On Tue, Oct 31, 2017 at 3:09 AM, Daniel Santos <daniel.san...@pobox.com> wrote:
> When we are realigning the stack pointer, making an ms_abi to sysv_abi
> call and alllocating 2GiB or more on the stack we end up with an invalid
> INSN due to a non-immediate offset. This occurs both with and without
> -mcall-ms2sysv-xlogues. Additionally, I've discovered that the stack
> allocation with -mcall-ms2sysv-xlogues is incorrect as it ignores stack
> checking, stack clash checking and probing.
>
> This patch fixes these problems by
>
> 1. No longer allocate stack space in ix86_emit_outlined_ms2sysv_save.
> 2. Rearrange where we emit SSE saves or stub call:
> a. Before frame allocation when offset from frame to save area is >= 2GiB.
> b. After frame allocation when frame is < 2GiB. (Stack allocations
> prior to the stub call can't be combined with those afterwards, so
> this is better when possible.)
> 3. Modify choose_baseaddr to take an optional scratch_regno argument
> and never return rtx that cannot be used as an immediate.
>
> gcc:
> config/i386/i386.c (choose_basereg): Use optional scratch
> register and add assertion.
> (x86_emit_outlined_ms2sysv_save): use scratch register when
> needed, and don't allocate stack.
> (ix86_expand_prologue): Rearrange where SSE saves/stub call is
> emitted, correct wrong allocation with -mcall-ms2sysv-xlogues.
> (ix86_emit_outlined_ms2sysv_restore): Fix non-immediate offsets.
>
> gcc/testsuite:
> gcc.target/i386/pr82002-2a.c: Change from xfail to fail.
> gcc.target/i386/pr82002-2b.c: Likewise.
>
> Signed-off-by: Daniel Santos <daniel.san...@pobox.com>
> ---
> gcc/config/i386/i386.c | 76
> ++++++++++++++++++++++++------
> gcc/testsuite/gcc.target/i386/pr82002-2a.c | 2 -
> gcc/testsuite/gcc.target/i386/pr82002-2b.c | 2 -
> 3 files changed, 62 insertions(+), 18 deletions(-)
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 83a07afb3e1..abd8e937e0d 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -11520,7 +11520,8 @@ choose_basereg (HOST_WIDE_INT cfa_offset, rtx
> &base_reg,
> The valid base registers are taken from CFUN->MACHINE->FS. */
>
> static rtx
> -choose_baseaddr (HOST_WIDE_INT cfa_offset, unsigned int *align)
> +choose_baseaddr (HOST_WIDE_INT cfa_offset, unsigned int *align,
> + int scratch_regno = -1)
> {
> rtx base_reg = NULL;
> HOST_WIDE_INT base_offset = 0;
> @@ -11534,6 +11535,28 @@ choose_baseaddr (HOST_WIDE_INT cfa_offset, unsigned
> int *align)
> choose_basereg (cfa_offset, base_reg, base_offset, 0, align);
>
> gcc_assert (base_reg != NULL);
> +
> + if (TARGET_64BIT)
> + {
> + rtx base_offset_rtx = GEN_INT (base_offset);
> +
> + if (scratch_regno >= 0)
> + {
> + if (!x86_64_immediate_operand (base_offset_rtx, DImode))
> + {
> + rtx tmp;
> + rtx scratch_reg = gen_rtx_REG (DImode, scratch_regno);
> +
> + emit_insn (gen_rtx_SET (scratch_reg, base_offset_rtx));
> + tmp = gen_rtx_PLUS (DImode, scratch_reg, base_reg);
> + emit_insn (gen_rtx_SET (scratch_reg, tmp));
> + return scratch_reg;
> + }
> + }
> + else
> + gcc_assert (x86_64_immediate_operand (base_offset_rtx, DImode));
> + }
> +
> return plus_constant (Pmode, base_reg, base_offset);
> }
This function doesn't need to return a register, it can return plus
RTX. I'd suggest the following implementation:
--cut here--
Index: i386.c
===================================================================
--- i386.c (revision 254243)
+++ i386.c (working copy)
@@ -11520,7 +11520,8 @@
The valid base registers are taken from CFUN->MACHINE->FS. */
static rtx
-choose_baseaddr (HOST_WIDE_INT cfa_offset, unsigned int *align)
+choose_baseaddr (HOST_WIDE_INT cfa_offset, unsigned int *align,
+ unsigned int scratch_regno = INVALID_REGNUM)
{
rtx base_reg = NULL;
HOST_WIDE_INT base_offset = 0;
@@ -11534,6 +11535,19 @@
choose_basereg (cfa_offset, base_reg, base_offset, 0, align);
gcc_assert (base_reg != NULL);
+
+ rtx base_offset_rtx = GEN_INT (base_offset);
+
+ if (!x86_64_immediate_operand (base_offset_rtx, Pmode))
+ {
+ gcc_assert (scratch_regno != INVALID_REGNUM);
+
+ rtx scratch_reg = gen_rtx_REG (Pmode, scratch_regno);
+ emit_move_insn (scratch_reg, base_offset_rtx);
+
+ return gen_rtx_PLUS (Pmode, base_reg, scratch_reg);
+ }
+
return plus_constant (Pmode, base_reg, base_offset);
}
--cut here--
You have to always return Pmode, otherwise x32 will complain (you may
try with -maddress-mode=short). Also, the above will immediately ICE
when too large base_offset is used without the scratch, so one can
backtrace to offending function.
> @@ -12793,23 +12816,22 @@ ix86_emit_outlined_ms2sysv_save (const struct
> ix86_frame &frame)
> rtx sym, addr;
> rtx rax = gen_rtx_REG (word_mode, AX_REG);
> const struct xlogue_layout &xlogue = xlogue_layout::get_instance ();
> - HOST_WIDE_INT allocate = frame.stack_pointer_offset - m->fs.sp_offset;
>
> /* AL should only be live with sysv_abi. */
> gcc_assert (!ix86_eax_live_at_start_p ());
> + gcc_assert (m->fs.sp_offset >= frame.sse_reg_save_offset);
>
> /* Setup RAX as the stub's base pointer. We use stack_realign_offset
> rather
> we've actually realigned the stack or not. */
> align = GET_MODE_ALIGNMENT (V4SFmode);
> addr = choose_baseaddr (frame.stack_realign_offset
> - + xlogue.get_stub_ptr_offset (), &align);
> + + xlogue.get_stub_ptr_offset (), &align, AX_REG);
> gcc_assert (align >= GET_MODE_ALIGNMENT (V4SFmode));
> - emit_insn (gen_rtx_SET (rax, addr));
>
> - /* Allocate stack if not already done. */
> - if (allocate > 0)
> - pro_epilogue_adjust_stack (stack_pointer_rtx, stack_pointer_rtx,
> - GEN_INT (-allocate), -1, false);
> + /* If choose_baseaddr returned our scratch register, then we don't need to
> + do another SET. */
> + if (!REG_P (addr) || REGNO (addr) != AX_REG)
> + emit_insn (gen_rtx_SET (rax, addr));
You won't need the above change with a choose_baseaddr that returns PLUS RTX.
> /* Get the stub symbol. */
> sym = xlogue.get_stub_rtx (frame_pointer_needed ? XLOGUE_STUB_SAVE_HFP
> @@ -12841,6 +12863,7 @@ ix86_expand_prologue (void)
> HOST_WIDE_INT allocate;
> bool int_registers_saved;
> bool sse_registers_saved;
> + bool save_stub_call_needed;
> rtx static_chain = NULL_RTX;
>
> if (ix86_function_naked (current_function_decl))
> @@ -13016,6 +13039,8 @@ ix86_expand_prologue (void)
>
> int_registers_saved = (frame.nregs == 0);
> sse_registers_saved = (frame.nsseregs == 0);
> + save_stub_call_needed = (m->call_ms2sysv);
> + gcc_assert (!(!sse_registers_saved && save_stub_call_needed));
Oooh, double negation :(
> if (frame_pointer_needed && !m->fs.fp_valid)
> {
> @@ -13110,10 +13135,27 @@ ix86_expand_prologue (void)
> target. */
> if (TARGET_SEH)
> m->fs.sp_valid = false;
> - }
>
> - if (m->call_ms2sysv)
> - ix86_emit_outlined_ms2sysv_save (frame);
> + /* If SP offset is non-immediate after allocation of the stack frame,
> + then emit SSE saves or stub call prior to allocating the rest of the
> + stack frame. This is less efficient for the out-of-line stub because
> + we can't combine allocations across the call barrier, but it's better
> + than using a scratch register. */
> + else if (frame.stack_pointer_offset - m->fs.sp_realigned_offset
> + > 0x7fffffff)
Should we use x86_64_immediate_operand here that betters document the
limitation instead of using magic constants?
> + {
> + if (!sse_registers_saved)
> + {
> + ix86_emit_save_sse_regs_using_mov (frame.sse_reg_save_offset);
> + sse_registers_saved = true;
> + }
> + else if (save_stub_call_needed)
> + {
> + ix86_emit_outlined_ms2sysv_save (frame);
> + save_stub_call_needed = false;
> + }
> + }
> + }
>
> allocate = frame.stack_pointer_offset - m->fs.sp_offset;
>
> @@ -13337,6 +13379,8 @@ ix86_expand_prologue (void)
> ix86_emit_save_regs_using_mov (frame.reg_save_offset);
> if (!sse_registers_saved)
> ix86_emit_save_sse_regs_using_mov (frame.sse_reg_save_offset);
> + else if (save_stub_call_needed)
> + ix86_emit_outlined_ms2sysv_save (frame);
>
> /* For the mcount profiling on 32 bit PIC mode we need to emit SET_GOT
> in PROLOGUE. */
> @@ -13560,7 +13604,7 @@ ix86_emit_outlined_ms2sysv_restore (const struct
> ix86_frame &frame,
> rtvec v;
> unsigned int elems_needed, align, i, vi = 0;
> rtx_insn *insn;
> - rtx sym, tmp;
> + rtx sym, addr, tmp;
> rtx rsi = gen_rtx_REG (word_mode, SI_REG);
> rtx r10 = NULL_RTX;
> const struct xlogue_layout &xlogue = xlogue_layout::get_instance ();
> @@ -13577,9 +13621,13 @@ ix86_emit_outlined_ms2sysv_restore (const struct
> ix86_frame &frame,
>
> /* Setup RSI as the stub's base pointer. */
> align = GET_MODE_ALIGNMENT (V4SFmode);
> - tmp = choose_baseaddr (rsi_offset, &align);
> + addr = choose_baseaddr (rsi_offset, &align, SI_REG);
> gcc_assert (align >= GET_MODE_ALIGNMENT (V4SFmode));
> - emit_insn (gen_rtx_SET (rsi, tmp));
> +
> + /* If choose_baseaddr returned our scratch register, then we don't need to
> + do another SET. */
> + if (!REG_P (addr) || REGNO (addr) != SI_REG)
> + emit_insn (gen_rtx_SET (rsi, addr));
Again, no need for these changes with the above implementation of
choose_baseaddr.
> /* Get a symbol for the stub. */
> if (frame_pointer_needed)
> diff --git a/gcc/testsuite/gcc.target/i386/pr82002-2a.c
> b/gcc/testsuite/gcc.target/i386/pr82002-2a.c
> index bc85080ba8e..c31440debe2 100644
> --- a/gcc/testsuite/gcc.target/i386/pr82002-2a.c
> +++ b/gcc/testsuite/gcc.target/i386/pr82002-2a.c
> @@ -1,7 +1,5 @@
> /* { dg-do compile { target lp64 } } */
> /* { dg-options "-Ofast -mstackrealign -mabi=ms" } */
> -/* { dg-xfail-if "" { *-*-* } } */
> -/* { dg-xfail-run-if "" { *-*-* } } */
>
> void __attribute__((sysv_abi)) a (char *);
> void
> diff --git a/gcc/testsuite/gcc.target/i386/pr82002-2b.c
> b/gcc/testsuite/gcc.target/i386/pr82002-2b.c
> index 10e44cd7b1d..939e069517d 100644
> --- a/gcc/testsuite/gcc.target/i386/pr82002-2b.c
> +++ b/gcc/testsuite/gcc.target/i386/pr82002-2b.c
> @@ -1,7 +1,5 @@
> /* { dg-do compile { target lp64 } } */
> /* { dg-options "-Ofast -mstackrealign -mabi=ms -mcall-ms2sysv-xlogues" } */
> -/* { dg-xfail-if "" { *-*-* } } */
> -/* { dg-xfail-run-if "" { *-*-* } } */
>
> void __attribute__((sysv_abi)) a (char *);
> void
> --
> 2.14.3
>
