Hi
On 02/11/18 18:37, Sudakshina Das wrote:
> Hi
>
> This patch is part of a series that enables ARMv8.5-A in GCC and
> adds Branch Target Identification Mechanism.
> (https://developer.arm.com/products/architecture/cpu-architecture/a-profile/exploration-tools)
>
> This patch changes the registers that are allowed for indirect tail
> calls. We are choosing to restrict these to only x16 or x17.
>
> Indirect tail calls are special in a way that they convert a call
> statement (BLR instruction) to a jump statement (BR instruction). For
> the best possible use of Branch Target Identification Mechanism, we
> would like to place a "BTI C" (call) at the beginning of the function
> which is only compatible with BLRs and BR X16/X17. In order to make
> indirect tail calls compatible with this scenario, we are restricting
> the TAILCALL_ADDR_REGS.
>
> In order to use x16/x17 for this purpose, we also had to change the use
> of these registers in the epilogue/prologue handling. For this purpose
> we are now using x12 and x13 named as EP0_REGNUM and EP1_REGNUM as
> scratch registers for epilogue and prologue.
>
> Bootstrapped and regression tested with aarch64-none-linux-gnu. Updated
> test. Ran Spec2017 and no performance hit.
>
> Is this ok for trunk?
>
> Thanks
> Sudi
>
>
> *** gcc/ChangeLog***
>
> 2018-xx-xx Sudakshina Das <[email protected]>
>
> * config/aarch64/aarch64.c (aarch64_expand_prologue): Use new
> epilogue/prologue scratch registers EP0_REGNUM and EP1_REGNUM.
> (aarch64_expand_epilogue): Likewise.
> (aarch64_output_mi_thunk): Likewise
> * config/aarch64/aarch64.h (REG_CLASS_CONTENTS): Change
> TAILCALL_ADDR_REGS
> to x16 and x17.
> * config/aarch64/aarch64.md: Define EP0_REGNUM and EP1_REGNUM.
>
> *** gcc/testsuite/ChangeLog ***
>
> 2018-xx-xx Sudakshina Das <[email protected]>
>
> * gcc.target/aarch64/test_frame_17.c: Update to check for
> EP0_REGNUM instead of IP0_REGNUM and add test case.
>
I have edited the patch to take out a change that was not needed as part
of this patch in aarch64_expand_epilogue. The only change now happening
there is as mentioned in the ChangeLog to replace the uses of IP0/IP1.
ChangeLog still applies.
Thanks
Sudi
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 4bec6bd963d91c475a4e18f883955093e9268cfd..cc95be32d40268d3647c8280188f17ff8212a156 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -586,7 +586,7 @@ enum reg_class
#define REG_CLASS_CONTENTS \
{ \
{ 0x00000000, 0x00000000, 0x00000000 }, /* NO_REGS */ \
- { 0x0004ffff, 0x00000000, 0x00000000 }, /* TAILCALL_ADDR_REGS */\
+ { 0x00030000, 0x00000000, 0x00000000 }, /* TAILCALL_ADDR_REGS */\
{ 0x7fffffff, 0x00000000, 0x00000003 }, /* GENERAL_REGS */ \
{ 0x80000000, 0x00000000, 0x00000000 }, /* STACK_REG */ \
{ 0xffffffff, 0x00000000, 0x00000003 }, /* POINTER_REGS */ \
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index da7430f1fd88566c4f017a1b491f8de7dce724e8..f4ff300b883ce832335a4915b22bcbfefe64d9ae 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -5357,8 +5357,8 @@ aarch64_expand_prologue (void)
aarch64_emit_probe_stack_range (get_stack_check_protect (), frame_size);
}
- rtx ip0_rtx = gen_rtx_REG (Pmode, IP0_REGNUM);
- rtx ip1_rtx = gen_rtx_REG (Pmode, IP1_REGNUM);
+ rtx tmp0_rtx = gen_rtx_REG (Pmode, EP0_REGNUM);
+ rtx tmp1_rtx = gen_rtx_REG (Pmode, EP1_REGNUM);
/* In theory we should never have both an initial adjustment
and a callee save adjustment. Verify that is the case since the
@@ -5368,7 +5368,7 @@ aarch64_expand_prologue (void)
/* Will only probe if the initial adjustment is larger than the guard
less the amount of the guard reserved for use by the caller's
outgoing args. */
- aarch64_allocate_and_probe_stack_space (ip0_rtx, ip1_rtx, initial_adjust,
+ aarch64_allocate_and_probe_stack_space (tmp0_rtx, tmp1_rtx, initial_adjust,
true, false);
if (callee_adjust != 0)
@@ -5386,7 +5386,7 @@ aarch64_expand_prologue (void)
}
aarch64_add_offset (Pmode, hard_frame_pointer_rtx,
stack_pointer_rtx, callee_offset,
- ip1_rtx, ip0_rtx, frame_pointer_needed);
+ tmp1_rtx, tmp0_rtx, frame_pointer_needed);
if (frame_pointer_needed && !frame_size.is_constant ())
{
/* Variable-sized frames need to describe the save slot
@@ -5428,7 +5428,7 @@ aarch64_expand_prologue (void)
/* We may need to probe the final adjustment if it is larger than the guard
that is assumed by the called. */
- aarch64_allocate_and_probe_stack_space (ip1_rtx, ip0_rtx, final_adjust,
+ aarch64_allocate_and_probe_stack_space (tmp1_rtx, tmp0_rtx, final_adjust,
!frame_pointer_needed, true);
}
@@ -5466,8 +5466,8 @@ aarch64_expand_epilogue (bool for_sibcall)
unsigned reg2 = cfun->machine->frame.wb_candidate2;
rtx cfi_ops = NULL;
rtx_insn *insn;
- /* A stack clash protection prologue may not have left IP0_REGNUM or
- IP1_REGNUM in a usable state. The same is true for allocations
+ /* A stack clash protection prologue may not have left EP0_REGNUM or
+ EP1_REGNUM in a usable state. The same is true for allocations
with an SVE component, since we then need both temporary registers
for each allocation. For stack clash we are in a usable state if
the adjustment is less than GUARD_SIZE - GUARD_USED_BY_CALLER. */
@@ -5501,20 +5501,20 @@ aarch64_expand_epilogue (bool for_sibcall)
/* Restore the stack pointer from the frame pointer if it may not
be the same as the stack pointer. */
- rtx ip0_rtx = gen_rtx_REG (Pmode, IP0_REGNUM);
- rtx ip1_rtx = gen_rtx_REG (Pmode, IP1_REGNUM);
+ rtx tmp0_rtx = gen_rtx_REG (Pmode, EP0_REGNUM);
+ rtx tmp1_rtx = gen_rtx_REG (Pmode, EP1_REGNUM);
if (frame_pointer_needed
&& (maybe_ne (final_adjust, 0) || cfun->calls_alloca))
/* If writeback is used when restoring callee-saves, the CFA
is restored on the instruction doing the writeback. */
aarch64_add_offset (Pmode, stack_pointer_rtx,
hard_frame_pointer_rtx, -callee_offset,
- ip1_rtx, ip0_rtx, callee_adjust == 0);
+ tmp1_rtx, tmp0_rtx, callee_adjust == 0);
else
/* The case where we need to re-use the register here is very rare, so
avoid the complicated condition and just always emit a move if the
immediate doesn't fit. */
- aarch64_add_sp (ip1_rtx, ip0_rtx, final_adjust, true);
+ aarch64_add_sp (tmp1_rtx, tmp0_rtx, final_adjust, true);
aarch64_restore_callee_saves (DImode, callee_offset, R0_REGNUM, R30_REGNUM,
callee_adjust != 0, &cfi_ops);
@@ -5537,8 +5537,11 @@ aarch64_expand_epilogue (bool for_sibcall)
cfi_ops = NULL;
}
- aarch64_add_sp (ip0_rtx, ip1_rtx, initial_adjust,
- !can_inherit_p || df_regs_ever_live_p (IP0_REGNUM));
+ /* Liveness of EP0_REGNUM can not be trusted across function calls either, so
+ add restriction on emit_move optimization to leaf functions. */
+ aarch64_add_sp (tmp0_rtx, tmp1_rtx, initial_adjust,
+ (!can_inherit_p || !crtl->is_leaf
+ || df_regs_ever_live_p (EP0_REGNUM)));
if (cfi_ops)
{
@@ -5654,8 +5657,8 @@ aarch64_output_mi_thunk (FILE *file, tree thunk ATTRIBUTE_UNUSED,
emit_note (NOTE_INSN_PROLOGUE_END);
this_rtx = gen_rtx_REG (Pmode, this_regno);
- temp0 = gen_rtx_REG (Pmode, IP0_REGNUM);
- temp1 = gen_rtx_REG (Pmode, IP1_REGNUM);
+ temp0 = gen_rtx_REG (Pmode, EP0_REGNUM);
+ temp1 = gen_rtx_REG (Pmode, EP1_REGNUM);
if (vcall_offset == 0)
aarch64_add_offset (Pmode, this_rtx, this_rtx, delta, temp1, temp0, false);
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 97bf0a97f09393cb0d8db211eff8952f33b6a66e..3ca6d61e7e28b780f94bf5080b126dac60fe0524 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -35,6 +35,9 @@
(R11_REGNUM 11)
(R12_REGNUM 12)
(R13_REGNUM 13)
+ ;; Scratch registers for prologue/epilogue use.
+ (EP0_REGNUM 12)
+ (EP1_REGNUM 13)
(R14_REGNUM 14)
(R15_REGNUM 15)
(R16_REGNUM 16)
diff --git a/gcc/testsuite/gcc.target/aarch64/test_frame_17.c b/gcc/testsuite/gcc.target/aarch64/test_frame_17.c
index c214431999b60cce8a75204876a8c73ec6304128..44f132911286779f63db60157987d568d3c13d0d 100644
--- a/gcc/testsuite/gcc.target/aarch64/test_frame_17.c
+++ b/gcc/testsuite/gcc.target/aarch64/test_frame_17.c
@@ -1,16 +1,27 @@
/* { dg-do compile } */
-/* { dg-options "-O2 --save-temps" } */
+/* { dg-options "-O2" } */
/* Test reuse of stack adjustment temporaries. */
void foo ();
+/* Should only use 1 mov and re-use it. */
int reuse_mov (int i)
{
int arr[1025];
return arr[i];
}
+/* Should use 2 movs because x12 is live. */
+int no_reuse_mov_live (int i)
+{
+ int arr[1025];
+ register long long a __asm("x12");
+ a = a+1;
+ return arr[i] + a;
+}
+
+/* Should use 2 movs because its not a leaf function. */
int no_reuse_mov (int i)
{
int arr[1025];
@@ -18,4 +29,4 @@ int no_reuse_mov (int i)
return arr[i];
}
-/* { dg-final { scan-assembler-times "mov\tx16, \[0-9\]+" 3 } } */
+/* { dg-final { scan-assembler-times "mov\tx12, \[0-9\]+" 5 } } */
