Summary: 64bit ASM can't have 32-bit stack operands
Version: D1 & D2
--- Comment #0 from Iain Buclaw <ibuc...@ubuntu.com> 2011-04-08 08:52:52 PDT ---
This is a question rolled into a report (it's affecting me, at least). This
excerpt (in core/thread.d for D2; in gc/gcx.d for D1 and D2) - the "push EAX"
instruction is not legal x86_64 asm code - according to the GNU 64bit
Assembler, which is strong enough an argument for me to follow - so is not
compilable with the GDC 64bit compiler (and maybe LDC too).
push RAX ;
push RBX ;
push RCX ;
push RDX ;
push RSI ;
push RDI ;
push RBP ;
push R8 ;
push R9 ;
push R10 ;
push R11 ;
push R12 ;
push R13 ;
push R14 ;
push R15 ;
--> push EAX ; // 16 byte align the stack <-- This line causes the error
mov sp[RBP],RSP ;
So, what to do?
Well, first I think druntime should consider revising this code for a start.
And secondly, DMD should be hardened to catch and disallow this.
Some thoughts for how to change it:
In 32bit mode:
pusha (afaik) saves (e)ax, cx, dx, bx, sp, bp, si, di
popa restores (e)di, si, bp, bx, dx, cx, ax (note, stack is not popped)
In GCC builtins:
unwind_init (what is currently being used in place of the above illegal code in
GDC) saves only the rbx, r12, r13, r14 and r15 registers.
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