[llvm-bugs] [Bug 46162] New: [DebugInfo at O2] SLP Vectorizer drops DebugInfo

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46162

            Bug ID: 46162
           Summary: [DebugInfo at O2] SLP Vectorizer drops DebugInfo
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: Wolfgang_Pieb at playstation.sony.com
                CC: llvm-bugs at lists.llvm.org

/* Compile the following source with clang -g -O2. The SLP Vectorizer pass 
   drops location information for the local variables x1 and x2. */

typedef unsigned int U32;
typedef float F32;
extern "C" double log(float);
extern "C" double sqrt(float);

extern unsigned RandU32();

float RandF32()
{
  U32 uRand = RandU32();
  F32 fRand = ((F32)uRand / 4294967810.0f);
  return(fRand);
}

void randGauss(float work[2])
{
  float x1, x2, w;

  do {
    x1 = 2.f * RandF32() - 1.f;
    x2 = 2.f * RandF32() - 1.f;
    w = x1 * x1 + x2 * x2;
  } while ( w >= 1.f );

  w = sqrt( (-2.f * log( w ) ) / w );
  work[0] = x1 * w;
  work[1] = x2 * w;
}

/* This turns out to be a rather special case, where the same operation is
performed on 2 different local variables in a lexical block. The vectorizer
places the 2 variables in 2 different lanes of a vector register and performs
the operation on both simultaneously.
After some investigation I didn't see an obvious way to fix this. The current
compiler infrastructure seems insufficient to describe what's going on. Given
that ist's a corner case I would consider it low priority. */

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