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Don't document exactly how virtual registers are represented as integers. Code 

shouldn't depend directly on that.

Give an example of how to iterate over all virtual registers in a function
without depending on the representation.

llvm-svn: 123099
This commit is contained in:
Jakob Stoklund Olesen 2011-01-08 23:10:59 +00:00
parent 28d76692b6
commit d3438eb27d
1 changed files with 18 additions and 11 deletions
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29
llvm/docs/CodeGenerator.html
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@ -1559,18 +1559,25 @@ bool RegMapping_Fer::compatible_class(MachineFunction &mf,
</p> </p>
<p>Virtual registers are also denoted by integer numbers. Contrary to physical <p>Virtual registers are also denoted by integer numbers. Contrary to physical
registers, different virtual registers never share the same number. The registers, different virtual registers never share the same number. Whereas
smallest virtual register is normally assigned the number 1024. This may physical registers are statically defined in a <tt>TargetRegisterInfo.td</tt>
change, so, in order to know which is the first virtual register, you should file and cannot be created by the application developer, that is not the case
access <tt>TargetRegisterInfo::FirstVirtualRegister</tt>. Any register whose with virtual registers. In order to create new virtual registers, use the
number is greater than or equal
to <tt>TargetRegisterInfo::FirstVirtualRegister</tt> is considered a virtual
register. Whereas physical registers are statically defined in
a <tt>TargetRegisterInfo.td</tt> file and cannot be created by the
application developer, that is not the case with virtual registers. In order
to create new virtual registers, use the
method <tt>MachineRegisterInfo::createVirtualRegister()</tt>. This method method <tt>MachineRegisterInfo::createVirtualRegister()</tt>. This method
will return a virtual register with the highest code.</p> will return a new virtual register. Use an <tt>IndexedMap&lt;Foo,
VirtReg2IndexFunctor&gt;</tt> to hold information per virtual register. If you
need to enumerate all virtual registers, use the function
<tt>TargetRegisterInfo::index2VirtReg()</tt> to find the virtual register
numbers:</p>
<div class="doc_code">
<pre>
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned VirtReg = TargetRegisterInfo::index2VirtReg(i);
stuff(VirtReg);
}
</pre>
</div>
<p>Before register allocation, the operands of an instruction are mostly virtual <p>Before register allocation, the operands of an instruction are mostly virtual
registers, although physical registers may also be used. In order to check if registers, although physical registers may also be used. In order to check if