66 lines
2.4 KiB
ArmAsm
66 lines
2.4 KiB
ArmAsm
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "asm_support_arm.S"
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.section .text
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// These functions are used to check for the CPU's support for the sdiv and
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// ARMv8-A instructions at runtime. They will either return the value 1 or will
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// cause an invalid instruction trap (SIGILL signal), for which the signal handler
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// (bad_instr_handle(), in instruction_set_features_arm.cc) must arrange to set
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// the r0 register to 0 and move the pc forward by 4 bytes (to skip the invalid
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// instruction).
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// Note: For ARM T32, instructions can be either 16b or 32b, but bad_instr_handle()
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// deals only with 32b instructions for now.
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ENTRY artCheckForArmSdivInstruction
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mov r1,#1
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// Depending on the architecture, the assembler will not allow an
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// sdiv instruction, so we will have to output the bytes directly.
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// The T32 encoding for sdiv r0,r1,r1 is two 16bit words: 0xfb91 0xf0f1, with little endianness.
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.byte 0x91,0xfb
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.byte 0xf1,0xf0
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// If the divide worked, r0 will have the value #1 (result of sdiv).
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// It will have 0 otherwise (set by the signal handler)
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// the value is just returned from this function.
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bx lr
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END artCheckForArmSdivInstruction
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ENTRY artCheckForArmv8AInstructions
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// Depending on the architecture, the assembler will not allow a
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// `vrint` instruction, so we will have to output the bytes directly.
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// Move `true` into the result register. The signal handler will set it to 0
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// if execution of the instruction below fails
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mov r0,#1
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// Store S0 in the caller saved R1. If the instruction below succeeds, S0 will
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// be clobbered but it will not be caller saved (ARM still uses soft FP).
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vmov r1, s0
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// The T32 encoding for vrinta.f32.f32 s0,s0 is two 16bit words: 0xfeb8,0x0a40, with little
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// endianness.
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.byte 0xb8,0xfe
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.byte 0x40,0x0a
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// Restore S0 (see above comment).
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vmov s0, r1
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bx lr
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END artCheckForArmv8AInstructions
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