-- Best regards, LIU Hao From 1b92f8105dbece1694dd3ab398cfb5e3ce2c15d9 Mon Sep 17 00:00:00 2001 From: LIU Hao <lh_mo...@126.com> Date: Tue, 29 Apr 2025 10:43:06 +0800 Subject: [PATCH] i386/cygming: Decrease default preferred stack boundary for 32-bit targets This commit decreases the default preferred stack boundary to 4. In i386-options.cc, there's ix86_default_incoming_stack_boundary = PREFERRED_STACK_BOUNDARY; which sets the default incoming stack boundary to this value, if it's not overridden by other options or attributes. Previously, GCC preferred 16-byte alignment like other platforms, unless `-miamcu` was specified. However, the Microsoft x86 ABI only requires the stack be aligned to 4-byte boundaries. Callback functions from MSVC code may break this assumption by GCC (see reference below), causing local variables to be misaligned. Reference: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111107#c9 Signed-off-by: LIU Hao <lh_mo...@126.com> gcc/ChangeLog: PR 111107 * config/i386/cygming.h (PREFERRED_STACK_BOUNDARY_DEFAULT): Override definition from i386.h. --- gcc/config/i386/cygming.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/gcc/config/i386/cygming.h b/gcc/config/i386/cygming.h index 3ddcbecb22fd..b8c396d35793 100644 --- a/gcc/config/i386/cygming.h +++ b/gcc/config/i386/cygming.h @@ -28,6 +28,10 @@ along with GCC; see the file COPYING3. If not see #undef TARGET_SEH #define TARGET_SEH (TARGET_64BIT_MS_ABI && flag_unwind_tables) +#undef PREFERRED_STACK_BOUNDARY_DEFAULT +#define PREFERRED_STACK_BOUNDARY_DEFAULT \ + (TARGET_64BIT ? 128 : MIN_STACK_BOUNDARY) + /* Win64 with SEH cannot represent DRAP stack frames. Disable its use. Force the use of different mechanisms to allocate aligned local data. */ #undef MAX_STACK_ALIGNMENT -- 2.49.0
From 1b92f8105dbece1694dd3ab398cfb5e3ce2c15d9 Mon Sep 17 00:00:00 2001 From: LIU Hao <lh_mo...@126.com> Date: Tue, 29 Apr 2025 10:43:06 +0800 Subject: [PATCH] i386/cygming: Decrease default preferred stack boundary for 32-bit targets This commit decreases the default preferred stack boundary to 4. In i386-options.cc, there's ix86_default_incoming_stack_boundary = PREFERRED_STACK_BOUNDARY; which sets the default incoming stack boundary to this value, if it's not overridden by other options or attributes. Previously, GCC preferred 16-byte alignment like other platforms, unless `-miamcu` was specified. However, the Microsoft x86 ABI only requires the stack be aligned to 4-byte boundaries. Callback functions from MSVC code may break this assumption by GCC (see reference below), causing local variables to be misaligned. Reference: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111107#c9 Signed-off-by: LIU Hao <lh_mo...@126.com> gcc/ChangeLog: PR 111107 * config/i386/cygming.h (PREFERRED_STACK_BOUNDARY_DEFAULT): Override definition from i386.h. --- gcc/config/i386/cygming.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/gcc/config/i386/cygming.h b/gcc/config/i386/cygming.h index 3ddcbecb22fd..b8c396d35793 100644 --- a/gcc/config/i386/cygming.h +++ b/gcc/config/i386/cygming.h @@ -28,6 +28,10 @@ along with GCC; see the file COPYING3. If not see #undef TARGET_SEH #define TARGET_SEH (TARGET_64BIT_MS_ABI && flag_unwind_tables) +#undef PREFERRED_STACK_BOUNDARY_DEFAULT +#define PREFERRED_STACK_BOUNDARY_DEFAULT \ + (TARGET_64BIT ? 128 : MIN_STACK_BOUNDARY) + /* Win64 with SEH cannot represent DRAP stack frames. Disable its use. Force the use of different mechanisms to allocate aligned local data. */ #undef MAX_STACK_ALIGNMENT -- 2.49.0
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