ld/x86-64: Add PR gold/26939 tests

GOTPCRELX relocations can be transformed only when addend == -4.  Add
tests for GOTPCRELX relocations with addend != -4.

	PR gold/26939
	* testsuite/ld-x86-64/pr26939-x32.d: New file.
	* testsuite/ld-x86-64/pr26939.d: Likewise.
	* testsuite/ld-x86-64/pr26939.s: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run PR gold/26939 tests.

ld/ChangeLog

@@ -1,3 +1,11 @@
+2020-11-24  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR gold/26939
+	* testsuite/ld-x86-64/pr26939-x32.d: New file.
+	* testsuite/ld-x86-64/pr26939.d: Likewise.
+	* testsuite/ld-x86-64/pr26939.s: Likewise.
+	* testsuite/ld-x86-64/x86-64.exp: Run PR gold/26939 tests.
+
 2020-11-23  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/26918

ld/testsuite/ld-x86-64/pr26939-x32.d

@@ -0,0 +1,13 @@
+#source: pr26939.s
+#as: --x32
+#ld: -pie -melf32_x86_64
+#objdump: -dw
+
+.*: +file format .*
+
+
+Disassembly of section .text:
+
+#...
+[ 	]*[a-f0-9]+:	8b 05 ([0-9a-f]{2} ){4} *	mov    0x[a-f0-9]+\(%rip\),%eax        # [a-f0-9]+ <.*>
+#pass

ld/testsuite/ld-x86-64/pr26939.d

@@ -0,0 +1,12 @@
+#as: --64
+#ld: -pie -melf_x86_64
+#objdump: -dw
+
+.*: +file format .*
+
+
+Disassembly of section .text:
+
+#...
+[ 	]*[a-f0-9]+:	8b 05 ([0-9a-f]{2} ){4} *	mov    0x[a-f0-9]+\(%rip\),%eax        # [a-f0-9]+ <.*>
+#pass

ld/testsuite/ld-x86-64/pr26939.s

@@ -0,0 +1,5 @@
+	.text
+	.globl	_start
+	.type	_start,@function
+_start:
+	movl	_start@GOTPCREL+4(%rip), %eax

ld/testsuite/ld-x86-64/x86-64.exp

@@ -659,6 +659,8 @@ run_dump_test "pr20253-5b"
 run_dump_test "tlsdesc2"
 run_dump_test "pr22048"
 run_dump_test "pr22929"
+run_dump_test "pr26939"
+run_dump_test "pr26939-x32"
 
 proc undefined_weak {cflags ldflags} {
     set testname "Undefined weak symbol"