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Simplify the first example, as the LLVM IR interfaces have evolved. Other

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examples in this doc could also be simplified dramatically in similar ways.

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Chris Lattner 2004-08-03 00:17:21 +00:00
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@ -131,31 +131,28 @@ I noted that most of the important LLVM IR (Intermediate Representation) C++
classes were derived from the Value class. The full power of that simple
design only became fully understood once I started constructing executable
expressions for Stacker.</p>
<p>This really makes your programming go faster. Think about compiling code
for the following C/C++ expression: <code>(a|b)*((x+1)/(y+1))</code>. Assuming
the values are on the stack in the order a, b, x, y, this could be
expressed in stacker as: <code>1 + SWAP 1 + / ROT2 OR *</code>.
You could write a function using LLVM that computes this expression like this: </p>
<pre><code>
You could write a function using LLVM that computes this expression like
this: </p>
<div class="doc_code"><pre>
Value*
expression(BasicBlock* bb, Value* a, Value* b, Value* x, Value* y )
{
Instruction* tail = bb->getTerminator();
ConstantSInt* one = ConstantSInt::get( Type::IntTy, 1);
BinaryOperator* or1 =
BinaryOperator::create( Instruction::Or, a, b, "", tail );
BinaryOperator* add1 =
BinaryOperator::create( Instruction::Add, x, one, "", tail );
BinaryOperator* add2 =
BinaryOperator::create( Instruction::Add, y, one, "", tail );
BinaryOperator* div1 =
BinaryOperator::create( Instruction::Div, add1, add2, "", tail);
BinaryOperator* mult1 =
BinaryOperator::create( Instruction::Mul, or1, div1, "", tail );
ConstantSInt* one = ConstantSInt::get(Type::IntTy, 1);
BinaryOperator* or1 = BinaryOperator::createOr(a, b, "", bb);
BinaryOperator* add1 = BinaryOperator::createAdd(x, one, "", bb);
BinaryOperator* add2 = BinaryOperator::createAdd(y, one, "", bb);
BinaryOperator* div1 = BinaryOperator::createDiv(add1, add2, "", bb);
BinaryOperator* mult1 = BinaryOperator::createMul(or1, div1, "", bb);
return mult1;
}
</code></pre>
</pre></div>
<p>"Okay, big deal," you say? It is a big deal. Here's why. Note that I didn't
have to tell this function which kinds of Values are being passed in. They could be
<code>Instruction</code>s, <code>Constant</code>s, <code>GlobalVariable</code>s, or