invalid TLS with -relocation-model=pic -regalloc=local

[llvmbot]

Bugzilla Link	4004
Resolution	FIXED
Resolved on	Apr 24, 2009 08:02
Version	trunk
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@asl,@lattner,@sunfishcode

Extended Description

Compiling

@​a = thread_local global i32 0 ; <i32*> [#uses=2]

define void @​f(i32* nocapture %c, i32* nocapture %d) nounwind optsize {
entry:
%0 = load i32* @​a, align 4 ; [#uses=1]
store i32 %0, i32* %c, align 4
%1 = load i32* @​a, align 4 ; [#uses=1]
store i32 %1, i32* %d, align 4
ret void
}

with llc -relocation-model=pic -regalloc=local produces

    .byte   0x66; leaq      a@TLSGD(%rip), %rdi; .word      0x6666; rex64
    movq    %rax, -8(%rsp)
    movq    %rcx, -16(%rsp)
    call    __tls_get_addr@PLT

This is invalid. The call must be just after the rex64.

I think this is a more general problem with the local register allocator. It is inserting spills between two instructions linked by a flag.

[asl]

Note: the testcase should use x86-64/linux target triple

[lattner]

The issue here is that machineinstrs are assumed to not have code layout dependencies between them.

The best way to handle this is to pull the call into the TLS magic instruction. Instead of being just:

byte 0x66; leaq a@TLSGD(%rip), %rdi; .word 0x6666; rex64

You'd also have a call in that too.

[llvmbot]

Fixed on revision 69968.