   }
 // CHECK:   Section {
-// CHECK:     Number: 7
+// CHECK:     Number: 10
 // CHECK:     Name: SecName
 // CHECK:     Characteristics [
 // CHECK:       IMAGE_SCN_LNK_COMDAT
 // CHECK:     ]
 // CHECK:   }
 // CHECK:   Section {
-// CHECK:     Number: 8
+// CHECK:     Number: 11
 // CHECK:     Name: SecName
 // CHECK:     Characteristics [
 // CHECK:       IMAGE_SCN_LNK_COMDAT
@@ -100,7 +100,7 @@ Symbol7:
 // CHECK: Symbols [
 // CHECK:   Symbol {
 // CHECK:     Name: assocSec
-// CHECK:     Section: assocSec (1)
+// CHECK:     Section: assocSec (4)
 // CHECK:     AuxSectionDef {
 // CHECK:       Selection: Any
 // CHECK:     }
@@ -111,40 +111,40 @@ Symbol7:
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: secName
-// CHECK:     Section: secName (2)
+// CHECK:     Section: secName (5)
 // CHECK:     AuxSectionDef {
 // CHECK:       Selection: Any
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: Symbol1
-// CHECK:     Section: secName (2)
+// CHECK:     Section: secName (5)
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: secName
-// CHECK:     Section: secName (3)
+// CHECK:     Section: secName (6)
 // CHECK:     AuxSectionDef {
 // CHECK:       Selection: NoDuplicates
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: Symbol2
-// CHECK:     Section: secName (3)
+// CHECK:     Section: secName (6)
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: SecName
-// CHECK:     Section: SecName (4)
+// CHECK:     Section: SecName (7)
 // CHECK:     AuxSectionDef {
 // CHECK:       Selection: SameSize
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: Symbol3
-// CHECK:     Section: SecName (4)
+// CHECK:     Section: SecName (7)
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: SecName
-// CHECK:     Section: SecName (5)
+// CHECK:     Section: SecName (8)
 // CHECK:     AuxSymbolCount: 1
 // CHECK:     AuxSectionDef {
 // CHECK:       Selection: ExactMatch
@@ -152,40 +152,40 @@ Symbol7:
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: Symbol4
-// CHECK:     Section: SecName (5)
+// CHECK:     Section: SecName (8)
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: SecName
-// CHECK:     Section: SecName (6)
+// CHECK:     Section: SecName (9)
 // CHECK:     AuxSectionDef {
 // CHECK:       Selection: Associative
-// CHECK:       AssocSection: assocSec (1)
+// CHECK:       AssocSection: assocSec (4)
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: SecName
-// CHECK:     Section: SecName (7)
+// CHECK:     Section: SecName (10)
 // CHECK:     AuxSectionDef {
 // CHECK:       Selection: Largest
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: Symbol6
-// CHECK:     Section: SecName (7)
+// CHECK:     Section: SecName (10)
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: SecName
-// CHECK:     Section: SecName (8)
+// CHECK:     Section: SecName (11)
 // CHECK:     AuxSectionDef {
 // CHECK:       Selection: Newest (0x7)
 // CHECK:     }
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: Symbol7
-// CHECK:     Section: SecName (8)
+// CHECK:     Section: SecName (11)
 // CHECK:   }
 // CHECK:   Symbol {
 // CHECK:     Name: Symbol5
-// CHECK:     Section: SecName (6)
+// CHECK:     Section: SecName (9)
 // CHECK:   }
 // CHECK: ]

diff --git a/test/MC/COFF/section-name-encoding.s b/test/MC/COFF/section-name-encoding.s
index 74cd490bd3cb2e8a06641d51308615aa0ded99f9..7edd6d7446d9825c4176aae174554e5015943926 100644 (file)
--- a/test/MC/COFF/section-name-encoding.s
+++ b/test/MC/COFF/section-name-encoding.s
@@ -10,11 +10,11 @@
 // Raw encoding
 
 // CHECK:   Section {
-// CHECK:     Number: 1
+// CHECK:     Number: 4
 // CHECK:     Name: s (73 00 00 00 00 00 00 00)
 // CHECK:   }
 // CHECK:   Section {
-// CHECK:     Number: 2
+// CHECK:     Number: 5
 // CHECK:     Name: s1234567 (73 31 32 33 34 35 36 37)
 // CHECK:   }
 .section s;        .long 1
@@ -25,7 +25,7 @@
 
 // /4
 // CHECK:   Section {
-// CHECK:     Number: 3
+// CHECK:     Number: 6
 // CHECK:     Name: s12345678 (2F 34 00 00 00 00 00 00)
 // CHECK:   }
 .section s12345678; .long 1
@@ -57,7 +57,7 @@ pad_sections aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 //     "s12345678\0"     # of pad sections
 //
 // CHECK:   Section {
-// CHECK:     Number: 9
+// CHECK:     Number: 12
 // CHECK:     Name: seven_digit (2F 31 30 30 30 30 32 39)
 // CHECK:   }
 .section seven_digit; .long 1
@@ -82,7 +82,7 @@ pad_sections_ex aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 // "2F 2F 41 41 6D 4A 61 34" is "//AAmJa4", which decodes to "0 0 38 9 26 56".
 //
 // CHECK:   Section {
-// CHECK:     Number: 15
+// CHECK:     Number: 18
 // CHECK:     Name: double_slash (2F 2F 41 41 6D 4A 61 34)
 // CHECK:   }
 .section double_slash; .long 1

diff --git a/test/MC/COFF/seh.s b/test/MC/COFF/seh.s
index 72d42f4b2ea3a5542344b2b3f2c7e6bcb9dbf744..cd884b4fa0095b0598b9b15df67af4fb5535da60 100644 (file)
--- a/test/MC/COFF/seh.s
+++ b/test/MC/COFF/seh.s
@@ -35,13 +35,13 @@
 // CHECK-NEXT: ]
 
 // CHECK-NEXT: Relocations [
-// CHECK-NEXT:   Section (2) .xdata {
+// CHECK-NEXT:   Section (4) .xdata {
 // CHECK-NEXT:     0x14 IMAGE_REL_AMD64_ADDR32NB __C_specific_handler
 // CHECK-NEXT:     0x20 IMAGE_REL_AMD64_ADDR32NB func
 // CHECK-NEXT:     0x24 IMAGE_REL_AMD64_ADDR32NB func
 // CHECK-NEXT:     0x28 IMAGE_REL_AMD64_ADDR32NB .xdata
 // CHECK-NEXT:   }
-// CHECK-NEXT:   Section (3) .pdata {
+// CHECK-NEXT:   Section (5) .pdata {
 // CHECK-NEXT:     0x0 IMAGE_REL_AMD64_ADDR32NB func
 // CHECK-NEXT:     0x4 IMAGE_REL_AMD64_ADDR32NB func
 // CHECK-NEXT:     0x8 IMAGE_REL_AMD64_ADDR32NB .xdata

diff --git a/test/MC/COFF/symbol-fragment-offset-64.s b/test/MC/COFF/symbol-fragment-offset-64.s
index b8244709aa75c3bdf4cdbda5c4b0ae39c7a52ffb..deac88869b2028ff8871f074972ae7470a66d316 100644 (file)
--- a/test/MC/COFF/symbol-fragment-offset-64.s
+++ b/test/MC/COFF/symbol-fragment-offset-64.s
@@ -36,10 +36,10 @@ _main:                                  # @main
 
 // CHECK: {
 // CHECK:   Machine:                   IMAGE_FILE_MACHINE_AMD64
-// CHECK:   SectionCount:              2
+// CHECK:   SectionCount:              3
 // CHECK:   TimeDateStamp:             {{[0-9]+}}
 // CHECK:   PointerToSymbolTable:      0x{{[0-9A-F]+}}
-// CHECK:   SymbolCount:               7
+// CHECK:   SymbolCount:               9
 // CHECK:   OptionalHeaderSize:        0
 // CHECK:   Characteristics [ (0x0)
 // CHECK:   ]

diff --git a/test/MC/COFF/symbol-fragment-offset.s b/test/MC/COFF/symbol-fragment-offset.s
index 71b1703972ab1a4202adc22855eeae279ceff44e..b09c5af1b61e584488ebb3142ffeb2ac1879984f 100644 (file)
--- a/test/MC/COFF/symbol-fragment-offset.s
+++ b/test/MC/COFF/symbol-fragment-offset.s
@@ -36,10 +36,10 @@ L_.str2:
 
 // CHECK: {
 // CHECK:   Machine:                   IMAGE_FILE_MACHINE_I386 (0x14C)
-// CHECK:   SectionCount:              2
+// CHECK:   SectionCount:              3
 // CHECK:   TimeDateStamp:             {{[0-9]+}}
 // CHECK:   PointerToSymbolTable:      0x{{[0-9A-F]+}}
-// CHECK:   SymbolCount:               7
+// CHECK:   SymbolCount:               9
 // CHECK:   OptionalHeaderSize:        0
 // CHECK:   Characteristics [ (0x0)
 // CHECK:   ]