[llvm-bugs] [Bug 39483] New: Assertion failed: 0 <= InputIdx1 && "Unknown target shuffle input", file E:\work\upstream-llvm\llvm\lib\Target\X86\X86ISelLowering.cpp

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39483

            Bug ID: 39483
           Summary: Assertion failed: 0 <= InputIdx1 && "Unknown target
                    shuffle input", file
                    E:\work\upstream-llvm\llvm\lib\Target\X86\X86ISelLower
                    ing.cpp
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: greg.bedwell at sony.com
                CC: echristo at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk

r345395 ([X86][SSE] Move 2-input limit up from getFauxShuffleMask to
resolveTargetShuffleInputs) introduced a new compiler failure.  This was later
reverted in r345451 due to a report of new failures, but without a testcase
just yet.

I'm not sure if this is the same failure that was observed, but we found this
in our testing so I'm reporting it, as presumably we'll want to re-land r345395
in some form at some point.


$ e:\work\upstream-llvm\build-vs2015-native-ninja\bin\clang.exe --version
clang version 8.0.0 (trunk 345380) (llvm/trunk 345395)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: e:\work\upstream-llvm\build-vs2015-native-ninja\bin

$ cat 1.cpp
struct a {
  float e;
  float f;
  float h;
};
float b(a &c, a &d) { return c.e * d.e + c.f * d.f + c.h * d.h; }
float g[6];
int j;
a *k;
void fn2(a &c) {
  for (int i = 0; i < j; ++i)
    g[i] = b(k[i], c);
}

$ e:\work\upstream-llvm\build-vs2015-native-ninja\bin\clang.exe -c 1.cpp -O2
-march=btver2
Assertion failed: 0 <= InputIdx1 && "Unknown target shuffle input", file
E:\work\upstream-llvm\llvm\lib\Target\X86\X86ISelLowering.cpp, line 30877

I would love to provide a reduced .ll input, but bugpoint has decided so far
not to be cooperative today.  Regardless, the above should be easily usable for
reproducing.

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