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LLL: Implement a switch expression.

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benjaminion 2017-07-22 07:57:38 +01:00 committed by Alex Beregszaszi
parent c61610302a
commit 326c7887a4
1 changed files with 38 additions and 0 deletions
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38
liblll/CodeFragment.cpp
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@ -514,6 +514,44 @@ void CodeFragment::constructOperation(sp::utree const& _t, CompilerState& _s)
m_asm.appendJump(begin);
m_asm << end.tag();
}
else if (us == "SWITCH")
{
requireMinSize(1);
bool hasDefault = (code.size() % 2 == 1);
int startDeposit = m_asm.deposit();
int targetDeposit = hasDefault ? code[code.size() - 1].m_asm.deposit() : 0;
// The conditions
AssemblyItems jumpTags;
for (unsigned i = 0; i < code.size() - 1; i += 2)
{
requireDeposit(i, 1);
m_asm.append(code[i].m_asm);
jumpTags.push_back(m_asm.appendJumpI());
}
// The default, if present
if (hasDefault)
m_asm.append(code[code.size() - 1].m_asm);
// The targets - appending in reverse makes the top case the most efficient.
if (code.size() > 1)
{
auto end = m_asm.appendJump();
for (int i = 2 * (code.size() / 2 - 1); i >= 0; i -= 2)
{
m_asm << jumpTags[i / 2].tag();
requireDeposit(i + 1, targetDeposit);
m_asm.append(code[i + 1].m_asm);
if (i != 0)
m_asm.appendJump(end);
}
m_asm << end.tag();
}
m_asm.setDeposit(startDeposit + targetDeposit);
}
else if (us == "ALLOC")
{
requireSize(1);