/*
 * Copyright (C) 2011 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.
 */

/*
 * This file contains mips-specific codegen factory support.
 * It is included by
 *
 *        Codegen-$(TARGET_ARCH_VARIANT).c
 *
 */

namespace art {

void genDebuggerUpdate(CompilationUnit* cUnit, int32_t offset);

/*
 * In the Arm code a it is typical to use the link register
 * to hold the target address.  However, for Mips we must
 * ensure that all branch instructions can be restarted if
 * there is a trap in the shadow.  Allocate a temp register.
 */
int loadHelper(CompilationUnit* cUnit, int offset)
{
    int tReg = oatAllocTemp(cUnit);
    loadWordDisp(cUnit, rSELF, offset, tReg);
    return tReg;
}

void spillCoreRegs(CompilationUnit* cUnit)
{
    if (cUnit->numCoreSpills == 0) {
        return;
    }
    uint32_t mask = cUnit->coreSpillMask;
    int offset = cUnit->numCoreSpills * 4;
    opRegImm(cUnit, kOpSub, rSP, offset);
    for (int reg = 0; mask; mask >>= 1, reg++) {
        if (mask & 0x1) {
            offset -= 4;
            storeWordDisp(cUnit, rSP, offset, reg);
        }
    }
}

void unSpillCoreRegs(CompilationUnit* cUnit)
{
    if (cUnit->numCoreSpills == 0) {
        return;
    }
    uint32_t mask = cUnit->coreSpillMask;
    int offset = cUnit->frameSize;
    for (int reg = 0; mask; mask >>= 1, reg++) {
        if (mask & 0x1) {
            offset -= 4;
            loadWordDisp(cUnit, rSP, offset, reg);
        }
    }
    opRegImm(cUnit, kOpAdd, rSP, cUnit->frameSize);
}

void genEntrySequence(CompilationUnit* cUnit, BasicBlock* bb)
{
    int spillCount = cUnit->numCoreSpills + cUnit->numFPSpills;
    /*
     * On entry, rARG0, rARG1, rARG2 & rARG3 are live.  Let the register
     * allocation mechanism know so it doesn't try to use any of them when
     * expanding the frame or flushing.  This leaves the utility
     * code with a single temp: r12.  This should be enough.
     */
    oatLockTemp(cUnit, rARG0);
    oatLockTemp(cUnit, rARG1);
    oatLockTemp(cUnit, rARG2);
    oatLockTemp(cUnit, rARG3);

    /*
     * We can safely skip the stack overflow check if we're
     * a leaf *and* our frame size < fudge factor.
     */
    bool skipOverflowCheck = ((cUnit->attrs & METHOD_IS_LEAF) &&
                              ((size_t)cUnit->frameSize <
                              Thread::kStackOverflowReservedBytes));
    newLIR0(cUnit, kPseudoMethodEntry);
    int checkReg = oatAllocTemp(cUnit);
    int newSP = oatAllocTemp(cUnit);
    if (!skipOverflowCheck) {
        /* Load stack limit */
        loadWordDisp(cUnit, rSELF,
                     Thread::StackEndOffset().Int32Value(), checkReg);
    }
    /* Spill core callee saves */
    spillCoreRegs(cUnit);
    /* NOTE: promotion of FP regs currently unsupported, thus no FP spill */
    DCHECK_EQ(cUnit->numFPSpills, 0);
    if (!skipOverflowCheck) {
        opRegRegImm(cUnit, kOpSub, newSP, rSP,
                    cUnit->frameSize - (spillCount * 4));
        genRegRegCheck(cUnit, kCondCc, newSP, checkReg, NULL,
                       kThrowStackOverflow);
        opRegCopy(cUnit, rSP, newSP);         // Establish stack
    } else {
        opRegImm(cUnit, kOpSub, rSP,
                 cUnit->frameSize - (spillCount * 4));
    }
    storeBaseDisp(cUnit, rSP, 0, rARG0, kWord);
    flushIns(cUnit);

    if (cUnit->genDebugger) {
        // Refresh update debugger callout
        loadWordDisp(cUnit, rSELF,
                     OFFSETOF_MEMBER(Thread, pUpdateDebuggerFromCode), rSUSPEND);
        genDebuggerUpdate(cUnit, DEBUGGER_METHOD_ENTRY);
    }

    oatFreeTemp(cUnit, rARG0);
    oatFreeTemp(cUnit, rARG1);
    oatFreeTemp(cUnit, rARG2);
    oatFreeTemp(cUnit, rARG3);
}

void genExitSequence(CompilationUnit* cUnit, BasicBlock* bb)
{
    /*
     * In the exit path, rRET0/rRET1 are live - make sure they aren't
     * allocated by the register utilities as temps.
     */
    oatLockTemp(cUnit, rRET0);
    oatLockTemp(cUnit, rRET1);

    newLIR0(cUnit, kPseudoMethodExit);
    /* If we're compiling for the debugger, generate an update callout */
    if (cUnit->genDebugger) {
        genDebuggerUpdate(cUnit, DEBUGGER_METHOD_EXIT);
    }
    unSpillCoreRegs(cUnit);
    opReg(cUnit, kOpBx, r_RA);
}

/*
 * Nop any unconditional branches that go to the next instruction.
 * Note: new redundant branches may be inserted later, and we'll
 * use a check in final instruction assembly to nop those out.
 */
void removeRedundantBranches(CompilationUnit* cUnit)
{
    LIR* thisLIR;

    for (thisLIR = (LIR*) cUnit->firstLIRInsn;
         thisLIR != (LIR*) cUnit->lastLIRInsn;
         thisLIR = NEXT_LIR(thisLIR)) {

        /* Branch to the next instruction */
        if (thisLIR->opcode == kMipsB) {
            LIR* nextLIR = thisLIR;

            while (true) {
                nextLIR = NEXT_LIR(nextLIR);

                /*
                 * Is the branch target the next instruction?
                 */
                if (nextLIR == (LIR*) thisLIR->target) {
                    thisLIR->flags.isNop = true;
                    break;
                }

                /*
                 * Found real useful stuff between the branch and the target.
                 * Need to explicitly check the lastLIRInsn here because it
                 * might be the last real instruction.
                 */
                if (!isPseudoOpcode(nextLIR->opcode) ||
                    (nextLIR = (LIR*) cUnit->lastLIRInsn))
                    break;
            }
        }
    }
}


/* Common initialization routine for an architecture family */
bool oatArchInit()
{
    int i;

    for (i = 0; i < kMipsLast; i++) {
        if (EncodingMap[i].opcode != i) {
            LOG(FATAL) << "Encoding order for " << EncodingMap[i].name <<
               " is wrong: expecting " << i << ", seeing " <<
               (int)EncodingMap[i].opcode;
        }
    }

    return oatArchVariantInit();
}

}  // namespace art