[lld] r345088 - Factor out code to a new function. NFC.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Tue Oct 23 15:03:33 2018
New Revision: 345088

URL: http://llvm.org/viewvc/llvm-project?rev=345088&view=rev
Log:
Factor out code to a new function. NFC.

Modified:
    lld/trunk/ELF/Writer.cpp

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=345088&r1=345087&r2=345088&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Tue Oct 23 15:03:33 2018
@@ -53,6 +53,7 @@ private:
   void forEachRelSec(llvm::function_ref<void(InputSectionBase &)> Fn);
   void sortSections();
   void resolveShfLinkOrder();
+  void maybeAddThunks();
   void sortInputSections();
   void finalizeSections();
   void setReservedSymbolSections();
@@ -1461,6 +1462,46 @@ template <class ELFT> void Writer<ELFT>:
   }
 }
 
+// For most RISC ISAs, we need to generate content that depends on the address
+// of InputSections. For example some architectures such as AArch64 use small
+// displacements for jump instructions that is the linker's responsibility for
+// creating range extension thunks for. As the generation of the content may
+// also alter InputSection addresses we must converge to a fixed point.
+template <class ELFT> void Writer<ELFT>::maybeAddThunks() {
+  if (!Target->NeedsThunks && !Config->AndroidPackDynRelocs &&
+      !Config->RelrPackDynRelocs)
+    return;
+
+  ThunkCreator TC;
+  AArch64Err843419Patcher A64P;
+
+  for (;;) {
+    bool Changed = false;
+
+    Script->assignAddresses();
+
+    if (Target->NeedsThunks)
+      Changed |= TC.createThunks(OutputSections);
+
+    if (Config->FixCortexA53Errata843419) {
+      if (Changed)
+        Script->assignAddresses();
+      Changed |= A64P.createFixes();
+    }
+
+    if (In.MipsGot)
+      In.MipsGot->updateAllocSize();
+
+    Changed |= In.RelaDyn->updateAllocSize();
+
+    if (In.RelrDyn)
+      Changed |= In.RelrDyn->updateAllocSize();
+
+    if (!Changed)
+      return;
+  }
+}
+
 static void finalizeSynthetic(SyntheticSection *Sec) {
   if (Sec && !Sec->empty() && Sec->getParent())
     Sec->finalizeContents();
@@ -1693,33 +1734,17 @@ template <class ELFT> void Writer<ELFT>:
   // needs to be resolved before any other address dependent operation.
   resolveShfLinkOrder();
 
-  // Some architectures need to generate content that depends on the address
-  // of InputSections. For example some architectures use small displacements
-  // for jump instructions that is the linker's responsibility for creating
-  // range extension thunks for. As the generation of the content may also
-  // alter InputSection addresses we must converge to a fixed point.
-  if (Target->NeedsThunks || Config->AndroidPackDynRelocs ||
-      Config->RelrPackDynRelocs) {
-    ThunkCreator TC;
-    AArch64Err843419Patcher A64P;
-    bool Changed;
-    do {
-      Script->assignAddresses();
-      Changed = false;
-      if (Target->NeedsThunks)
-        Changed |= TC.createThunks(OutputSections);
-      if (Config->FixCortexA53Errata843419) {
-        if (Changed)
-          Script->assignAddresses();
-        Changed |= A64P.createFixes();
-      }
-      if (In.MipsGot)
-        In.MipsGot->updateAllocSize();
-      Changed |= In.RelaDyn->updateAllocSize();
-      if (In.RelrDyn)
-        Changed |= In.RelrDyn->updateAllocSize();
-    } while (Changed);
-  }
+  // Jump instructions in many ISAs have small displacements, and therefore they
+  // cannot jump to arbitrary addresses in memory. For example, RISC-V JAL
+  // instruction can target only +-1 MiB from PC. It is a linker's
+  // responsibility to create and insert small pieces of code between sections
+  // to extend the ranges if jump targets are out of range. Such code pieces are
+  // called "thunks".
+  //
+  // We add thunks at this stage. We couldn't do this before this point because
+  // this is the earliest point where we know sizes of sections and their
+  // layouts (that are needed to determine if jump targets are in range).
+  maybeAddThunks();
 
   // createThunks may have added local symbols to the static symbol table
   finalizeSynthetic(In.SymTab);