forked from OSchip/llvm-project
Finished instruction replacement section, etc. Need better example for replaceAllUsesWith().
llvm-svn: 3806
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@ -669,8 +669,7 @@ pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb
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</p>
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<li>Insertion into an implicit instruction list
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<p>
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<tt>Instruction</tt> instances that are already in
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<p><tt>Instruction</tt> instances that are already in
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<tt>BasicBlock</tt>s are implicitly associated with an existing
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instruction list: the instruction list of the enclosing basic block.
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Thus, we could have accomplished the same thing as the above code
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@ -695,7 +694,7 @@ Instruction* newInst = new Instruction(..., pi);
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</pre>
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which is much cleaner, especially if you're creating a lot of
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instructions and adding them to <tt>BasicBlock</tt>s.
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</p>
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</p>
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</p>
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</ul>
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@ -718,17 +717,59 @@ For example:<p>
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BB->getInstList().erase(I);
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</pre><p>
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<!--_______________________________________________________________________-->
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</ul><h4><a name="schanges_replacing"><hr size=0>Replacing an
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<tt>Instruction</tt> with another <tt>Value</tt></h4><ul>
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<!-- Value::replaceAllUsesWith
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User::replaceUsesOfWith
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Point out: include/llvm/Transforms/Utils/
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especially BasicBlockUtils.h with:
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ReplaceInstWithValue, ReplaceInstWithInst
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<p><i>Replacing individual instructions</i></p>
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<p>
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Including "<a
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href="/doxygen/BasicBlock_8h-source.html">llvm/Transforms/Utils/BasicBlock.h
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</a>" permits use of two very useful replace functions:
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<tt>ReplaceInstWithValue</tt> and <tt>ReplaceInstWithInst</tt>.
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<ul>
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<li>ReplaceInstWithValue
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<p>This function replaces all uses (within a basic block) of a given
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instruction with a value, and then removes the original instruction.
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The following example illustrates the replacement of the result of a
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particular <tt>AllocaInst</tt> that allocates memory for a single
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integer with an null pointer to an integer.</p>
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<pre>
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AllocaInst* instToReplace = ...;
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ReplaceInstWithValue(*instToReplace->getParent(), instToReplace,
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Constant::getNullValue(PointerType::get(Type::IntTy)));
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</pre>
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<li>ReplaceInstWithInst
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<p>This function replaces a particular instruction with another
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instruction. The following example illustrates the replacement of one
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<tt>AllocaInst</tt> with another.<p>
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<pre>
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AllocaInst* instToReplace = ...;
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ReplaceInstWithInst(*instToReplace->getParent(), instToReplace,
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new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt");
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</pre>
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</ul>
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<p><i>Replacing multiple uses of <tt>User</tt>s and
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<tt>Value</tt>s</i></p>
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You can use <tt>Value::replaceAllUsesWith</tt> and
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<tt>User::replaceUsesOfWith</tt> to change more than one use at a
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time. See the doxygen documentation for the <a
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href="/doxygen/classValue.html">Value Class</a> and <a
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href="/doxygen/classUser.html">User Class</a>, respectively, for more
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information.
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<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
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include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
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ReplaceInstWithValue, ReplaceInstWithInst
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-->
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<!-- *********************************************************************** -->
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@ -1575,6 +1616,6 @@ pointer to the parent Function.
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<a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
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<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
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<!-- hhmts start -->
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Last modified: Tue Sep 17 17:41:54 CDT 2002
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Last modified: Tue Sep 17 22:16:24 CDT 2002
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<!-- hhmts end -->
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</font></body></html>
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