The following instruction doesn't compile:
%i = load i32* %p
It throws an error:
test.ll:27:20: error: expected comma after load's type
%i = load i32* %p
^
1 error generated.
How do I fix this?
The syntax of the load instruction was changed in LLVM 3.7. You now need to pass the type of the loaded value, like so:
%i = load i32, i32* %p
Related
%pointer = alloca void (i32)*, align 8
How to check if %pointer is a function pointer?Can I get the parameter list of the function pointer?
Let Create a function that check if an Alloca Instruction Type is a function pointer.
bool isFunctionPointerType(Type *type){
// Check the type here
if(PointerType *pointerType=dyn_cast<PointerType>(type)){
return isFunctionPointerType(pointerType->getElementType());
}
//Exit Condition
else if(type->isFunctionTy()){
return true;
}
return false;
}
In your runOnModule/runOnFunction Pass
if(AllocaInst *allocaInst=dyn_cast<AllocaInst>(inst)){
if(isFunctionPointerType(allocaInst->getType())){
errs()<<"Funtion Pointer Type\n";
}
}
The above pass are tested on the following source.c code
#include <stdio.h>
void fun(int a)
{
printf("Value of a is %d\n", a);
}
int main()
{
void (*fun_ptr)(int) = &fun;
(*fun_ptr)(10);
return 0;
}
Corresponding LLVM Bitcode without any optimization
entry:
%retval = alloca i32, align 4
%fun_ptr = alloca void (i32)*, align 8
store i32 0, i32* %retval, align 4
call void #llvm.dbg.declare(metadata void (i32)** %fun_ptr, metadata !11,
... metadata !15), !dbg !16
store void (i32)* #_Z3funi, void (i32)** %fun_ptr, align 8, !dbg !16
%0 = load void (i32)*, void (i32)** %fun_ptr, align 8, !dbg !17
call void %0(i32 10), !dbg !18
ret i32 0, !dbg !19
Successfully detect func_ptr as a function pointer.
Note that the code use recursion to find the type recursively
Another way is to track the used of func_ptr using def-use chain in LLVM, ie by tracking the StoreInst and check if the source operand is a pointer to function : haven't try yet.
Hope this helps...
If it help please mark it as correct solution or upvote.. Thanks..
im trying to make an llvm backend and i dont know what i need to fix this error
LLVM ERROR: Cannot select: t5: ch = store<ST4[%retval]> t0, Constant:i32<0>, FrameIndex:i64<0>, undef:i64
this is the ir im trying to process
define i32 #main() #0 {
%retval = alloca i32, align 4
store i32 0, i32* %retval, align 4
ret i32 0
}
but i don't know what dag pattern i need to be able to match it.
a tablegen file that contains some of the instructions my arch supports is here https://github.com/jfmherokiller/customllvm/blob/master/llvm/lib/Target/ZCPU/zcpuInstr.td
i just figured out the issue i was looking at the issue wrong
store<ST4[%retval]> t0, Constant:i32<0>, FrameIndex:i64<0>, undef:i64
can be expessed in function form as store(Constant:i32<0>,FrameIndex:i64<0>) or store constant i32 0 in
stack frame index 0.
The information i wasnt getting was that FrameIndex:i64<0> directly related to this line in TargetSelectionDAG.td def frameindex :SDNode<"ISD::FrameIndex",SDTPtrLeaf, [],"FrameIndexSDNode">;
so FrameIndex = frameindex
I've written a very simple llvm IR code. However when I try to run it through llc, I get the following error:
llc: add_test.ll:10:16: error: expected value token
%r = load i32, i32* %retval
^
Here is the code:
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; Function Attrs: nounwind uwtable
define i32 #main() #0 {
entry:
%retval = alloca i32, align 4
store i32 0, i32* %retval
%r = load i32, i32* %retval
ret i32 0
}
attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.ident = !{!0}
!0 = metadata !{metadata !"clang version 3.5.0 "}
The command that i'm running is llc add-test.ll
Does anybody know what could be the problem?
The syntax for load (among others) was changed in LLVM version 3.7. The syntax you're using is the new one. Since you're using version 3.5, you need to use the old syntax, which is:
%r = load i32* %retval
In other words you only specify the type of the parameter, not of the result.
I assume the problem occurred because you're using the current version of the documentation while using an old version of LLVM. The documentation for LLVM 3.5.0 can be found here.
I noticed that llvm.read_register() could read the value of stack pointer, as well as llvm.write_register() could set the value of stack pointer. I add main function to the stackpointer.ll which could be found in the llvm src:
;stackpointer.ll
define i32 #get_stack() nounwind {
%sp = call i32 #llvm.read_register.i32(metadata !0)
ret i32 %sp
}
declare i32 #llvm.read_register.i32(metadata) nounwind
!0 = metadata !{metadata !"sp\00"}
define i32 #main() {
%1 = call i32 #get_stack()
ret i32 %1
}
I tested on an armv7 board running ubuntu 11.04:
lli stackpointer.ll
then, I get a stack dump:
ARMCodeEmitter::emitPseudoInstruction
UNREACHABLE executed at ARMCodeEmitter.cpp:847!
Stack dump:
0. Program arguments: lli stackpointer.ll
1. Running pass 'ARM Machine Code Emitter' on function '#main'
Aborted
I also tried llc:
llc stackpointer.ll -o stackpointer.s
The error messege:
Can't get register for value!
UNREACHABLE executed at ARMCodeEmitter.cpp:1183!
Stack dump:
0. Program arguments: llc stackpointer.ll -o stackpointer.s
1. Running pass 'Function Pass Manager' on moulude 'stackpointer.ll'
2. Running pass 'ARM Instruction Selection' on function '#get_stack'
Aborted
I also tried on x86-64 platform, it didn't work. What is the correct way to use these intrinsics?
My lli didn't like your metadata definition.
I cnagned your
!0 = metadata !{metadata !"sp\00"}
to
!0 = !{!"sp\00"}
And it worked. (Well, since I'm on x86-64, I have also changed everywhere i32 to i64 and sp to rsp).
Plus there were bad whitespace symbols in your formatting, but I think it might be due to StackOverflow/html or something).
I'm new to LLVM IR and I'm implementing PL0 language. http://en.wikipedia.org/wiki/PL/0
I'm generating the testfile as following:
const a = 10;
var b, c;
procedure check1;
var dd;
procedure check2;
c := 2;
begin
dd := 1
end;
begin
b := -1024+53*(-514-766)/93+100;
c := b
end.
And the LLVM IR I generated is like this:
; ModuleID = 'LLVM Module'
define void #__global_main_entry__() {
BlockUnitEntry:
%b = alloca i32
%c = alloca i32
store i32 -1653, i32* %b
%b1 = load i32* %b
store i32 %b1, i32* %c
ret void
}
define void #check1() {
ProcedureEntry:
%dd = alloca i32
store i32 1, i32* %dd
ret void
}
define void #check2() {
ProcedureEntry:
store i32 2, i32* %c
ret void
}
I got a painful error here (at destruction):
While deleting: i32* %c
Use still stuck around after Def is destroyed: store i32 2, i32* %c
test004_llvm_generate: /files/Install/LLVM_Framework/llvm/lib/IR/Value.cpp:79: virtual llvm::Value::~Value(): Assertion `use_empty() && "Uses remain when a value is destroyed!"' failed.
I guess that using variable c(defined in __global_main_entry__) in procedure check2 adds a ref in llvm::Value, when destructing __global_main_entry__ the ref at check2 is causing the error.
I do not know how to solve the problem, and if you have time to be specific, please~
(Moreover, except for the official documentation of llvm. Are there any more resources on LLVM? I found that most tutorials are outdated.)
My full list of code is here: https://github.com/adamcavendish/PL0Compiler
Thanks in advance.
Your IR is malformed - you cannot refer to an instruction from the body of a function different from the one in which the instruction appears, so referring to %c in #check2 is illegal. The failure just happened to occur during module destruction, but it can occur in other circumstances as well.
In general, I recommend running opt -verify on your IR if you're not sure it's legal, it will give you nice error messages. My Eclipse plugin might also help if you want to experiment with IR to see when it is and isn't legal.
As for a solution, it looks like you should create a global variable to represent c, not an instruction. Then you can store into it and load from it in every function in the module.