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goodbyte
January 27, 2007 12:06 AM PST
Problems with inlining array constructors
I am having some performance issues with constructors for array elements, and wonder if there is any easy fix I've missed. I have made following test case:

#include <xmmintrin.h>

union sse_t {
  __m128 ps;
  float f;

  inline sse_t() {}
  inline sse_t(__m128 x): ps(x) {}
};

struct sse_soa_t {
#if 1
  sse_t t[3];
#else
  sse_t a, b, c;
#endif // 0
};


int main(int argc, const char *argp) {
  sse_soa_t x;
  return 0;
}


When compiled with -O2 -ip -ipo on a P4 with icpcbin (ICC) 9.1 20061103 I can see a call to __cxa_vec_ctor in the assembly output, but if "#if 1" is changed to "#if 0" all references to sse_soa_t is optimized out. __cxa_vec_ctor invokes the sse_t::sse_t() constructor through a function pointer, and this kills performance in my application. Is there any easy way around this?
Jennifer Jiang (Intel)
Total Points: 5930
Status Points: 5430
Brown Belt
January 31, 2007 5:31 PM PST
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#1

We're aware of this issue. It's been worked on. Right now there's no work around yet.

If you'd like to be notified on when the fix will be available for this issue, please file a ticket at https://premier.intel.com.

Thanks,

Jennifer

magnus@nuedge.net
June 22, 2008 2:16 PM PDT
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#2 Reply to #1
Hi there. I am experiencing the exact same problem (at least with the Mac version of ICC). I was quite taken by surprise when I discovered that, in the application I am developing, almost 40% of the CPU load is spent constructing arrays with objects that have empty constructors.

Any idea when this will be fixed?

Until it is fixed, I guess I will need to write some ugly workaround (like allocating a char array of sufficient size and cast to the object-array pointer).

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