66 lines
2.3 KiB
ArmAsm
66 lines
2.3 KiB
ArmAsm
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/* libs/opengles/fixed_asm.S
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**
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** Copyright 2006, 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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.text
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.align
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.global gglFloatToFixed
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.global gglFloatToFixedFast
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/*
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* Converts a float to a s15.16 fixed-point number.
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* this doesn't handle floats out of the [-32768, +32768[ range
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* and doesn't performs round-to-nearest.
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* however, it's very fast :-)
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*/
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gglFloatToFixedFast:
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movs r1, r0, lsl #1 /* remove bit sign */
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mov r2, #0x8E /* 127 + 15 */
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sub r1, r2, r1, lsr #24 /* compute shift */
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mov r2, r0, lsl #8 /* mantissa<<8 */
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orr r2, r2, #0x80000000 /* add the missing 1 */
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mov r0, r2, lsr r1 /* scale to 16.16 */
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rsbcs r0, r0, #0 /* negate if needed */
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bx lr
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/*
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* this version rounds-to-nearest and saturates numbers
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* outside the range (but not NaNs).
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*/
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gglFloatToFixed:
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mov r1, r0, lsl #1 /* remove bit sign */
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mov r2, #0x8E /* 127 + 15 */
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subs r1, r2, r1, lsr #24 /* compute shift */
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bls 0f /* too big */
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mov r2, r0, lsl #8 /* mantissa<<8 */
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orr r2, r2, #0x80000000 /* add the missing 1 */
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mov r3, r0
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movs r0, r2, lsr r1 /* scale to 16.16 */
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addcs r0, r0, #1 /* round-to-nearest */
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tst r3, #0x80000000 /* negative? */
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rsbne r0, r0, #0 /* negate if needed */
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bx lr
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0: ands r0, r0, #0x80000000 /* keep only the sign bit */
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moveq r0, #0x7fffffff /* positive, maximum value */
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bx lr
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