[LLVMbugs] [Bug 23845] New: Apparent miscompilation with BBVectorize and sqrt

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun Jun 14 08:56:55 PDT 2015


            Bug ID: 23845
           Summary: Apparent miscompilation with BBVectorize and sqrt
           Product: new-bugs
           Version: 3.6
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: nick at indigorenderer.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 14470
  --> https://llvm.org/bugs/attachment.cgi?id=14470&action=edit
unoptimised IR

In the unoptimised IR there are two calls to wombat326, each of which does a
sqrt. (see wobble211)

In the optimised code there is only one sqrt call.
One sqrt call seems to have been erroneously removed.

Disabling BBVectorize seems to remove the miscompilation.

Optimisation passes are basically the standard -03, with vectorisation passes

Platform: LLVM 3.6, windows 64-bit.  Using LLVM for jitting.

Unoptimised IR:

Optimised IR: https://gist.github.com/anonymous/5029a142fcc946d708a8

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