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8338197: ubsan: ad_x86.hpp:6417:11: runtime error: shift exponent 100 is too large for 32-bit type 'unsigned int' #26890

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8338197: ubsan: ad_x86.hpp:6417:11: runtime error: shift exponent 100 is too large for 32-bit type 'unsigned int' #26890

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8338197: ubsan: ad_x86.hpp:6417:11: runtime error: shift exponent 100…
bulasevich Aug 22, 2025
389a9da
remove redundant code
bulasevich Aug 22, 2025
e3ac870
use uint32_t for _mask
bulasevich Aug 25, 2025
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6 changes: 3 additions & 3 deletions src/hotspot/share/adlc/output_h.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -770,7 +770,8 @@ void ArchDesc::declare_pipe_classes(FILE *fp_hpp) {
fprintf(fp_hpp, " return ((_mask & in2._mask) != 0);\n");
fprintf(fp_hpp, " }\n\n");
fprintf(fp_hpp, " Pipeline_Use_Cycle_Mask& operator<<=(int n) {\n");
fprintf(fp_hpp, " _mask <<= n;\n");
fprintf(fp_hpp, " int max_shift = 8 * sizeof(_mask) - 1;\n");
fprintf(fp_hpp, " _mask <<= (n < max_shift) ? n : max_shift;\n");
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sizeof(_mask) is know - it is sizeof(uint).
Lines 760-768 should be cleaned: <= 32 checks are redundant because of check at line 758. This is leftover from SPARC code (not clean) removal.

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Good point - I removed the redundant code.

As for sizeof(_mask), shouldn’t it just be max_shift = 31 or _mask <<= (n < 32) ? n : 31;?

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Yes, if sizeof(uint) is 32 bits on all our platforms.

Hmm, may be we should use uint32_t for _mask here. Then we can use 32 and 31 without confusion.

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I mean to use _mask <<= (n < 32) ? n : 31;

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Good! Let me correct both variants then. The resulting code is:

class Pipeline_Use_Cycle_Mask {
protected:
  uint32_t _mask;

public:
  Pipeline_Use_Cycle_Mask() : _mask(0) {}

  Pipeline_Use_Cycle_Mask(uint32_t mask) : _mask(mask) {}

  bool overlaps(const Pipeline_Use_Cycle_Mask &in2) const {
    return ((_mask & in2._mask) != 0);
  }

  Pipeline_Use_Cycle_Mask& operator<<=(int n) {
    _mask <<= (n < 32) ? n : 31;
    return *this;
  }

  void Or(const Pipeline_Use_Cycle_Mask &in2) {
    _mask |= in2._mask;
  }

  friend Pipeline_Use_Cycle_Mask operator&(const Pipeline_Use_Cycle_Mask &, const Pipeline_Use_Cycle_Mask &);
  friend Pipeline_Use_Cycle_Mask operator|(const Pipeline_Use_Cycle_Mask &, const Pipeline_Use_Cycle_Mask &);

  friend class Pipeline_Use;

  friend class Pipeline_Use_Element;

};
// code generated for arm32:

class Pipeline_Use_Cycle_Mask {
protected:
  uint32_t _mask1, _mask2, _mask3;

public:
  Pipeline_Use_Cycle_Mask() : _mask1(0), _mask2(0), _mask3(0) {}

  Pipeline_Use_Cycle_Mask(uint32_t mask1, uint32_t mask2, uint32_t mask3) : _mask1(mask1), _mask2(mask2), _mask3(mask3) {}

  Pipeline_Use_Cycle_Mask intersect(const Pipeline_Use_Cycle_Mask &in2) {
    Pipeline_Use_Cycle_Mask out;
    out._mask1 = _mask1 & in2._mask1;
    out._mask2 = _mask2 & in2._mask2;
    out._mask3 = _mask3 & in2._mask3;
    return out;
  }

  bool overlaps(const Pipeline_Use_Cycle_Mask &in2) const {
    return ((_mask1 & in2._mask1) != 0) || ((_mask2 & in2._mask2) != 0) || ((_mask3 & in2._mask3) != 0);
  }

  Pipeline_Use_Cycle_Mask& operator<<=(int n) {
    if (n >= 32)
      do {
        _mask3 = _mask2; _mask2 = _mask1; _mask1 = 0;
      } while ((n -= 32) >= 32);

    if (n > 0) {
      uint m = 32 - n;
      uint32_t mask = (1 << n) - 1;
      uint32_t temp2 = mask & (_mask1 >> m); _mask1 <<= n;
      uint32_t temp3 = mask & (_mask2 >> m); _mask2 <<= n; _mask2 |= temp2;
      _mask3 <<= n; _mask3 |= temp3;
    }
    return *this;
  }

  void Or(const Pipeline_Use_Cycle_Mask &);

  friend Pipeline_Use_Cycle_Mask operator&(const Pipeline_Use_Cycle_Mask &, const Pipeline_Use_Cycle_Mask &);
  friend Pipeline_Use_Cycle_Mask operator|(const Pipeline_Use_Cycle_Mask &, const Pipeline_Use_Cycle_Mask &);

  friend class Pipeline_Use;

  friend class Pipeline_Use_Element;

};

fprintf(fp_hpp, " return *this;\n");
fprintf(fp_hpp, " }\n\n");
fprintf(fp_hpp, " void Or(const Pipeline_Use_Cycle_Mask &in2) {\n");
Expand Down Expand Up @@ -870,8 +871,7 @@ void ArchDesc::declare_pipe_classes(FILE *fp_hpp) {
fprintf(fp_hpp, " }\n\n");
fprintf(fp_hpp, " void step(uint cycles) {\n");
fprintf(fp_hpp, " _used = 0;\n");
fprintf(fp_hpp, " uint max_shift = 8 * sizeof(_mask) - 1;\n");
fprintf(fp_hpp, " _mask <<= (cycles < max_shift) ? cycles : max_shift;\n");
fprintf(fp_hpp, " _mask <<= cycles;\n");
fprintf(fp_hpp, " }\n\n");
fprintf(fp_hpp, " friend class Pipeline_Use;\n");
fprintf(fp_hpp, "};\n\n");
Expand Down