[LLVMdev] More info, was Help needed after hiatus

[Richard Pennington]

Hi,

I know my last question was very vague (i.e. "It stopped working, what 
went wrong?"), so here is a little more concrete example:

If I run the optimizer (opt) on this code snippet with -std-compile-opts 
the optimizer hangs.


; ModuleID = 'test.ubc'
target datalayout = 
"e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-s0:0:64-f80:32:32"
target triple = "i686-pc-linux-gnu"

declare void @BZALLOC(i32)

define void @f(i32) {
entry:
         %blockSize100k = alloca i32             ; <i32*> [#uses=2]
         store i32 %0, i32* %blockSize100k
         %n = alloca i32         ; <i32*> [#uses=2]
         load i32* %blockSize100k                ; <i32>:1 [#uses=1]
         store i32 %1, i32* %n
         load i32* %n            ; <i32>:2 [#uses=1]
         add i32 %2, 2           ; <i32>:3 [#uses=1]
         mul i32 %3, ptrtoint (i32* getelementptr (i32* null, i32 1) to 
i32)             ; <i32>:4 [#uses=1]
         call void @BZALLOC( i32 %4 )
         br label %return

return:         ; preds = %entry
         ret void
}

This is generated from this test program:

extern void BZALLOC(int s);
void f(int blockSize100k)
{
     int n = blockSize100k;
     BZALLOC( (n+2) * sizeof(unsigned int) );
}

Besides the optimizer hanging, the strange thing about this is that it 
doesn't hang if the blockSize100k variable is a local rather than a 
parameter or if the n+2 is changed to n+1 (!?!).

Is this code intrinsically incorrect, especially the getelementptr for 
sizeof(), or should I look at the optimizer? It seems to be hanging in 
the createInstructionCombiningPass.

-Rich