[ELF] Allow getErrPlace() to work before Out::bufferStart is set

Summary:
So far it seems like the only test affected by this change is the one I
recently added for R_MIPS_JALR relocations since the other test cases that
use this function early (unknown-relocation-*) do not have a valid input
section for the relocation offset.

Reviewers: ruiu, grimar, MaskRay, espindola

Reviewed By: ruiu, MaskRay

Subscribers: emaste, sdardis, jrtc27, atanasyan, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70659

Author: arichardson

lld/ELF/Target.cpp

@@ -91,15 +91,15 @@ TargetInfo *getTarget() {
 }
 
 template <class ELFT> static ErrorPlace getErrPlace(const uint8_t *loc) {
-  if (!Out::bufferStart)
-    return {};
-
   for (InputSectionBase *d : inputSections) {
     auto *isec = cast<InputSection>(d);
     if (!isec->getParent())
       continue;
 
-    uint8_t *isecLoc = Out::bufferStart + isec->getParent()->offset + isec->outSecOff;
+    const uint8_t *isecLoc =
+        Out::bufferStart
+            ? (Out::bufferStart + isec->getParent()->offset + isec->outSecOff)
+            : isec->data().data();
     if (isecLoc <= loc && loc < isecLoc + isec->getSize())
       return {isec, isec->template getLocation<ELFT>(loc - isecLoc) + ": "};
   }

lld/test/ELF/mips-jalr-non-functions.s

@@ -15,13 +15,13 @@ test:
 .Ltmp1:
   jr  $t9
   nop
-# WARNING-MESSAGE: warning: found R_MIPS_JALR relocation against non-function symbol tls_obj. This is invalid and most likely a compiler bug.
+# WARNING-MESSAGE: warning: {{.+}}.tmp.o:(.text+0x0): found R_MIPS_JALR relocation against non-function symbol tls_obj. This is invalid and most likely a compiler bug.
 
   .reloc .Ltmp2, R_MIPS_JALR, reg_obj
 .Ltmp2:
   jr  $t9
   nop
-# WARNING-MESSAGE: warning: found R_MIPS_JALR relocation against non-function symbol reg_obj. This is invalid and most likely a compiler bug.
+# WARNING-MESSAGE: warning: {{.+}}.tmp.o:(.text+0x8): found R_MIPS_JALR relocation against non-function symbol reg_obj. This is invalid and most likely a compiler bug.
 
   .reloc .Ltmp3, R_MIPS_JALR, untyped
 .Ltmp3: