[llvm-bugs] [Bug 27085] New: scalar/vector operations lead to division by zero

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27085

            Bug ID: 27085
           Summary: scalar/vector operations lead to division by zero
           Product: clang
           Version: 3.7
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: regis.portalez at gmail.com
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org
    Classification: Unclassified

try to compile the following code (C) using clang 3.7 (using only mem2reg pass)

typedef unsigned char char4  __attribute__ ((vector_size (4)));

char4 f1 (char4  v)
{
  return v / 2;
}

this compiles down to (+ debug info): 

define <4 x i8> @f1(<4 x i8> %v) {
entry:
  %div = udiv <4 x i8> %v, bitcast (<1 x i32> <i32 2> to <4 x i8>)
  ret <4 x i8> %div
}

according to http://llvm.org/docs/LangRef.html#bitcast-to-instruction, bitcast
instruction does not change any bit, meaning bitcast (<1 x i32> <i32 2> to <4 x
i8>) returns <2, 0, 0, 0> as char vector. 

therefore the division in the original source code generates a division by
zero. 


I would have expected the following IL: 
define <4 x i8> @f1(<4 x i8> %v) {
entry:
  %div = udiv <4 x i8> %v, <4 x i8> <i8 2, i8 2, i8 2, i8 2>
  ret <4 x i8> %div
}

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