[llvm-bugs] [Bug 43723] New: Instruction combining error with llvm.invariant.end intrinsic

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43723

            Bug ID: 43723
           Summary: Instruction combining error with llvm.invariant.end
                    intrinsic
           Product: libraries
           Version: 9.0
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Transformation Utilities
          Assignee: unassignedbugs at nondot.org
          Reporter: kenner at adacore.com
                CC: llvm-bugs at lists.llvm.org

Consider the following small .ll file:

; ModuleID = 'bug17.adb'
source_filename = "bug17.adb"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

define void @_ada_bug17() {
entry:
  %tab = alloca [10 x i8], align 16
  %0 = bitcast [10 x i8]* %tab to i8*
  call void @llvm.memset.p0i8.i64(i8* align 16 %0, i8 9, i64 10, i1 false)
  %1= bitcast [10 x i8]* %tab to i8*
  %2 = call {}* @llvm.invariant.start.p0i8(i64 10, i8* align 16 %1)
  call void @llvm.invariant.end.p0i8({}* %2, i64 10, i8* align 16 %1)
  ret void
}

; Function Attrs: argmemonly nounwind
declare void @llvm.memset.p0i8.i64(i8* nocapture nonnull writeonly, i8, i64, i1 
immarg) #0

; Function Attrs: argmemonly nounwind
declare {}* @llvm.invariant.start.p0i8(i64 immarg, i8* nocapture nonnull
readonl
y) #0

; Function Attrs: argmemonly nounwind
declare void @llvm.invariant.end.p0i8({}*, i64 immarg, i8* nocapture nonnull
rea
donly) #0

This crashes when being optimized with -O1, producing:

IC: ERASE   %0 = call {}* @llvm.invariant.start.p0i8(i64 10, i8* align 16
undef)
opt:
/llvm.a/gnat-llvm/llvm/llvm-9.0.0.src/lib/Transforms/InstCombine/InstCombineInternal.h:646:
llvm::Instruction*
llvm::InstCombiner::eraseInstFromFunction(llvm::Instruction&): Assertion
`I.use_empty() && "Cannot erase instruction that is used!"' failed.

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