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/*
* Copyright (C) 2008 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Target-specific optimization and run-time hints
*/
#include "Dalvik.h"
#include "libdex/DexClass.h"
#include <stdlib.h>
#include <stddef.h>
#include <sys/stat.h>
/*
* The class loader will associate with each method a 32-bit info word
* (jniArgInfo) to support JNI calls. The high order 4 bits of this word
* are the same for all targets, while the lower 28 are used for hints to
* allow accelerated JNI bridge transfers.
*
* jniArgInfo (32-bit int) layout:
*
* SRRRHHHH HHHHHHHH HHHHHHHH HHHHHHHH
*
* S - if set, ignore the hints and do things the hard way (scan signature)
* R - return-type enumeration
* H - target-specific hints (see below for details)
*
* This function produces arm-specific hints - specifically a description
* of padding required to keep all 64-bit parameters properly aligned.
*
* ARM JNI hint format
*
* LLLL FFFFFFFF FFFFFFFF FFFFFFFF
*
* L - number of double-words of storage required on the stack (0-30 words)
* F - pad flag -- if set, write a pad word to the stack before copying
* the next 32 bits
*
* If there are too many arguments to construct valid hints, this function will
* return a result with the S bit set.
*/
u4 dvmPlatformInvokeHints(const DexProto* proto)
{
const char* sig = dexProtoGetShorty(proto);
int padFlags, jniHints;
char sigByte;
int stackOffset, padMask;
stackOffset = padFlags = 0;
padMask = 0x00000001;
/* Skip past the return type */
sig++;
while (true) {
sigByte = *(sig++);
if (sigByte == '\0')
break;
if (sigByte == 'D' || sigByte == 'J') {
if ((stackOffset & 1) != 0) {
padFlags |= padMask;
stackOffset++;
padMask <<= 1;
}
stackOffset += 2;
padMask <<= 2;
} else {
stackOffset++;
padMask <<= 1;
}
}
jniHints = 0;
if (stackOffset > DALVIK_JNI_COUNT_SHIFT) {
/* too big for "fast" version */
jniHints = DALVIK_JNI_NO_ARG_INFO;
} else {
assert((padFlags & (0xffffffff << DALVIK_JNI_COUNT_SHIFT)) == 0);
stackOffset -= 2; // r2/r3 holds first two items
if (stackOffset < 0)
stackOffset = 0;
jniHints |= ((stackOffset+1) / 2) << DALVIK_JNI_COUNT_SHIFT;
jniHints |= padFlags;
}
return jniHints;
}
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