1*7c3d14c8STreehugger Robot// This file is dual licensed under the MIT and the University of Illinois Open 2*7c3d14c8STreehugger Robot// Source Licenses. See LICENSE.TXT for details. 3*7c3d14c8STreehugger Robot 4*7c3d14c8STreehugger Robot#include "../assembly.h" 5*7c3d14c8STreehugger Robot 6*7c3d14c8STreehugger Robot#ifdef __x86_64__ 7*7c3d14c8STreehugger Robot 8*7c3d14c8STreehugger Robot// _chkstk (_alloca) routine - probe stack between %rsp and (%rsp-%rax) in 4k increments, 9*7c3d14c8STreehugger Robot// then decrement %rsp by %rax. Preserves all registers except %rsp and flags. 10*7c3d14c8STreehugger Robot// This routine is windows specific 11*7c3d14c8STreehugger Robot// http://msdn.microsoft.com/en-us/library/ms648426.aspx 12*7c3d14c8STreehugger Robot 13*7c3d14c8STreehugger Robot.text 14*7c3d14c8STreehugger Robot.balign 4 15*7c3d14c8STreehugger RobotDEFINE_COMPILERRT_FUNCTION(__alloca) 16*7c3d14c8STreehugger Robot mov %rcx,%rax // x64 _alloca is a normal function with parameter in rcx 17*7c3d14c8STreehugger Robot // fallthrough 18*7c3d14c8STreehugger RobotDEFINE_COMPILERRT_FUNCTION(___chkstk) 19*7c3d14c8STreehugger Robot push %rcx 20*7c3d14c8STreehugger Robot cmp $0x1000,%rax 21*7c3d14c8STreehugger Robot lea 16(%rsp),%rcx // rsp before calling this routine -> rcx 22*7c3d14c8STreehugger Robot jb 1f 23*7c3d14c8STreehugger Robot2: 24*7c3d14c8STreehugger Robot sub $0x1000,%rcx 25*7c3d14c8STreehugger Robot test %rcx,(%rcx) 26*7c3d14c8STreehugger Robot sub $0x1000,%rax 27*7c3d14c8STreehugger Robot cmp $0x1000,%rax 28*7c3d14c8STreehugger Robot ja 2b 29*7c3d14c8STreehugger Robot1: 30*7c3d14c8STreehugger Robot sub %rax,%rcx 31*7c3d14c8STreehugger Robot test %rcx,(%rcx) 32*7c3d14c8STreehugger Robot 33*7c3d14c8STreehugger Robot lea 8(%rsp),%rax // load pointer to the return address into rax 34*7c3d14c8STreehugger Robot mov %rcx,%rsp // install the new top of stack pointer into rsp 35*7c3d14c8STreehugger Robot mov -8(%rax),%rcx // restore rcx 36*7c3d14c8STreehugger Robot push (%rax) // push return address onto the stack 37*7c3d14c8STreehugger Robot sub %rsp,%rax // restore the original value in rax 38*7c3d14c8STreehugger Robot ret 39*7c3d14c8STreehugger RobotEND_COMPILERRT_FUNCTION(___chkstk) 40*7c3d14c8STreehugger RobotEND_COMPILERRT_FUNCTION(__alloca) 41*7c3d14c8STreehugger Robot 42*7c3d14c8STreehugger Robot#endif // __x86_64__ 43