[LLVMdev] Problems accessing structs

[Chris Lattner]

On Tue, 11 May 2004, John Criswell wrote:
> > "Kernel"* "createKernel"()
> > {
> > "myKernelMapInstance" = malloc "myKernelMap"
> > "myKernel" = malloc "Kernel"
> > "myKernelMapPTR" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> > store "myKernelMap"* "myKernelMapInstance", "myKernelMap"** "myKernelMapPTR"
> > "puts_kernelPTRPTRMAP" = getelementptr "Kernel"* "myKernel", long 0, ubyte 0
> > "puts_kernelPTRMAP" = load "myKernelMap"** "puts_kernelPTRPTRMAP"
> > "puts_kernelPTR" = getelementptr "myKernelMap"* "puts_kernelPTRMAP", long 0, ubyte 0
> > store int (sbyte*)* %puts_kernel, int (sbyte*)** "puts_kernelPTR"
> > ret "Kernel"* "myKernel"
>     ^---------------
>     + I'm guessing this line might be the problem.
>     :)
>
>
> The initialization code below is never getting reached, so the getchar()
> function pointer is never initialized.

I agree with John.  If you run your code through the optimizers:

$ llvm-as < t.ll | opt -inline -load-vn -gcse -simplifycfg | llvm-dis

You get the following function:

int %main() {
createKernel.entry:
        %myKernelMapInstance.i = malloc %myKernelMap            ; <%myKernelMap*> [#uses=2]
        %myKernel.i = malloc %Kernel            ; <%Kernel*> [#uses=3]
        %myKernelMapPTR.i = getelementptr %Kernel* %myKernel.i, long 0, uint 0          ; <%myKernelMap**> [#uses=1]
        store %myKernelMap* %myKernelMapInstance.i, %myKernelMap** %myKernelMapPTR.i
        %puts_kernelPTR.i = getelementptr %myKernelMap* %myKernelMapInstance.i, long 0, uint 0          ; <int (sbyte*)**> [#uses=1]
        store int (sbyte*)* %puts_kernel, int (sbyte*)** %puts_kernelPTR.i
        %PTRMAP.i = getelementptr %Kernel* %myKernel.i, long 0, uint 0          ; <%myKernelMap**> [#uses=3]
        %MAP.i = load %myKernelMap** %PTRMAP.i          ; <%myKernelMap*> [#uses=1]
        %puts_kernelPTR.i2 = getelementptr %myKernelMap* %MAP.i, long 0, uint 0         ; <int (sbyte*)**> [#uses=1]
        %tmp.i = load int (sbyte*)** %puts_kernelPTR.i2         ; <int (sbyte*)*> [#uses=1]
        "Hello Kernel.i" = getelementptr [14 x sbyte]* "Hello KernelConst", long 0, long 0              ; <sbyte*> [#uses=1]
        %tmp_result.i = call int %tmp.i( sbyte* "Hello Kernel.i" )              ; <int> [#uses=0]
        %MAP.i4 = load %myKernelMap** %PTRMAP.i         ; <%myKernelMap*> [#uses=1]
        %getchar_kernelPTR.i5 = getelementptr %myKernelMap* %MAP.i4, long 0, uint 1             ; <int ()**> [#uses=1]
        %tmp.i = load int ()** %getchar_kernelPTR.i5            ; <int ()*> [#uses=1]
        %tmp_result.i6 = call int %tmp.i( )             ; <int> [#uses=0]
        %myKernel_MapPTR = load %myKernelMap** %PTRMAP.i                ; <%myKernelMap*> [#uses=1]
        free %myKernelMap* %myKernel_MapPTR
        free %Kernel* %myKernel.i
        ret int 0
}


-Chris

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