[LLVMbugs] [Bug 11319] New: ARM instruction selection failure when -promote-elements=true and -mattr=+neon

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun Nov 6 08:45:36 PST 2011


             Bug #: 11319
           Summary: ARM instruction selection failure when
                    -promote-elements=true and -mattr=+neon
           Product: new-bugs
           Version: trunk
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: tzuhsiang.chien at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 7582
  --> http://llvm.org/bugs/attachment.cgi?id=7582
The test cases to reproduce the bug.

When we enable ARM NEON (-mattr=+neon) during the code generation, llc will
return either instruction selection failure or assertion failure on APInt bit
width in some circumstance (see the attached test cases).

After further inspection, we found that only if both of the following flags are
enabled will the bug occur:

(a) -mattr=+neon : This flag enables the code generation for ARM NEON

(b) -promote-elements=true : This flag enables some vector type to vector type
promotion during the legalization process.  This flag has been enabled by
default since revision 142152.


1. Fetch and build the LLVM.

2. Download the attached test case, extract the files, and place them in

3. Run "make check".  The expected behavior is that no additional unexpected
test failure is discovered.  But there will be 6 additional test failures after
adding the attached test cases.

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