winnt.c (i386_pe_seh_end_prologue): Move code to ...

[gcc.git] / gcc / config / i386 / i386.h

diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index f7f13d20cdcb91c48fb17b201fedd55cb597fd53..18633faa90aacf7cc842f69e998e7b3d0f62e900 100644 (file)
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -729,6 +729,18 @@ enum target_cpu_default
 /* Boundary (in *bits*) on which the incoming stack is aligned.  */
 #define INCOMING_STACK_BOUNDARY ix86_incoming_stack_boundary
 
+/* According to Windows x64 software convention, the maximum stack allocatable
+   in the prologue is 4G - 8 bytes.  Furthermore, there is a limited set of
+   instructions allowed to adjust the stack pointer in the epilog, forcing the
+   use of frame pointer for frames larger than 2 GB.  This theorical limit
+   is reduced by 256, an over-estimated upper bound for the stack use by the
+   prologue.
+   We define only one threshold for both the prolog and the epilog.  When the
+   frame size is larger than this threshold, we allocate the are to save SSE
+   regs, then save them, and then allocate the remaining.  There is no SEH
+   unwind info for this later allocation.  */
+#define SEH_MAX_FRAME_SIZE ((2U << 30) - 256)
+
 /* Target OS keeps a vector-aligned (128-bit, 16-byte) stack.  This is
    mandatory for the 64-bit ABI, and may or may not be true for other
    operating systems.  */