builtins: Add __probestack support functions for x86

README.txt

@@ -196,6 +196,14 @@ long double _Complex __divtc3(long double a, long double b,
 
 // Runtime support
 
+// __probestack() is used to touch all pages of `size` bytes which will
+// later be allocated relative to the call site's stack pointer. It assumes
+// that the first and the last byte after the allocation will be touched by
+// something else. It has a custom platform specific calling convention.
+// This function is not available on Windows platforms as those have their
+// own builtins.
++void __probestack(du_int size);
+
 // __clear_cache() is used to tell process that new instructions have been
 // written to an address range. Necessary on processors that do not have
 // a unified instuction and data cache.

lib/builtins/CMakeLists.txt

@@ -140,6 +140,7 @@ set(x86_64_SOURCES
  x86_64/floatundidf.S
  x86_64/floatundisf.S
  x86_64/floatundixf.S
+ x86_64/probestack.S
  ${GENERIC_SOURCES})
 
 set(i386_SOURCES
@@ -155,6 +156,7 @@ set(i386_SOURCES
  i386/lshrdi3.S
  i386/moddi3.S
  i386/muldi3.S
+ i386/probestack.S
  i386/udivdi3.S
  i386/umoddi3.S
  ${GENERIC_SOURCES})

lib/builtins/i386/probestack.S

@@ -0,0 +1,54 @@
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+
+#include "../assembly.h"
+
+// void __probestack(du_int size);
+
+// `size` is passed in eax and this does not clobber any registers
+// including the parameter eax.
+
+#ifndef __WIN32__
+#ifdef __i386__
+
+#if defined(__APPLE__)
+ .const
+#elif defined(__ELF__)
+ .section .rodata
+#else
+ .section .rdata,"rd"
+#endif
+
+.text
+.balign 4
+DEFINE_COMPILERRT_FUNCTION(__probestack)
+.cfi_startproc
+ pushl %eax
+.cfi_adjust_cfa_offset 4
+.cfi_rel_offset %eax, 0
+ pushl %ecx
+.cfi_adjust_cfa_offset 4
+.cfi_rel_offset %ecx, 0
+ movl %esp, %ecx
+ subl $0x100C, %eax
+ jb 2f
+
+1:
+ subl $0x1000, %ecx
+ orb $0, (%ecx)
+ subl $0x1000, %eax
+ ja 1b
+
+2:
+ popl %ecx
+.cfi_adjust_cfa_offset -4
+.cfi_restore %ecx
+ popl %eax
+.cfi_adjust_cfa_offset -4
+.cfi_restore %eax
+ ret
+.cfi_endproc
+END_COMPILERRT_FUNCTION(__probestack)
+
+#endif // __i386__
+#endif // __WIN32__

lib/builtins/x86_64/probestack.S

@@ -0,0 +1,54 @@
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+
+#include "../assembly.h"
+
+// void __probestack(du_int size);
+
+// `size` is passed in rax and this does not clobber any registers
+// including the parameter rax.
+
+#ifndef __WIN32__
+#ifdef __x86_64__
+
+#if defined(__APPLE__)
+ .const
+#elif defined(__ELF__)
+ .section .rodata
+#else
+ .section .rdata,"rd"
+#endif
+
+.text
+.balign 4
+DEFINE_COMPILERRT_FUNCTION(__probestack)
+.cfi_startproc
+ pushq %rax
+.cfi_adjust_cfa_offset 8
+.cfi_rel_offset %rax, 0
+ pushq %r11
+.cfi_adjust_cfa_offset 8
+.cfi_rel_offset %r11, 0
+ movq %rsp, %r11
+ subq $0x1018, %rax
+ jb 2f
+
+1:
+ subq $0x1000, %r11
+ orb $0, (%r11)
+ subq $0x1000, %rax
+ ja 1b
+
+2:
+ popq %r11
+.cfi_adjust_cfa_offset -8
+.cfi_restore %r11
+ popq %rax
+.cfi_adjust_cfa_offset -8
+.cfi_restore %rax
+ ret
+.cfi_endproc
+END_COMPILERRT_FUNCTION(__probestack)
+
+#endif // __x86_64__
+#endif // __WIN32__