[LLVMbugs] [Bug 14519] New: Tablegen-generated Intrinsic string compares mis-sorted

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=14519

             Bug #: 14519
           Summary: Tablegen-generated Intrinsic string compares
                    mis-sorted
           Product: new-bugs
           Version: 3.1
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: richard.relph at amd.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


In the tablegen-generated file AMDILGenIntrinsics.inc, we have a bunch of if
statements comparing strings, many of which are dead, preventing correct
recognition of some intrinsics in the their text form. I'm not quite sure what
GET_FUNCTION_RECOGNIZER is used for, but if it's used, it's broken… ;-)

Here's a small segment:

// Function name -> enum value recognizer code.
#ifdef GET_FUNCTION_RECOGNIZER
StringRef NameR(Name+6, Len-6);   // Skip over 'llvm.'
switch (Name[5]) {                  // Dispatch on first letter.
default: break;
case 'A':
…
if (NameR.startswith("MDIL.barrier.")) return AMDILIntrinsic::AMDIL_barrier;
if (NameR.startswith("MDIL.barrier.global.")) return
AMDILIntrinsic::AMDIL_barrier_global;
if (NameR.startswith("MDIL.barrier.local.")) return
AMDILIntrinsic::AMDIL_barrier_local;
if (NameR.startswith("MDIL.barrier.region.")) return
AMDILIntrinsic::AMDIL_barrier_region;
…
if (NameR.startswith("MDIL.fma.")) return AMDILIntrinsic::AMDIL_fma;
if (NameR.startswith("MDIL.fma.rte.")) return AMDILIntrinsic::AMDIL_fma_rte;
if (NameR.startswith("MDIL.fma.rtn.")) return AMDILIntrinsic::AMDIL_fma_rtn;
if (NameR.startswith("MDIL.fma.rtp.")) return AMDILIntrinsic::AMDIL_fma_rtp;
if (NameR.startswith("MDIL.fma.rtz.")) return AMDILIntrinsic::AMDIL_fma_rtz;
…
and several other similar instances.

The problem is that AMDIL.barrier.global will match the earlier startswith()
AMDIL.barrier test and return the wrong intrinsic enum. Similarly
AMDIL.fma.rte/n/p/z.

The string compares are obviously sorted by tablegen, but should be emitted in
reverse sort order.

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