x86-64: Fix TLSDESC relaxation for x32

For x32, we must encode "lea x@TLSDESC(%rip), %reg" with a REX prefix
even if it isn't required.  Otherwise linker can’t safely perform
GDesc -> IE/LE optimization.  X32 TLSDESC sequences can be:

40 8d 05 00 00 00 00	rex lea	x@TLSDESC(%rip), %reg
...
67 ff 10		call	*x@TLSCALL(%eax)

or the same sequence as LP64:

48 8d 05 00 00 00 00	lea	foo@TLSDESC(%rip), %reg
...
ff 10			call	*foo@TLSCALL(%rax)

We need to support both sequences for x32.  For both GDesc -> IE/LE
transitions,

67 ff 10		call	*x@TLSCALL(%eax)

should relaxed to

0f 1f 00		nopl	(%rax)

For GDesc -> LE transition,

40 8d 05 00 00 00 00	rex lea	x@TLSDESC(%rip), %reg

should relaxed to

40 c7 c0 fc ff ff ff	rex movl $x@tpoff, %reg

For GDesc -> IE transition,

40 8d 05 00 00 00 00	rex lea	x@TLSDESC(%rip), %reg

should relaxed to

40 8b 05 00 00 00 00	rex movl x@gottpoff(%rip), %eax

bfd/

	PR ld/25416
	* elf64-x86-64.c (elf_x86_64_check_tls_transition): Support
	"rex leal x@tlsdesc(%rip), %reg" and "call *x@tlsdesc(%eax)" in
	X32 mode.
	(elf_x86_64_relocate_section): In x32 mode, for GDesc -> LE
	transition, relax "rex leal x@tlsdesc(%rip), %reg" to
	"rex movl $x@tpoff, %reg", for GDesc -> IE transition, relax
	"rex leal x@tlsdesc(%rip), %reg" to
	"rex movl x@gottpoff(%rip), %eax".  For both transitions, relax
	"call *(%eax)" to "nopl (%rax)".

gas/

	PR ld/25416
	* config/tc-i386.c (output_insn): Add a dummy REX_OPCODE prefix
	for lea with R_X86_64_GOTPC32_TLSDESC relocation when generating
	x32 object.
	* testsuite/gas/i386/ilp32/x32-tls.d: Updated.
	* testsuite/gas/i386/ilp32/x32-tls.s: Add tests for lea with
	R_X86_64_GOTPC32_TLSDESC relocation.

ld/

	PR ld/25416
	* testsuite/ld-x86-64/pr25416-1.s: New file
	* testsuite/ld-x86-64/pr25416-1a.d: Likewise.
	* testsuite/ld-x86-64/pr25416-1b.d: Likewise.
	* testsuite/ld-x86-64/pr25416-1.s: Likewise.
	* testsuite/ld-x86-64/pr25416-2.s: Likewise.
	* testsuite/ld-x86-64/pr25416-2a.d: Likewise.
	* testsuite/ld-x86-64/pr25416-2b.d: Likewise.
	* testsuite/ld-x86-64/pr25416-3.d: Likewise.
	* testsuite/ld-x86-64/pr25416-3.s: Likewise.
	* testsuite/ld-x86-64/pr25416-4.d: Likewise.
	* testsuite/ld-x86-64/pr25416-4.s: Likewise.
	* testsuite/ld-x86-64/pr25416-5a.c: Likewise.
	* testsuite/ld-x86-64/pr25416-5b.s: Likewise.
	* testsuite/ld-x86-64/pr25416-5c.s: Likewise.
	* testsuite/ld-x86-64/pr25416-5d.s: Likewise.
	* testsuite/ld-x86-64/pr25416-5e.s: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run PR ld/25416 tests.

4 files changed, 19 insertions, 2 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 426e484..0220948 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,13 @@
+2020-01-20  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/25416
+	* config/tc-i386.c (output_insn): Add a dummy REX_OPCODE prefix
+	for lea with R_X86_64_GOTPC32_TLSDESC relocation when generating
+	x32 object.
+	* testsuite/gas/i386/ilp32/x32-tls.d: Updated.
+	* testsuite/gas/i386/ilp32/x32-tls.s: Add tests for lea with
+	R_X86_64_GOTPC32_TLSDESC relocation.
+
 2020-01-18  Nick Clifton  <nickc@redhat.com>
 
 	* configure: Regenerate.
diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index 8728725..87ab43b 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -8713,10 +8713,13 @@ output_insn (void)
 #if defined (OBJ_MAYBE_ELF) || defined (OBJ_ELF)
 	  /* For x32, add a dummy REX_OPCODE prefix for mov/add with
 	     R_X86_64_GOTTPOFF relocation so that linker can safely
-	     perform IE->LE optimization.  */
+	     perform IE->LE optimization.  A dummy REX_OPCODE prefix
+	     is also needed for lea with R_X86_64_GOTPC32_TLSDESC
+	     relocation for GDesc -> IE/LE optimization.  */
 	  if (x86_elf_abi == X86_64_X32_ABI
 	      && i.operands == 2
-	      && i.reloc[0] == BFD_RELOC_X86_64_GOTTPOFF
+	      && (i.reloc[0] == BFD_RELOC_X86_64_GOTTPOFF
+		  || i.reloc[0] == BFD_RELOC_X86_64_GOTPC32_TLSDESC)
 	      && i.prefix[REX_PREFIX] == 0)
 	    add_prefix (REX_OPCODE);
 #endif
diff --git a/gas/testsuite/gas/i386/ilp32/x32-tls.d b/gas/testsuite/gas/i386/ilp32/x32-tls.d
index 1255829..ab4da5c 100644
--- a/gas/testsuite/gas/i386/ilp32/x32-tls.d
+++ b/gas/testsuite/gas/i386/ilp32/x32-tls.d
@@ -10,4 +10,6 @@ Disassembly of section .text:
 [ 	]*[a-f0-9]+:	4c 8b 25 00 00 00 00 	mov    0x0\(%rip\),%r12        # e <_start\+0xe>
 [ 	]*[a-f0-9]+:	40 03 05 00 00 00 00 	rex add 0x0\(%rip\),%eax        # 15 <_start\+0x15>
 [ 	]*[a-f0-9]+:	44 03 25 00 00 00 00 	add    0x0\(%rip\),%r12d        # 1c <_start\+0x1c>
+[ 	]*[a-f0-9]+:	40 8d 05 00 00 00 00 	rex lea 0x0\(%rip\),%eax        # 23 <_start\+0x23>
+[ 	]*[a-f0-9]+:	44 8d 25 00 00 00 00 	lea    0x0\(%rip\),%r12d        # 2a <_start\+0x2a>
 #pass
diff --git a/gas/testsuite/gas/i386/ilp32/x32-tls.s b/gas/testsuite/gas/i386/ilp32/x32-tls.s
index f9626cd..e1599be 100644
--- a/gas/testsuite/gas/i386/ilp32/x32-tls.s
+++ b/gas/testsuite/gas/i386/ilp32/x32-tls.s
@@ -4,6 +4,8 @@ _start:
 	mov	foo@gottpoff(%rip), %r12
 	add	foo@gottpoff(%rip), %eax
 	add	foo@gottpoff(%rip), %r12d
+	lea	foo@tlsdesc(%rip), %eax
+	lea	foo@tlsdesc(%rip), %r12d
 	.globl	foo
 	.section	.tdata,"awT",@progbits
 	.align 4