<body>
-<div class="doc_title">Kaleidoscope: Extending the Language: Mutable Variables</div>
+<h1>Kaleidoscope: Extending the Language: Mutable Variables</h1>
<ul>
<li><a href="index.html">Up to Tutorial Index</a></li>
</div>
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-<div class="doc_section"><a name="intro">Chapter 7 Introduction</a></div>
+<h2><a name="intro">Chapter 7 Introduction</a></h2>
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-<div class="doc_text">
+<div>
<p>Welcome to Chapter 7 of the "<a href="index.html">Implementing a language
with LLVM</a>" tutorial. In chapters 1 through 6, we've built a very
</div>
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-<div class="doc_section"><a name="why">Why is this a hard problem?</a></div>
+<h2><a name="why">Why is this a hard problem?</a></h2>
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-<div class="doc_text">
+<div>
<p>
To understand why mutable variables cause complexities in SSA construction,
</div>
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-<div class="doc_section"><a name="memory">Memory in LLVM</a></div>
+<h2><a name="memory">Memory in LLVM</a></h2>
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-<div class="doc_text">
+<div>
<p>The 'trick' here is that while LLVM does require all register values to be
in SSA form, it does not require (or permit) memory objects to be in SSA form.
</div>
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-<div class="doc_section"><a name="kalvars">Mutable Variables in
-Kaleidoscope</a></div>
+<h2><a name="kalvars">Mutable Variables in Kaleidoscope</a></h2>
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-<div class="doc_text">
+<div>
<p>Now that we know the sort of problem we want to tackle, lets see what this
looks like in the context of our little Kaleidoscope language. We're going to
</div>
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-<div class="doc_section"><a name="adjustments">Adjusting Existing Variables for
-Mutation</a></div>
+<h2><a name="adjustments">Adjusting Existing Variables for Mutation</a></h2>
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-<div class="doc_text">
+<div>
<p>
The symbol table in Kaleidoscope is managed at code generation time by the
<b>// Reload, increment, and restore the alloca. This handles the case where
// the body of the loop mutates the variable.
Value *CurVar = Builder.CreateLoad(Alloca);
- Value *NextVar = Builder.CreateAdd(CurVar, StepVal, "nextvar");
+ Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
Builder.CreateStore(NextVar, Alloca);</b>
...
</pre>
else: ; preds = %entry
<b>%x3 = load double* %x1</b>
- %subtmp = sub double %x3, 1.000000e+00
- %calltmp = call double @fib( double %subtmp )
+ %subtmp = fsub double %x3, 1.000000e+00
+ %calltmp = call double @fib(double %subtmp)
<b>%x4 = load double* %x1</b>
- %subtmp5 = sub double %x4, 2.000000e+00
- %calltmp6 = call double @fib( double %subtmp5 )
- %addtmp = add double %calltmp, %calltmp6
+ %subtmp5 = fsub double %x4, 2.000000e+00
+ %calltmp6 = call double @fib(double %subtmp5)
+ %addtmp = fadd double %calltmp, %calltmp6
br label %ifcont
ifcont: ; preds = %else, %then
br label %ifcont
else:
- %subtmp = sub double <b>%x</b>, 1.000000e+00
- %calltmp = call double @fib( double %subtmp )
- %subtmp5 = sub double <b>%x</b>, 2.000000e+00
- %calltmp6 = call double @fib( double %subtmp5 )
- %addtmp = add double %calltmp, %calltmp6
+ %subtmp = fsub double <b>%x</b>, 1.000000e+00
+ %calltmp = call double @fib(double %subtmp)
+ %subtmp5 = fsub double <b>%x</b>, 2.000000e+00
+ %calltmp6 = call double @fib(double %subtmp5)
+ %addtmp = fadd double %calltmp, %calltmp6
br label %ifcont
ifcont: ; preds = %else, %then
br i1 %ifcond, label %else, label %ifcont
else:
- %subtmp = sub double %x, 1.000000e+00
- %calltmp = call double @fib( double %subtmp )
- %subtmp5 = sub double %x, 2.000000e+00
- %calltmp6 = call double @fib( double %subtmp5 )
- %addtmp = add double %calltmp, %calltmp6
+ %subtmp = fsub double %x, 1.000000e+00
+ %calltmp = call double @fib(double %subtmp)
+ %subtmp5 = fsub double %x, 2.000000e+00
+ %calltmp6 = call double @fib(double %subtmp5)
+ %addtmp = fadd double %calltmp, %calltmp6
ret double %addtmp
ifcont:
</div>
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-<div class="doc_section"><a name="assignment">New Assignment Operator</a></div>
+<h2><a name="assignment">New Assignment Operator</a></h2>
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-<div class="doc_text">
+<div>
<p>With our current framework, adding a new assignment operator is really
simple. We will parse it just like any other binary operator, but handle it
</div>
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-<div class="doc_section"><a name="localvars">User-defined Local
-Variables</a></div>
+<h2><a name="localvars">User-defined Local Variables</a></h2>
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-<div class="doc_text">
+<div>
<p>Adding var/in is just like any other other extensions we made to
Kaleidoscope: we extend the lexer, the parser, the AST and the code generator.
</div>
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-<div class="doc_section"><a name="code">Full Code Listing</a></div>
+<h2><a name="code">Full Code Listing</a></h2>
<!-- *********************************************************************** -->
-<div class="doc_text">
+<div>
<p>
Here is the complete code listing for our running example, enhanced with mutable
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/Analysis/Verifier.h"
+#include "llvm/Analysis/Passes.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetSelect.h"
#include "llvm/Transforms/Scalar.h"
if (L == 0 || R == 0) return 0;
switch (Op) {
- case '+': return Builder.CreateAdd(L, R, "addtmp");
- case '-': return Builder.CreateSub(L, R, "subtmp");
- case '*': return Builder.CreateMul(L, R, "multmp");
+ case '+': return Builder.CreateFAdd(L, R, "addtmp");
+ case '-': return Builder.CreateFSub(L, R, "subtmp");
+ case '*': return Builder.CreateFMul(L, R, "multmp");
case '<':
L = Builder.CreateFCmpULT(L, R, "cmptmp");
// Convert bool 0/1 to double 0.0 or 1.0
// Emit merge block.
TheFunction->getBasicBlockList().push_back(MergeBB);
Builder.SetInsertPoint(MergeBB);
- PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()),
+ PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
"iftmp");
PN->addIncoming(ThenV, ThenBB);
// Reload, increment, and restore the alloca. This handles the case where
// the body of the loop mutates the variable.
Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
- Value *NextVar = Builder.CreateAdd(CurVar, StepVal, "nextvar");
+ Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
Builder.CreateStore(NextVar, Alloca);
// Convert condition to a bool by comparing equal to 0.0.
// Set up the optimizer pipeline. Start with registering info about how the
// target lays out data structures.
OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData()));
+ // Provide basic AliasAnalysis support for GVN.
+ OurFPM.add(createBasicAliasAnalysisPass());
// Promote allocas to registers.
OurFPM.add(createPromoteMemoryToRegisterPass());
// Do simple "peephole" optimizations and bit-twiddling optzns.
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<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
- <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
+ <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
Last modified: $Date$
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