common_entry_exit_abi1.S
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//===----------------------Hexagon builtin routine ------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// Functions that implement common sequences in function prologues and epilogues
// used to save code size
.macro FUNCTION_BEGIN name
.text
.globl \name
.type \name, @function
.falign
\name:
.endm
.macro FUNCTION_END name
.size \name, . - \name
.endm
.macro FALLTHROUGH_TAIL_CALL name0 name1
.size \name0, . - \name0
.globl \name1
.type \name1, @function
.falign
\name1:
.endm
// Save r25:24 at fp+#-8 and r27:26 at fp+#-16.
// The compiler knows that the __save_* functions clobber LR. No other
// registers should be used without informing the compiler.
// Since we can only issue one store per packet, we don't hurt performance by
// simply jumping to the right point in this sequence of stores.
FUNCTION_BEGIN __save_r24_through_r27
memd(fp+#-16) = r27:26
FALLTHROUGH_TAIL_CALL __save_r24_through_r27 __save_r24_through_r25
{
memd(fp+#-8) = r25:24
jumpr lr
}
FUNCTION_END __save_r24_through_r25
// For each of the *_before_tailcall functions, jumpr lr is executed in parallel
// with deallocframe. That way, the return gets the old value of lr, which is
// where these functions need to return, and at the same time, lr gets the value
// it needs going into the tail call.
FUNCTION_BEGIN __restore_r24_through_r27_and_deallocframe_before_tailcall
r27:26 = memd(fp+#-16)
FALLTHROUGH_TAIL_CALL __restore_r24_through_r27_and_deallocframe_before_tailcall __restore_r24_through_r25_and_deallocframe_before_tailcall
{
r25:24 = memd(fp+#-8)
deallocframe
jumpr lr
}
FUNCTION_END __restore_r24_through_r25_and_deallocframe_before_tailcall
// Here we use the extra load bandwidth to restore LR early, allowing the return
// to occur in parallel with the deallocframe.
FUNCTION_BEGIN __restore_r24_through_r27_and_deallocframe
{
lr = memw(fp+#4)
r27:26 = memd(fp+#-16)
}
{
r25:24 = memd(fp+#-8)
deallocframe
jumpr lr
}
FUNCTION_END __restore_r24_through_r27_and_deallocframe
// Here the load bandwidth is maximized.
FUNCTION_BEGIN __restore_r24_through_r25_and_deallocframe
{
r25:24 = memd(fp+#-8)
deallocframe
}
jumpr lr
FUNCTION_END __restore_r24_through_r25_and_deallocframe