1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 /* 17 * Target-specific optimization and run-time hints 18 */ 19 20 21 #include "Dalvik.h" 22 #include "libdex/DexClass.h" 23 24 #include <stdlib.h> 25 #include <stddef.h> 26 #include <sys/stat.h> 27 28 29 /* 30 * The class loader will associate with each method a 32-bit info word 31 * (jniArgInfo) to support JNI calls. The high order 4 bits of this word 32 * are the same for all targets, while the lower 28 are used for hints to 33 * allow accelerated JNI bridge transfers. 34 * 35 * jniArgInfo (32-bit int) layout: 36 * 37 * SRRRHHHH HHHHHHHH HHHHHHHH HHHHHHHH 38 * 39 * S - if set, ignore the hints and do things the hard way (scan signature) 40 * R - return-type enumeration 41 * H - target-specific hints (see below for details) 42 * 43 * This function produces arm-specific hints - specifically a description 44 * of padding required to keep all 64-bit parameters properly aligned. 45 * 46 * ARM JNI hint format 47 * 48 * LLLL FFFFFFFF FFFFFFFF FFFFFFFF 49 * 50 * L - number of double-words of storage required on the stack (0-30 words) 51 * F - pad flag -- if set, write a pad word to the stack before copying 52 * the next 32 bits 53 * 54 * If there are too many arguments to construct valid hints, this function will 55 * return a result with the S bit set. 56 */ 57 u4 dvmPlatformInvokeHints(const DexProto* proto) 58 { 59 const char* sig = dexProtoGetShorty(proto); 60 int padFlags, jniHints; 61 char sigByte; 62 int stackOffset, padMask; 63 64 stackOffset = padFlags = 0; 65 padMask = 0x00000001; 66 67 /* Skip past the return type */ 68 sig++; 69 70 while (true) { 71 sigByte = *(sig++); 72 73 if (sigByte == '\0') 74 break; 75 76 if (sigByte == 'D' || sigByte == 'J') { 77 if ((stackOffset & 1) != 0) { 78 padFlags |= padMask; 79 stackOffset++; 80 padMask <<= 1; 81 } 82 stackOffset += 2; 83 padMask <<= 2; 84 } else { 85 stackOffset++; 86 padMask <<= 1; 87 } 88 } 89 90 jniHints = 0; 91 92 if (stackOffset > DALVIK_JNI_COUNT_SHIFT) { 93 /* too big for "fast" version */ 94 jniHints = DALVIK_JNI_NO_ARG_INFO; 95 } else { 96 assert((padFlags & (0xffffffff << DALVIK_JNI_COUNT_SHIFT)) == 0); 97 stackOffset -= 2; // r2/r3 holds first two items 98 if (stackOffset < 0) 99 stackOffset = 0; 100 jniHints |= ((stackOffset+1) / 2) << DALVIK_JNI_COUNT_SHIFT; 101 jniHints |= padFlags; 102 } 103 104 return jniHints; 105 } 106