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[SR-7763] Optimization forms illegal shift node #50302

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stephentyrone opened this issue May 24, 2018 · 8 comments
Closed

[SR-7763] Optimization forms illegal shift node #50302

stephentyrone opened this issue May 24, 2018 · 8 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software optimized only Flag: An issue whose reproduction requires optimized compilation

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@stephentyrone
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Previous ID SR-7763
Radar rdar://problem/40555524
Original Reporter @stephentyrone
Type Bug
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, CompilerCrash, OptimizedOnly
Assignee None
Priority Medium

md5: 05528d753c6ad92bed689b3bfc2003e9

Issue Description:

https://godbolt.org/g/94XBpN

import Swift

public struct Float16 {
  public var _value: Builtin.FPIEEE16
  
  public var bitPattern: UInt16 {
    return UInt16(Builtin.bitcast_FPIEEE16_Int16(_value))
  }
  
  public var sign: FloatingPointSign {
    return FloatingPointSign(rawValue: Int(bitPattern >> 15))!
  }
}

Compiling with -parse-stdlib -O fails in LLVM:

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp:4168: llvm::SDValue llvm::SelectionDAG::getNode(unsigned int, const llvm::SDLoc &, llvm::EVT, llvm::SDValue, llvm::SDValue, const llvm::SDNodeFlags): Assertion `VT == N1.getValueType() && "Shift operators return type must be the same as their first arg"' failed.

I haven't had time to investigate this much, so I'm not sure where in the process the bad node is getting formed.
@stephentyrone
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Does not occur with optimization turned off. Present in both shipping 4.x and ToT.

@belkadan
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cc aschwaighofer@apple.com (JIRA User)

@belkadan
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@swift-ci create

@aschwaighofer
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LLVM bug

$ cat c.ll
define i8 @crash(half)  {
entry:
  %1 = bitcast half %0 to i16
  %.lobit = lshr i16 %1, 15
  %2 = trunc i16 %.lobit to i8
  ret i8 %2
}

$ build01/llvm-macosx-x86_64/bin/llc c.ll
Assertion failed: (VT == N1.getValueType() && "Shift operators return type must be the same as their first arg"), function getNode, file /Users/arnold/Github/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp, line 4351.

@stephentyrone
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https://bugs.llvm.org/show_bug.cgi?id=38038

@belkadan
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belkadan commented Apr 4, 2019

The Apple LLVM folks fixed this for Swift 5.

@stephentyrone
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@belkadan I wasn't aware I was one of the "LLVM folks" now =)

@belkadan
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belkadan commented Apr 4, 2019

Oops, I didn't see that it was your fix rather than Ahmed's. But I suppose that makes you an LLVM folks anyway!

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@AnthonyLatsis AnthonyLatsis added the crash Bug: A crash, i.e., an abnormal termination of software label Dec 12, 2022
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself crash Bug: A crash, i.e., an abnormal termination of software optimized only Flag: An issue whose reproduction requires optimized compilation
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@stephentyrone @belkadan @aschwaighofer @AnthonyLatsis