[PATCH] D32991: [ELF] Initial migration of AVR target

[Leslie Zhai via Phabricator via llvm-commits]

xiangzhai updated this revision to Diff 98738.
xiangzhai added a comment.

Dear George,

Thanks for your reply!

> This needs testcase.

I haven't written it under test and unittests directories, but instead use bare-bones <https://coding.net/u/xiangzhai/p/lld.coding.me/git/tree/master/tests/AVR>:

  #include <math.h>
  
  #include "Bar.h"
  #include "Foo.h"
  
  void setup() {
    // put your setup code here, to run once:
    bar();
    foo();
    double s = sin(M_PI);
  }
  
  void loop() {
    // put your main code here, to run repeatedly:
  }
  
  #if __GNUC__
  int main(int argc, char *argv[]) {
    return 0;
  }
  #endif

To test the relocation R_AVR_13_PCREL (haven't been implemented yet) by avr-ld (from the AVR-GCC RPM packages available for Fedora) and NewLLD, please see the diff:

  readelf -r avr-gcc-BareMinimum.o
  
  Relocation section '.rela.text' at offset 0x1d0 contains 2 entries:
   Offset     Info    Type            Sym.Value  Sym. Name + Addend
  00000000  00000d03 R_AVR_13_PCREL    00000000   bar + 0
  00000002  00000e03 R_AVR_13_PCREL    00000000   foo + 0

with

  readelf -r clang-BareMinimum.o
  
  Relocation section '.rela.text' at offset 0xb8 contains 2 entries:
   Offset     Info    Type            Sym.Value  Sym. Name + Addend
  00000000  00000212 R_AVR_CALL        00000000   bar + 0
  00000004  00000312 R_AVR_CALL        00000000   foo + 0



> I doubt that I might drove in the wrong direction? it should not be simple as my illusion?

The relocation of R_AVR_32 in my patch might be wrong! so I am reading the source code of binutils <https://sourceware.org/git/?p=binutils.git;a=blob;f=bfd/elf32-avr.c;h=43100cd20fc0f48e26bdbd8c841c661f9c37c33f;hb=HEAD#l116> and also Dylan's fork <https://github.com/avr-llvm/lld/blob/avr-support/lib/ReaderWriter/ELF/AVR/AVRRelocationHandler.cpp#L51>. but I have to look after my little kid in the weekend :) miss you, see you next week.

Regards,
Leslie Zhai


Repository:
  rL LLVM

https://reviews.llvm.org/D32991

Files:
  ELF/InputFiles.cpp
  ELF/Target.cpp


Index: ELF/Target.cpp
===================================================================
--- ELF/Target.cpp
+++ ELF/Target.cpp
@@ -247,6 +247,15 @@
   void relocateOne(uint8_t *Loc, uint32_t Type, uint64_t Val) const override;
   bool usesOnlyLowPageBits(uint32_t Type) const override;
 };
+
+class AVRTargetInfo final : public TargetInfo {
+public:
+  AVRTargetInfo();
+  RelExpr getRelExpr(uint32_t Type, const SymbolBody &S,
+                     const uint8_t *Loc) const override;
+  int64_t getImplicitAddend(const uint8_t *Buf, uint32_t Type) const override;
+  void relocateOne(uint8_t *Loc, uint32_t Type, uint64_t Val) const override;
+};
 } // anonymous namespace
 
 TargetInfo *createTarget() {
@@ -281,6 +290,8 @@
     if (Config->EKind == ELF32LEKind)
       return make<X86_64TargetInfo<ELF32LE>>();
     return make<X86_64TargetInfo<ELF64LE>>();
+  case EM_AVR:
+    return make<AVRTargetInfo>();
   }
   fatal("unknown target machine");
 }
@@ -2411,5 +2422,34 @@
 bool MipsTargetInfo<ELFT>::usesOnlyLowPageBits(uint32_t Type) const {
   return Type == R_MIPS_LO16 || Type == R_MIPS_GOT_OFST;
 }
+
+AVRTargetInfo::AVRTargetInfo() {
+}
+
+RelExpr AVRTargetInfo::getRelExpr(uint32_t Type, const SymbolBody &S,
+                                  const uint8_t *Loc) const {
+  return R_ABS;
+}
+
+int64_t AVRTargetInfo::getImplicitAddend(const uint8_t *Buf,
+                                         uint32_t Type) const {
+  switch (Type) {
+  default:
+    return 0;
+  case R_AVR_32:
+    return SignExtend64<32>(read32le(Buf));
+  }
+}
+
+void AVRTargetInfo::relocateOne(uint8_t *Loc, uint32_t Type,
+                                uint64_t Val) const {
+  switch (Type) {
+  case R_AVR_32:
+    write32le(Loc, Val);
+    break;
+  default:
+    error(getErrorLocation(Loc) + "unrecognized reloc " + Twine(Type));
+  }
+}
 }
 }
Index: ELF/InputFiles.cpp
===================================================================
--- ELF/InputFiles.cpp
+++ ELF/InputFiles.cpp
@@ -803,6 +803,8 @@
     return T.isOSIAMCU() ? EM_IAMCU : EM_386;
   case Triple::x86_64:
     return EM_X86_64;
+  case Triple::avr:
+    return EM_AVR;
   default:
     fatal(Path + ": could not infer e_machine from bitcode target triple " +
           T.str());


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