sys-devel/llvm/files/cherry/5d9f419a2e01c437a35899952d3342cc96a7d9e1.patch

commit 5d9f419a2e01c437a35899952d3342cc96a7d9e1
Author: Fangrui Song <maskray@google.com>
Date:   Fri Sep 6 15:57:24 2019 +0000

    Revert "Revert r370635, it caused PR43241."
    
    This reverts commit 50d2dca22b3b05d0ee4883b0cbf93d7d15f241fc.
    
    llvm-svn: 371215

diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 8996386e99a..36cda3a1e3d 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -1901,6 +1901,26 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &args) {
   markLive<ELFT>();
   demoteSharedSymbols();
   mergeSections();
+
+  // Make copies of any input sections that need to be copied into each
+  // partition.
+  copySectionsIntoPartitions();
+
+  // Create synthesized sections such as .got and .plt. This is called before
+  // processSectionCommands() so that they can be placed by SECTIONS commands.
+  createSyntheticSections<ELFT>();
+
+  // Some input sections that are used for exception handling need to be moved
+  // into synthetic sections. Do that now so that they aren't assigned to
+  // output sections in the usual way.
+  if (!config->relocatable)
+    combineEhSections();
+
+  // Create output sections described by SECTIONS commands.
+  script->processSectionCommands();
+
+  // Two input sections with different output sections should not be folded.
+  // ICF runs after processSectionCommands() so that we know the output sections.
   if (config->icf != ICFLevel::None) {
     findKeepUniqueSections<ELFT>(args);
     doIcf<ELFT>();
diff --git a/lld/ELF/ICF.cpp b/lld/ELF/ICF.cpp
index 8b01d06b024..a780ee12448 100644
--- a/lld/ELF/ICF.cpp
+++ b/lld/ELF/ICF.cpp
@@ -74,6 +74,8 @@
 
 #include "ICF.h"
 #include "Config.h"
+#include "LinkerScript.h"
+#include "OutputSections.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "SyntheticSections.h"
@@ -304,10 +306,8 @@ bool ICF<ELFT>::equalsConstant(const InputSection *a, const InputSection *b) {
     return false;
 
   // If two sections have different output sections, we cannot merge them.
-  // FIXME: This doesn't do the right thing in the case where there is a linker
-  // script. We probably need to move output section assignment before ICF to
-  // get the correct behaviour here.
-  if (getOutputSectionName(a) != getOutputSectionName(b))
+  if (getOutputSectionName(a) != getOutputSectionName(b) ||
+      a->getParent() != b->getParent())
     return false;
 
   if (a->areRelocsRela)
@@ -499,6 +499,15 @@ template <class ELFT> void ICF<ELFT>::run() {
         isec->markDead();
     }
   });
+
+  // InputSectionDescription::sections is populated by processSectionCommands().
+  // ICF may fold some input sections assigned to output sections. Remove them.
+  for (BaseCommand *base : script->sectionCommands)
+    if (auto *sec = dyn_cast<OutputSection>(base))
+      for (BaseCommand *sub_base : sec->sectionCommands)
+        if (auto *isd = dyn_cast<InputSectionDescription>(sub_base))
+          llvm::erase_if(isd->sections,
+                         [](InputSection *isec) { return !isec->isLive(); });
 }
 
 // ICF entry point function.
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 2fc9b0b091d..dbf705dc7f0 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -48,24 +48,22 @@ using namespace lld::elf;
 
 LinkerScript *elf::script;
 
-static uint64_t getOutputSectionVA(SectionBase *inputSec, StringRef loc) {
-  if (OutputSection *os = inputSec->getOutputSection())
-    return os->addr;
-  error(loc + ": unable to evaluate expression: input section " +
-        inputSec->name + " has no output section assigned");
-  return 0;
+static uint64_t getOutputSectionVA(SectionBase *sec) {
+  OutputSection *os = sec->getOutputSection();
+  assert(os && "input section has no output section assigned");
+  return os ? os->addr : 0;
 }
 
 uint64_t ExprValue::getValue() const {
   if (sec)
-    return alignTo(sec->getOffset(val) + getOutputSectionVA(sec, loc),
+    return alignTo(sec->getOffset(val) + getOutputSectionVA(sec),
                    alignment);
   return alignTo(val, alignment);
 }
 
 uint64_t ExprValue::getSecAddr() const {
   if (sec)
-    return sec->getOffset(0) + getOutputSectionVA(sec, loc);
+    return sec->getOffset(0) + getOutputSectionVA(sec);
   return 0;
 }
 
@@ -73,7 +71,7 @@ uint64_t ExprValue::getSectionOffset() const {
   // If the alignment is trivial, we don't have to compute the full
   // value to know the offset. This allows this function to succeed in
   // cases where the output section is not yet known.
-  if (alignment == 1 && (!sec || !sec->getOutputSection()))
+  if (alignment == 1 && !sec)
     return val;
   return getValue() - getSecAddr();
 }
@@ -157,8 +155,8 @@ static bool shouldDefineSym(SymbolAssignment *cmd) {
   return false;
 }
 
-// This function is called from processSectionCommands,
-// while we are fixing the output section layout.
+// Called by processSymbolAssignments() to assign definitions to
+// linker-script-defined symbols.
 void LinkerScript::addSymbol(SymbolAssignment *cmd) {
   if (!shouldDefineSym(cmd))
     return;
@@ -478,36 +476,10 @@ LinkerScript::createInputSectionList(OutputSection &outCmd) {
   return ret;
 }
 
+// Create output sections described by SECTIONS commands.
 void LinkerScript::processSectionCommands() {
-  // A symbol can be assigned before any section is mentioned in the linker
-  // script. In an DSO, the symbol values are addresses, so the only important
-  // section values are:
-  // * SHN_UNDEF
-  // * SHN_ABS
-  // * Any value meaning a regular section.
-  // To handle that, create a dummy aether section that fills the void before
-  // the linker scripts switches to another section. It has an index of one
-  // which will map to whatever the first actual section is.
-  aether = make<OutputSection>("", 0, SHF_ALLOC);
-  aether->sectionIndex = 1;
-
-  // Ctx captures the local AddressState and makes it accessible deliberately.
-  // This is needed as there are some cases where we cannot just
-  // thread the current state through to a lambda function created by the
-  // script parser.
-  auto deleter = std::make_unique<AddressState>();
-  ctx = deleter.get();
-  ctx->outSec = aether;
-
   size_t i = 0;
-  // Add input sections to output sections.
   for (BaseCommand *base : sectionCommands) {
-    // Handle symbol assignments outside of any output section.
-    if (auto *cmd = dyn_cast<SymbolAssignment>(base)) {
-      addSymbol(cmd);
-      continue;
-    }
-
     if (auto *sec = dyn_cast<OutputSection>(base)) {
       std::vector<InputSection *> v = createInputSectionList(*sec);
 
@@ -533,12 +505,6 @@ void LinkerScript::processSectionCommands() {
         continue;
       }
 
-      // A directive may contain symbol definitions like this:
-      // ".foo : { ...; bar = .; }". Handle them.
-      for (BaseCommand *base : sec->sectionCommands)
-        if (auto *outCmd = dyn_cast<SymbolAssignment>(base))
-          addSymbol(outCmd);
-
       // Handle subalign (e.g. ".foo : SUBALIGN(32) { ... }"). If subalign
       // is given, input sections are aligned to that value, whether the
       // given value is larger or smaller than the original section alignment.
@@ -548,7 +514,7 @@ void LinkerScript::processSectionCommands() {
           s->alignment = subalign;
       }
 
-      // Add input sections to an output section.
+      // Some input sections may be removed from the list after ICF.
       for (InputSection *s : v)
         sec->addSection(s);
 
@@ -559,6 +525,32 @@ void LinkerScript::processSectionCommands() {
         sec->flags &= ~(uint64_t)SHF_ALLOC;
     }
   }
+}
+
+void LinkerScript::processSymbolAssignments() {
+  // Dot outside an output section still represents a relative address, whose
+  // sh_shndx should not be SHN_UNDEF or SHN_ABS. Create a dummy aether section
+  // that fills the void outside a section. It has an index of one, which is
+  // indistinguishable from any other regular section index.
+  aether = make<OutputSection>("", 0, SHF_ALLOC);
+  aether->sectionIndex = 1;
+
+  // ctx captures the local AddressState and makes it accessible deliberately.
+  // This is needed as there are some cases where we cannot just thread the
+  // current state through to a lambda function created by the script parser.
+  AddressState state;
+  ctx = &state;
+  ctx->outSec = aether;
+
+  for (BaseCommand *base : sectionCommands) {
+    if (auto *cmd = dyn_cast<SymbolAssignment>(base))
+      addSymbol(cmd);
+    else
+      for (BaseCommand *sub_base : cast<OutputSection>(base)->sectionCommands)
+        if (auto *cmd = dyn_cast<SymbolAssignment>(sub_base))
+          addSymbol(cmd);
+  }
+
   ctx = nullptr;
 }
 
diff --git a/lld/ELF/LinkerScript.h b/lld/ELF/LinkerScript.h
index 5607b313031..4ac9e2a3909 100644
--- a/lld/ELF/LinkerScript.h
+++ b/lld/ELF/LinkerScript.h
@@ -274,6 +274,7 @@ public:
   const Defined *assignAddresses();
   void allocateHeaders(std::vector<PhdrEntry *> &phdrs);
   void processSectionCommands();
+  void processSymbolAssignments();
   void declareSymbols();
 
   // Used to handle INSERT AFTER statements.
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index b9f6aee701d..5c6fcc8532c 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -152,7 +152,7 @@ static void removeEmptyPTLoad(std::vector<PhdrEntry *> &phdrs) {
   });
 }
 
-static void copySectionsIntoPartitions() {
+void elf::copySectionsIntoPartitions() {
   std::vector<InputSectionBase *> newSections;
   for (unsigned part = 2; part != partitions.size() + 1; ++part) {
     for (InputSectionBase *s : inputSections) {
@@ -308,8 +308,7 @@ static OutputSection *findSection(StringRef name, unsigned partition = 1) {
   return nullptr;
 }
 
-// Initialize Out members.
-template <class ELFT> static void createSyntheticSections() {
+template <class ELFT> void elf::createSyntheticSections() {
   // Initialize all pointers with NULL. This is needed because
   // you can call lld::elf::main more than once as a library.
   memset(&Out::first, 0, sizeof(Out));
@@ -535,24 +534,6 @@ template <class ELFT> static void createSyntheticSections() {
 
 // The main function of the writer.
 template <class ELFT> void Writer<ELFT>::run() {
-  // Make copies of any input sections that need to be copied into each
-  // partition.
-  copySectionsIntoPartitions();
-
-  // Create linker-synthesized sections such as .got or .plt.
-  // Such sections are of type input section.
-  createSyntheticSections<ELFT>();
-
-  // Some input sections that are used for exception handling need to be moved
-  // into synthetic sections. Do that now so that they aren't assigned to
-  // output sections in the usual way.
-  if (!config->relocatable)
-    combineEhSections();
-
-  // We want to process linker script commands. When SECTIONS command
-  // is given we let it create sections.
-  script->processSectionCommands();
-
   // Linker scripts controls how input sections are assigned to output sections.
   // Input sections that were not handled by scripts are called "orphans", and
   // they are assigned to output sections by the default rule. Process that.
@@ -1737,8 +1718,14 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
   symtab->forEachSymbol(
       [](Symbol *s) { s->isPreemptible = computeIsPreemptible(*s); });
 
+  // Change values of linker-script-defined symbols from placeholders (assigned
+  // by declareSymbols) to actual definitions.
+  script->processSymbolAssignments();
+
   // Scan relocations. This must be done after every symbol is declared so that
-  // we can correctly decide if a dynamic relocation is needed.
+  // we can correctly decide if a dynamic relocation is needed. This is called
+  // after processSymbolAssignments() because it needs to know whether a
+  // linker-script-defined symbol is absolute.
   if (!config->relocatable) {
     forEachRelSec(scanRelocations<ELFT>);
     reportUndefinedSymbols<ELFT>();
@@ -2731,6 +2718,11 @@ template <class ELFT> void Writer<ELFT>::writeBuildId() {
     part.buildId->writeBuildId(buildId);
 }
 
+template void elf::createSyntheticSections<ELF32LE>();
+template void elf::createSyntheticSections<ELF32BE>();
+template void elf::createSyntheticSections<ELF64LE>();
+template void elf::createSyntheticSections<ELF64BE>();
+
 template void elf::writeResult<ELF32LE>();
 template void elf::writeResult<ELF32BE>();
 template void elf::writeResult<ELF64LE>();
diff --git a/lld/ELF/Writer.h b/lld/ELF/Writer.h
index 18c0ccfa183..3698544d977 100644
--- a/lld/ELF/Writer.h
+++ b/lld/ELF/Writer.h
@@ -20,6 +20,8 @@ namespace elf {
 class InputFile;
 class OutputSection;
 class InputSectionBase;
+void copySectionsIntoPartitions();
+template <class ELFT> void createSyntheticSections();
 void combineEhSections();
 template <class ELFT> void writeResult();
 
diff --git a/lld/test/ELF/linkerscript/early-assign-symbol.s b/lld/test/ELF/linkerscript/early-assign-symbol.s
index 5f611786366..7271204221a 100644
--- a/lld/test/ELF/linkerscript/early-assign-symbol.s
+++ b/lld/test/ELF/linkerscript/early-assign-symbol.s
@@ -1,12 +1,15 @@
 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 
-# RUN: echo "SECTIONS { aaa = foo | 1; .text  : { *(.text*) } }" > %t3.script
-# RUN: not ld.lld -o %t --script %t3.script %t.o 2>&1 | FileCheck %s
+## The definitions of symbol assignments may reference other symbols.
+## Test we can handle them.
 
-# CHECK: error: {{.*}}.script:1: unable to evaluate expression: input section .text has no output section assigned
+# RUN: echo "SECTIONS { aaa = foo | 1; .text  : { *(.text*) } }" > %t3.script
+# RUN: ld.lld -o %t --script %t3.script %t.o
+# RUN: llvm-objdump -t %t | FileCheck --check-prefix=VAL1 %s
 
-# Simple cases that we can handle.
+# VAL1: 0000000000000000 .text 00000000 foo
+# VAL1: 0000000000000001 .text 00000000 aaa
 
 # RUN: echo "SECTIONS { aaa = ABSOLUTE(foo - 1) + 1; .text  : { *(.text*) } }" > %t.script
 # RUN: ld.lld -o %t --script %t.script %t.o
diff --git a/lld/test/ELF/linkerscript/icf-output-sections.s b/lld/test/ELF/linkerscript/icf-output-sections.s
new file mode 100644
index 00000000000..f23d7fff06b
--- /dev/null
+++ b/lld/test/ELF/linkerscript/icf-output-sections.s
@@ -0,0 +1,46 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
+# RUN: echo 'SECTIONS { .text : { *(.text*) } }' > %t1.script
+
+## Sections within the same output section can be freely folded.
+# RUN: ld.lld %t.o --script %t1.script --icf=all --print-icf-sections -o %t | FileCheck --check-prefix=ICF1 %s
+# RUN: llvm-readelf -S %t | FileCheck --check-prefix=SEC1 %s --implicit-check-not=.text
+
+# ICF1:      selected section {{.*}}.o:(.text.foo0)
+# ICF1-NEXT:   removing identical section {{.*}}.o:(.text.foo1)
+# ICF1-NEXT:   removing identical section {{.*}}.o:(.text.bar0)
+# ICF1-NEXT:   removing identical section {{.*}}.o:(.text.bar1)
+
+# SEC1: .text   PROGBITS 0000000000000000 001000 000001
+
+## Sections with different output sections cannot be folded. Without the
+## linker script, .text.foo* and .text.bar* go to the same output section
+## .text and they will be folded.
+# RUN: echo 'SECTIONS { .text.foo : {*(.text.foo*)} .text.bar : {*(.text.bar*)} }' > %t2.script
+# RUN: ld.lld %t.o --script %t2.script --icf=all --print-icf-sections -o %t | FileCheck --check-prefix=ICF2 %s
+# RUN: llvm-readelf -S %t | FileCheck --check-prefix=SEC2 %s
+
+# ICF2:      selected section {{.*}}.o:(.text.foo0)
+# ICF2-NEXT:   removing identical section {{.*}}.o:(.text.foo1)
+# ICF2-NEXT: selected section {{.*}}.o:(.text.bar0)
+# ICF2-NEXT:   removing identical section {{.*}}.o:(.text.bar1)
+
+# SEC2:      .text.foo   PROGBITS 0000000000000000 001000 000001
+# SEC2-NEXT: .text.bar   PROGBITS 0000000000000001 001001 000001
+
+## .text.bar* are orphans that get assigned to .text.
+# RUN: echo 'SECTIONS { .text.foo : {*(.text.foo*)} }' > %t3.script
+# RUN: ld.lld %t.o --script %t3.script --icf=all --print-icf-sections -o %t | FileCheck --check-prefix=ICF2 %s
+# RUN: llvm-readelf -S %t | FileCheck --check-prefix=SEC3 %s
+
+# SEC3:      .text.foo   PROGBITS 0000000000000000 001000 000001
+# SEC3-NEXT: .text       PROGBITS 0000000000000004 001004 000001
+
+.section .text.foo0,"ax"
+ret
+.section .text.foo1,"ax"
+ret
+.section .text.bar0,"ax"
+ret
+.section .text.bar1,"ax"
+ret
diff --git a/lld/test/ELF/linkerscript/subalign.s b/lld/test/ELF/linkerscript/subalign.s
index 99cb3f19a99..8d8420c0f77 100644
--- a/lld/test/ELF/linkerscript/subalign.s
+++ b/lld/test/ELF/linkerscript/subalign.s
@@ -23,11 +23,11 @@
 # SUBALIGN:   03000000 00000000 04000000 00000000
 
 ## Test we do not assert or crash when dot(.) is used inside SUBALIGN.
-## ld.bfd does not allow to use dot in such expressions, our behavior is
-## different for simplicity of implementation. Value of dot is undefined.
+## Value of dot is undefined. Some versions of ld.bfd do not allow to use dot
+## in such expressions.
 # RUN: echo "SECTIONS { . = 0x32; .aaa : SUBALIGN(.) { *(.aaa*) } }" > %t3.script
-# RUN: ld.lld %t1.o --script %t3.script -o %t3
-# RUN: llvm-objdump -s %t3 > /dev/null
+# RUN: not ld.lld %t1.o --script %t3.script -o /dev/null 2>&1 | FileCheck --check-prefix=ERR1 %s
+# ERR1: {{.*}}.script:1: unable to get location counter value
 
 ## Test we are able to link with zero alignment, this is consistent with bfd 2.26.1.
 # RUN: echo "SECTIONS { .aaa : SUBALIGN(0) { *(.aaa*) } }" > %t4.script
@@ -36,8 +36,8 @@
 
 ## Test we fail gracefuly when alignment value is not a power of 2.
 # RUN: echo "SECTIONS { .aaa : SUBALIGN(3) { *(.aaa*) } }" > %t5.script
-# RUN: not ld.lld %t1.o --script %t5.script -o /dev/null 2>&1 | FileCheck -check-prefix=ERR %s
-# ERR: {{.*}}.script:1: alignment must be power of 2
+# RUN: not ld.lld %t1.o --script %t5.script -o /dev/null 2>&1 | FileCheck --check-prefix=ERR2 %s
+# ERR2: {{.*}}.script:1: alignment must be power of 2
 
 .global _start
 _start: