Fix a bug in R_X86_64_PC{8,16} relocation handling.

R_X86_64_PC{8,16} relocations are sign-extended, so when we check
for relocation overflow, we had to use checkInt instead of checkUInt.
I confirmed that GNU linkers create the same output for the test case.

llvm-svn: 353437

lld/ELF/Arch/X86_64.cpp

@@ -324,15 +324,21 @@ template <class ELFT>
 void X86_64<ELFT>::relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const {
   switch (Type) {
   case R_X86_64_8:
-  case R_X86_64_PC8:
     checkUInt(Loc, Val, 8, Type);
     *Loc = Val;
     break;
+  case R_X86_64_PC8:
+    checkInt(Loc, Val, 8, Type);
+    *Loc = Val;
+    break;
   case R_X86_64_16:
-  case R_X86_64_PC16:
     checkUInt(Loc, Val, 16, Type);
     write16le(Loc, Val);
     break;
+  case R_X86_64_PC16:
+    checkInt(Loc, Val, 16, Type);
+    write16le(Loc, Val);
+    break;
   case R_X86_64_32:
     checkUInt(Loc, Val, 32, Type);
     write32le(Loc, Val);

lld/test/ELF/Inputs/x86-64-pcrel.s

@@ -0,0 +1,8 @@
+.globl foo
+foo:
+
+.word _start - foo
+.fill 14,1,0xcc
+
+.byte _start - foo
+.fill 15,1,0xcc

lld/test/ELF/x86-64-pcrel.s

@@ -3,13 +3,15 @@
 // This is a test for R_X86_64_PC8 and R_X86_64_PC16.
 
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t1.o
-// RUN: echo '.globl foo; foo:' | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %t2.o
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/x86-64-pcrel.s -o %t2.o
 // RUN: ld.lld -o %t.exe %t1.o %t2.o
 // RUN: llvm-objdump -s %t.exe | FileCheck %s
 
-// CHECK: Contents of section .text:
-// CHECK: 2000cccc cccccccc cccccccc cccccccc
-// CHECK: 20cccccc cccccccc cccccccc cccccccc
+// CHECK:      Contents of section .text:
+// CHECK-NEXT: 2000cccc cccccccc cccccccc cccccccc
+// CHECK-NEXT: 20cccccc cccccccc cccccccc cccccccc
+// CHECK-NEXT: e0ffcccc cccccccc cccccccc cccccccc
+// CHECK-NEXT: e0cccccc cccccccc cccccccc cccccccc
 
 .globl _start
 _start: