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Quentin Carbonneaux 2016-11-09 22:34:05 -05:00
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@ -761,7 +761,7 @@ will be correctly compiled by QBE.
@end
ret %s
Now, if you want to know what a phi instruction is and how
Now, if you want to know what phi instructions are and how
to use them in QBE, you can read the following.
Phi instructions are specific to SSA form. In SSA form
@ -791,10 +791,10 @@ translate it in SSA form is to insert a phi instruction.
%y =w phi @ift 1, @iff 2
ret %y
The phi in the example expresses a choice depending on
which block the control came from. When the `@ift` block
is taken, the phi instruction defining `%y` selects 1;
if `@iff` is taken, 2 is selected.
Phi instructions return one of their arguments depending
on where the control came from. In the example, `%y` is
set to 1 if the `@ift` branch is taken, and it is set to
2 otherwise.
An important remark about phi instructions is that QBE
assumes that if a variable is defined by a phi it respects