<br><br><div class="gmail_quote">On Thu, Sep 22, 2011 at 3:46 PM, sarath chandra <span dir="ltr"><<a href="mailto:sarathcse19@gmail.com">sarathcse19@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi James,<br><br>First i converted the void * to int* and then did FPToSI...then did SHL...( because CreateShl only accepts integers... i pointer casted it to int64 type first)... Below is the code snippet....<br><br><br>
lhs = mBuilder.CreateStructGEP(firstArg, 0);<br>
lhs = mBuilder.CreateLoad(lhs);<br> lhs = mBuilder.CreatePointerCast(lhs, PointerType::get(<br> mBuilder.getInt64Ty(), 0));<br> int typelhs = getValueType(lhs);<br> rhs = mBuilder.CreateStructGEP(secondArg, 0);<br>
rhs = mBuilder.CreateLoad(rhs);<br> rhs = mBuilder.CreatePointerCast(rhs, PointerType::get(<br> mBuilder.getInt64Ty(), 0));<br><br> lhs = mBuilder.CreateLoad(lhs);<br> rhs = mBuilder.CreateLoad(rhs);<br>
<br> lhs = convertDoubleToInt64(lhs); // used FPToSI<br> rhs = convertDoubleToInt64(rhs);// " "<br><br> //lhs = mBuilder.CreateLoad(lhs);<br> //rhs = mBuilder.CreateLoad(rhs);<br><br> lhs = mBuilder.CreateShl(lhs, rhs);<br>
//lhs = mBuilder.CreatePointerCast(lhs, PointerType::get(mBuilder.getDoubleTy(),0));<br> lhs = convertIntToDouble(lhs);<br> typelhs = getValueType(lhs);<br><br><br><br> llvm::Value* returnValue = mBuilder.CreateAlloca(PointerType::get(<br>
mModule->getTypeByName("Value"), 0));<br><br> llvm::Value* valueStructSize = getValueStructSize();<br> llvm::Value* memory = insertCallToMalloc(valueStructSize);<br><br> memory = mBuilder.CreatePointerCast(memory, PointerType::get(<br>
mModule->getTypeByName("Value"), 0));<br><br> mBuilder.CreateStore(memory, returnValue);<br><br> allocateAndAssignDoubleTypeVar(mBuilder.CreateLoad(returnValue), lhs);<br><br> //return the value<br>
mBuilder.CreateRet(mBuilder.CreateLoad(returnValue));<br><br><br> /*<br> * create call to SHL function<br> */<br> mCurrentFunction = previousFunction;<br> mBuilder.SetInsertPoint(previousBlock);<br><br>
return mBuilder.CreateCall2(shlFunction, aLHS, aRHS);<div><div></div><div class="h5"><br><br><br><div class="gmail_quote">On Thu, Sep 22, 2011 at 3:40 PM, James Molloy <span dir="ltr"><<a href="mailto:James.Molloy@arm.com" target="_blank">James.Molloy@arm.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Sarath,<br>
<br>
Your example will break.<br>
<br>
If the values are held internally as doubles casted to void* (which incidentally will only work on 64-bit systems), just casting void* -> int* will not get you a valid integer value. It will get you the double's internal representation as an integer. For example (actual values are made up):<br>
<br>
double a = 42.0;<br>
void *v = (void*)&a;<br>
int b = *(int*)v;<br>
<br>
"b" will not contain 42. It will contain what looks like random garbage (although it is the IEE754 floating point representation of "42.0").<br>
<br>
You need to perform an actual cast:<br>
<br>
double a = 42.0;<br>
void *v = (void*)&a;<br>
double b = *(double*)v;<br>
int c = (int)b;<br>
<br>
"c" will contain 42.<br>
<br>
In LLVM speak, you need to LOAD as a double*, perform a fptosi to create an int64, perform the shift, then sitofp and store:<br>
<br>
%1 = load bitcast i8* %arg0 to double* ; Cast the void* to double*, then load it.<br>
%2 = load bitcast i8* %arg1 to double*<br>
<br>
%3 = fptosi double %1 to i64 ; Perform explicit double -> int conversion.<br>
%4 = fptosi double %2 to i64<br>
<br>
%5 = shr i64 %3, %4 ; Perform your operation.<br>
<br>
%6 = sitofp i64 %5 to double ; Convert explicitly back to integer representation.<br>
<br>
%7 = store bitcast i8* %dest to double*, double %6 ; Store back, reinterpreting your void* (which is i8* in LLVM) as a double*.<br>
<br>
<br>
Hopefully this makes sense, especially if you know how you would have to do it in C.<br>
<br>
Cheers,<br>
<br>
James<br>
<br>
From: sarath chandra [mailto:<a href="mailto:sarathcse19@gmail.com" target="_blank">sarathcse19@gmail.com</a>]<br>
Sent: 22 September 2011 10:49<br>
To: James Molloy<br>
Subject: Re: [LLVMdev] Need help in converting int to double<br>
<div><div></div><div><br>
Hi James,<br>
<br>
CreateShl() accepts only integers or vectors as arguments. At the starting my arguments , let us suppose LHS,RHS, are double values. To pass them as arguments to CreateShl(), i used Pointer Casting to convert the Void* to Int*. Now the problem is after getting the result is, the result variable which captures the output is Int*.. i wanted to make it Double*..(so that i can accomadate it in value structure)<br>
On Thu, Sep 22, 2011 at 3:12 PM, James Molloy <<a href="mailto:James.Molloy@arm.com" target="_blank">James.Molloy@arm.com</a>> wrote:<br>
Hi Sarath,<br>
<br>
If you can only hold doubles (not integers), and you originally converted the doubles to integers to do an integer shift, why can you not just convert the result back to a double using CreateFPToSI ?<br>
<br>
CreateFPToSI(CreateShr(CreateSIToFP(arg0), CreateSIToFP(arg1)))<br>
<br>
Cheers,<br>
<br>
James<br>
<br>
From: <a href="mailto:llvmdev-bounces@cs.uiuc.edu" target="_blank">llvmdev-bounces@cs.uiuc.edu</a> [mailto:<a href="mailto:llvmdev-bounces@cs.uiuc.edu" target="_blank">llvmdev-bounces@cs.uiuc.edu</a>] On Behalf Of sarath chandra<br>
Sent: 22 September 2011 10:37<br>
To: <a href="mailto:llvmdev@cs.uiuc.edu" target="_blank">llvmdev@cs.uiuc.edu</a><br>
Subject: [LLVMdev] Need help in converting int to double<br>
<br>
Hi,<br>
<br>
I'm pursuing M.Tech course. As a part of the project work i'm using LLVM as back-end. My project area is "Enhancing the performance of V8 javascript engine using LLVM as a back-end".<br>
<br>
Now i'm writing code for shift left(SHL) operator. I had my own Value Structure .. it's like this<br>
<br>
Struct Value<br>
{<br>
void *val ;<br>
char type;<br>
}<br>
<br>
The "char type" holds DoubleType,DoubleConst,StringType,StringConst...<br>
<br>
when i'm executing the IrBuilder.CreateShl(LHS,RHS) instruction it is returning an integer value as output.. i'm unable to store the value in my structure....(because my structure can hold Doubles,Strings).<br>
<br>
Is there any way to store the integer output in my structure( i used CreateSIToFP() to change int to double)........<br>
<br>
Thanks in advance<br>
<br>
Regards,<br>
<br>
(¨`·.·´¨)<br>
`·.¸(¨`·.·´¨)<br>
(¨`·.·´¨)¸.·´ Sarath!!!<br>
`·.¸.·´<br>
<br>
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<br>
<br>
<br>
--<br>
Sairam,<br>
<br>
(¨`·.·´¨)<br>
`·.¸(¨`·.·´¨)<br>
(¨`·.·´¨)¸.·´ Sarath!!!<br>
`·.¸.·´<br>
<br>
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</div></div></blockquote></div><br><br clear="all"><br></div></div><font color="#888888">-- <br>Sairam,<br><br> (¨`·.·´¨) <br> `·.¸(¨`·.·´¨) <br> (¨`·.·´¨)¸.·´ Sarath!!!<br> `·.¸.·´<br>
</font></blockquote></div><br><br clear="all"><br>-- <br>Sairam,<br><br> (¨`·.·´¨) <br> `·.¸(¨`·.·´¨) <br> (¨`·.·´¨)¸.·´ Sarath!!!<br> `·.¸.·´<br>