The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 1 | /* libs/opengles/fixed_asm.S |
| 2 | ** |
| 3 | ** Copyright 2006, The Android Open Source Project |
| 4 | ** |
| 5 | ** Licensed under the Apache License, Version 2.0 (the "License"); |
| 6 | ** you may not use this file except in compliance with the License. |
| 7 | ** You may obtain a copy of the License at |
| 8 | ** |
| 9 | ** http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | ** |
| 11 | ** Unless required by applicable law or agreed to in writing, software |
| 12 | ** distributed under the License is distributed on an "AS IS" BASIS, |
| 13 | ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 14 | ** See the License for the specific language governing permissions and |
| 15 | ** limitations under the License. |
| 16 | */ |
| 17 | |
| 18 | |
| 19 | .text |
| 20 | .align |
| 21 | |
| 22 | .global gglFloatToFixed |
| 23 | .global gglFloatToFixedFast |
| 24 | |
| 25 | |
| 26 | /* |
| 27 | * Converts a float to a s15.16 fixed-point number. |
| 28 | * this doesn't handle floats out of the [-32768, +32768[ range |
| 29 | * and doesn't performs round-to-nearest. |
| 30 | * however, it's very fast :-) |
| 31 | */ |
| 32 | |
| 33 | gglFloatToFixedFast: |
| 34 | movs r1, r0, lsl #1 /* remove bit sign */ |
| 35 | mov r2, #0x8E /* 127 + 15 */ |
| 36 | sub r1, r2, r1, lsr #24 /* compute shift */ |
| 37 | mov r2, r0, lsl #8 /* mantissa<<8 */ |
| 38 | orr r2, r2, #0x80000000 /* add the missing 1 */ |
| 39 | mov r0, r2, lsr r1 /* scale to 16.16 */ |
| 40 | rsbcs r0, r0, #0 /* negate if needed */ |
| 41 | bx lr |
| 42 | |
| 43 | /* |
| 44 | * this version rounds-to-nearest and saturates numbers |
| 45 | * outside the range (but not NaNs). |
| 46 | */ |
| 47 | |
| 48 | gglFloatToFixed: |
| 49 | mov r1, r0, lsl #1 /* remove bit sign */ |
| 50 | mov r2, #0x8E /* 127 + 15 */ |
| 51 | subs r1, r2, r1, lsr #24 /* compute shift */ |
| 52 | bls 0f /* too big */ |
| 53 | mov r2, r0, lsl #8 /* mantissa<<8 */ |
| 54 | orr r2, r2, #0x80000000 /* add the missing 1 */ |
| 55 | mov r3, r0 |
| 56 | movs r0, r2, lsr r1 /* scale to 16.16 */ |
| 57 | addcs r0, r0, #1 /* round-to-nearest */ |
| 58 | tst r3, #0x80000000 /* negative? */ |
| 59 | rsbne r0, r0, #0 /* negate if needed */ |
| 60 | bx lr |
| 61 | |
| 62 | 0: ands r0, r0, #0x80000000 /* keep only the sign bit */ |
| 63 | moveq r0, #0x7fffffff /* positive, maximum value */ |
| 64 | bx lr |
| 65 | |