thread local variables don't work with static executables

[andrewrk]

before 5d2edac:

$ ./zig test ../test/stage1/behavior.zig --static
Test 384/579 behavior.misc.thread local variable...test failure
/home/andy/downloads/zig/build-llvm8/lib/zig/std/testing.zig:146:14: 0x22202c in ??? (test)
    if (!ok) @panic("test failure");
             ^
/home/andy/downloads/zig/test/stage1/behavior/misc.zig:695:11: 0x22cbe6 in ??? (test)
    expect(S.t == 1235);
          ^

after, I'm disabling the failing test with a TODO comment and a link to this issue.

[andrewrk]

Here's the difference in code generation between static and PIC:

threadlocal var x: i32 = 1234;

export fn read_it() i32 {
    return x;
}
export fn write_it(y: i32) void {
    x = y;
}

--- test-static.s       2019-04-03 22:10:40.343823505 -0400
+++ test-pic.s  2019-04-03 22:10:29.016752536 -0400
@@ -14,18 +14,27 @@
 0000000000000010 <read_it>:
   10:  55                      push   %rbp
   11:  48 89 e5                mov    %rsp,%rbp
-  14:  64 8b 04 25 00 00 00    mov    %fs:0x0,%eax
-  1b:  00 
-  1c:  5d                      pop    %rbp
-  1d:  c3                      retq   
-  1e:  66 90                   xchg   %ax,%ax
+  14:  48 8d 3d 00 00 00 00    lea    0x0(%rip),%rdi        # 1b <read_it+0xb>
+  1b:  e8 00 00 00 00          callq  20 <read_it+0x10>
+  20:  8b 80 00 00 00 00       mov    0x0(%rax),%eax
+  26:  5d                      pop    %rbp
+  27:  c3                      retq   
+  28:  0f 1f 84 00 00 00 00    nopl   0x0(%rax,%rax,1)
+  2f:  00 
 
-0000000000000020 <write_it>:
-  20:  55                      push   %rbp
-  21:  48 89 e5                mov    %rsp,%rbp
-  24:  89 7d fc                mov    %edi,-0x4(%rbp)
-  27:  8b 7d fc                mov    -0x4(%rbp),%edi
-  2a:  64 89 3c 25 00 00 00    mov    %edi,%fs:0x0
-  31:  00 
-  32:  5d                      pop    %rbp
-  33:  c3                      retq   
+0000000000000030 <write_it>:
+  30:  55                      push   %rbp
+  31:  48 89 e5                mov    %rsp,%rbp
+  34:  53                      push   %rbx
+  35:  50                      push   %rax
+  36:  89 7d f4                mov    %edi,-0xc(%rbp)
+  39:  8b 7d f4                mov    -0xc(%rbp),%edi
+  3c:  89 7d f0                mov    %edi,-0x10(%rbp)
+  3f:  48 8d 3d 00 00 00 00    lea    0x0(%rip),%rdi        # 46 <write_it+0x16>
+  46:  e8 00 00 00 00          callq  4b <write_it+0x1b>
+  4b:  8b 5d f0                mov    -0x10(%rbp),%ebx
+  4e:  89 98 00 00 00 00       mov    %ebx,0x0(%rax)
+  54:  48 83 c4 08             add    $0x8,%rsp
+  58:  5b                      pop    %rbx
+  59:  5d                      pop    %rbp
+  5a:  c3                      retq   

I think this needs to be linked for it to make sense.

[andrewrk]

OK when building an exe:
static:

0000000000201050 <read_it>:
  201050:	55                   	push   %rbp
  201051:	48 89 e5             	mov    %rsp,%rbp
  201054:	64 8b 04 25 fc ff ff 	mov    %fs:0xfffffffffffffffc,%eax
  20105b:	ff 
  20105c:	5d                   	pop    %rbp
  20105d:	c3                   	retq   
  20105e:	66 90                	xchg   %ax,%ax

0000000000201060 <write_it>:
  201060:	55                   	push   %rbp
  201061:	48 89 e5             	mov    %rsp,%rbp
  201064:	89 7d fc             	mov    %edi,-0x4(%rbp)
  201067:	8b 7d fc             	mov    -0x4(%rbp),%edi
  20106a:	64 89 3c 25 fc ff ff 	mov    %edi,%fs:0xfffffffffffffffc
  201071:	ff 
  201072:	5d                   	pop    %rbp
  201073:	c3                   	retq   
  201074:	66 2e 0f 1f 84 00 00 	nopw   %cs:0x0(%rax,%rax,1)
  20107b:	00 00 00 
  20107e:	66 90                	xchg   %ax,%ax

pic:

0000000000201040 <read_it>:
  201040:	55                   	push   %rbp
  201041:	48 89 e5             	mov    %rsp,%rbp
  201044:	66 66 66 64 48 8b 04 	data16 data16 data16 mov %fs:0x0,%rax
  20104b:	25 00 00 00 00 
  201050:	8b 80 fc ff ff ff    	mov    -0x4(%rax),%eax
  201056:	5d                   	pop    %rbp
  201057:	c3                   	retq   
  201058:	0f 1f 84 00 00 00 00 	nopl   0x0(%rax,%rax,1)
  20105f:	00 

0000000000201060 <write_it>:
  201060:	55                   	push   %rbp
  201061:	48 89 e5             	mov    %rsp,%rbp
  201064:	53                   	push   %rbx
  201065:	50                   	push   %rax
  201066:	89 7d f4             	mov    %edi,-0xc(%rbp)
  201069:	8b 7d f4             	mov    -0xc(%rbp),%edi
  20106c:	89 7d f0             	mov    %edi,-0x10(%rbp)
  20106f:	66 66 66 64 48 8b 04 	data16 data16 data16 mov %fs:0x0,%rax
  201076:	25 00 00 00 00 
  20107b:	8b 5d f0             	mov    -0x10(%rbp),%ebx
  20107e:	89 98 fc ff ff ff    	mov    %ebx,-0x4(%rax)
  201084:	48 83 c4 08          	add    $0x8,%rsp
  201088:	5b                   	pop    %rbx
  201089:	5d                   	pop    %rbp
  20108a:	c3                   	retq   
  20108b:	0f 1f 44 00 00       	nopl   0x0(%rax,%rax,1)