[llvm-bugs] [Bug 39160] New: Assertion failure /home/mkazantsev/work/llvm/include/llvm/IR/Instructions.h:3123: llvm::Value* llvm::PHINode::getIncomingValueForBlock(const llvm::BasicBlock*) const: Assertion `Idx >= 0 && "Invalid basic block argument!"' failed. Stack dump:

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39160

            Bug ID: 39160
           Summary: Assertion failure
                    /home/mkazantsev/work/llvm/include/llvm/IR/Instruction
                    s.h:3123: llvm::Value*
                    llvm::PHINode::getIncomingValueForBlock(const
                    llvm::BasicBlock*) const: Assertion `Idx >= 0 &&
                    "Invalid basic block argument!"' failed. Stack dump:
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: max.kazantsev at azul.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 20953
  --> https://bugs.llvm.org/attachment.cgi?id=20953&action=edit
Reproducer IR

Download the IR in attachment and run

opt -loop-vectorizer -S ./ir.ll

It fails an assertion in SCEV like this:

opt: /home/mkazantsev/work/llvm/include/llvm/IR/Instructions.h:3123:
llvm::Value* llvm::PHINode::getIncomingValueForBlock(const llvm::BasicBlock*)
const: Assertion `Idx >= 0 && "Invalid basic block argument!"' failed.
Stack dump:
0.      Program arguments: /home/mkazantsev/work/llvm/build/buildRA/bin/opt
-loop-vectorize -S ./ir.ll
1.      Running pass 'Function Pass Manager' on module './ir.ll'.
2.      Running pass 'Loop Vectorization' on function '@barney'
#0 0x00007f663bb828aa llvm::sys::PrintStackTrace(llvm::raw_ostream&)
/home/mkazantsev/work/llvm/lib/Support/Unix/Signals.inc:494:0
#1 0x00007f663bb80e6a llvm::sys::RunSignalHandlers()
/home/mkazantsev/work/llvm/lib/Support/Signals.cpp:67:0
#2 0x00007f663bb80f9d SignalHandler(int)
/home/mkazantsev/work/llvm/lib/Support/Unix/Signals.inc:353:0
#3 0x00007f663ae9b390 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x11390)
#4 0x00007f663a254428 gsignal
/build/glibc-Cl5G7W/glibc-2.23/signal/../sysdeps/unix/sysv/linux/raise.c:54:0
#5 0x00007f663a25602a abort /build/glibc-Cl5G7W/glibc-2.23/stdlib/abort.c:91:0
#6 0x00007f663a24cbd7 __assert_fail_base
/build/glibc-Cl5G7W/glibc-2.23/assert/assert.c:92:0
#7 0x00007f663a24cc82 (/lib/x86_64-linux-gnu/libc.so.6+0x2dc82)
#8 0x00007f663bd3efd7
(/home/mkazantsev/work/llvm/build/buildRA/bin/../lib/libLLVM-8svn.so+0xc97fd7)
#9 0x00007f663cabf807
llvm::ScalarEvolution::isImpliedViaMerge(llvm::CmpInst::Predicate, llvm::SCEV
const*, llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*, unsigned int)
/home/mkazantsev/work/llvm/lib/Analysis/ScalarEvolution.cpp:10006:0
#10 0x00007f663cabfe42
llvm::ScalarEvolution::isImpliedViaOperations(llvm::CmpInst::Predicate,
llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*,
unsigned int)
/home/mkazantsev/work/llvm/lib/Analysis/ScalarEvolution.cpp:10278:0
#11 0x00007f663cac0241
llvm::ScalarEvolution::isImpliedViaMerge(llvm::CmpInst::Predicate, llvm::SCEV
const*, llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*, unsigned
int)::'lambda0'(llvm::SCEV const*, llvm::SCEV const*)::operator()(llvm::SCEV
const*, llvm::SCEV const*) const
/home/mkazantsev/work/llvm/lib/Analysis/ScalarEvolution.cpp:9965:0
#12 0x00007f663cabf820
llvm::ScalarEvolution::isImpliedViaMerge(llvm::CmpInst::Predicate, llvm::SCEV
const*, llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*, unsigned int)
/home/mkazantsev/work/llvm/lib/Analysis/ScalarEvolution.cpp:10007:0
#13 0x00007f663cabfe42
llvm::ScalarEvolution::isImpliedViaOperations(llvm::CmpInst::Predicate,
llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*,
unsigned int)
/home/mkazantsev/work/llvm/lib/Analysis/ScalarEvolution.cpp:10278:0
#14 0x00007f663cac02cd
llvm::ScalarEvolution::isImpliedCondOperandsHelper(llvm::CmpInst::Predicate,
llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*, llvm::SCEV const*)
/home/mkazantsev/work/llvm/lib/Analysis/ScalarEvolution.cpp:10336:0


The failure is gone is the following patch is reverted:

commit 4090ce2a163b88ef04a8f1a72e421f154c98a1eb
Author: Justin Lebar <jlebar at google.com>
Date:   Thu Jun 14 17:13:35 2018 +0000

    [SCEV] Simplify trunc-of-add/mul to add/mul-of-trunc under more
circumstances.

    Summary:
    Previously we would do this simplification only if it did not introduce
    any new truncs (excepting new truncs which replace other cast ops).

    This change weakens this condition: If the number of truncs stays the
    same, but we're able to transform trunc(X + Y) to X + trunc(Y), that's
    still simpler, and it may open up additional transformations.

    While we're here, also clean up some duplicated code.

    Reviewers: sanjoy

    Subscribers: hiraditya, llvm-commits

    Differential Revision: https://reviews.llvm.org/D48160

    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@334736
91177308-0d34-0410-b5e6-96231b3b80d8



Note that after looking into the patch's code I don't see any obvious problem
there, so it might be not causing the bug but exposing something that's already
there.

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