LLVM 生成for迴圈

1、生成函式

2、使用phi表示式實現for迴圈

3、本例中，kaleidoscopejit原始碼位於./llvm-8.0.1.src/examples/kaleidoscope/include/kaleidoscopejit.h

phi的概念可參考

本例中，生成的llvm ir如下：

define double @myfor(double %a)

**：

#include

"./llvm-8.0.1.src/examples/kaleidoscope/include/kaleidoscopejit.h"
#include
"llvm/adt/apfloat.h"
#include
"llvm/adt/stlextras.h"
#include
"llvm/ir/basicblock.h"
#include
"llvm/ir/constants.h"
#include
"llvm/ir/derivedtypes.h"
#include
"llvm/ir/function.h"
#include
"llvm/ir/irbuilder.h"
#include
"llvm/ir/llvmcontext.h"
#include
"llvm/ir/legacypassmanager.h"
#include
"llvm/ir/module.h"
#include
"llvm/ir/type.h"
#include
"llvm/ir/verifier.h"
#include
"llvm/support/targetselect.h"
#include
"llvm/target/targetmachine.h"
#include
"llvm/transforms/instcombine/instcombine.h"
#include
"llvm/transforms/scalar.h"
#include
"llvm/transforms/scalar/**n.h"
#include
#include
#include
using
namespace std;
using
namespace llvm;
using
namespace llvm::orc;
//llvm items
static llvmcontext thecontext;
static irbuilder<
>
builder
(thecontext)
;static std::unique_ptr themodule;
//jit
static std::unique_ptr thejit;
/* *double myfor(double a)
* *    return a
*} *
*/int
main()
//this function's basic block
basicblock *bb = basicblock::
create
(thecontext,
"myentry"
, thefunction)
;//create the loop basicblock
basicblock *loopbb = basicblock::
create
(thecontext,
"loop"
, thefunction)
;//exit the block
basicblock *afterbb = basicblock::
create
(thecontext,
"afterloop"
, thefunction)
;    builder.
setinsertpoint
(bb)
;//add goto loopbb  in bb
builder.
createbr
(loopbb)
;//start with loopbb
builder.
setinsertpoint
(loopbb)
;//start with 0
value *startval = constantfp::
get(thecontext,
apfloat
(0.0))
;//step is 1
value *stepval = constantfp::
get(thecontext,
apfloat
(1.0))
;//local variable which name is a
phinode *variable = builder.
createphi
(type::
getdoublety
(thecontext),1
,"i");
//if it's from start block, set variable 0
variable-
>
addincoming
(startval, bb)
;//do the body then do cond
//emit loop body in loopbb
//body: arg_a += 1
value *ret = builder.
createfadd
(innerargs[0]
, constantfp::
get(thecontext,
apfloat
(2.0))
,"a");
//do the cond,if variable >= 2 then break(goto afterbb)
value *nextvar = builder.
createfadd
(stepval, variable,
"nextvar");
//if variable < 10 then goto loopbb or gotot afterbb
value *cond = builder.
createfcmpult
(variable, constantfp::
get(thecontext,
apfloat
(10.0))
,"cmptmp");
builder.
createcondbr
(cond, loopbb, afterbb)
;    builder.
setinsertpoint
(afterbb)
;    variable-
>
addincoming
(nextvar, loopbb)
;    builder.
createret
(ret)
;    thefunction-
>
print
(errs()
);//using jit to run this code
auto h = thejit-
>
addmodule
(std::
move
(themodule));
auto exprsymbol = thejit-
>
findsymbol
("myfor");
double
(*myfor)
(double)=
(double(*
)(double))
(intptr_t)
cantfail
(exprsymbol.
getaddress()
);cout <<
myfor(40
)<}

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