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@specialize vs. @inline: @specialize still wins #8247

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scabug opened this issue Feb 6, 2014 · 4 comments
Open

@specialize vs. @inline: @specialize still wins #8247

scabug opened this issue Feb 6, 2014 · 4 comments
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optimizer specialization
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@scabug
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scabug commented Feb 6, 2014 •
edited by eed3si9n

steps

class C[U]() {
  @inline final def apply(x: U): U = x
}

class C2[@specialized(Boolean) U]() {
  @inline final def apply(x: U): U = x
}

class B {
  private val cNormal = new C[Boolean]()
  private val cSpec   = new C2[Boolean]()
  
  final def m1 = cNormal(true)
  final def m2 = cSpec(true)
  // ./a.scala:14: warning: Could not inline required method apply$mcZ$sp because it can be overridden.
  //   final def m2 = cSpec(true)
  //                       ^
  // one warning found

  // however, here it inlines
  cNormal(true)
  cSpec(true)
}

problem

m2 is not inlined.

   0: aload_0
   1: new           #94                 // class C
   4: dup
   5: invokespecial #105                // Method C."<init>":()V
   8: putfield      #69                 // Field cNormal:LC;
  11: aload_0
  12: new           #107                // class C2$mcZ$sp
  15: dup
  16: invokespecial #108                // Method C2$mcZ$sp."<init>":()V
  19: putfield      #73                 // Field cSpec:LC2;
  22: aload_0
  23: invokespecial #77                 // Method cNormal:()LC;
  26: iconst_1
  27: invokestatic  #83                 // Method scala/runtime/BoxesRunTime.boxToBoolean:(Z)Ljava/lang/Boolean;
  30: astore_2
  31: dup
  32: ifnonnull     37
  35: aconst_null
  36: athrow
  37: astore_1
  38: aload_2
  39: astore_3
  40: goto          43
  43: aload_3
  44: pop
  45: aload_0
  46: invokespecial #97                 // Method cSpec:()LC2;
  49: iconst_1
  // **Not inlined**
  50: invokevirtual #103                // Method C2.apply$mcZ$sp:(Z)Z
  53: pop
  54: return

expectation

The bytecode of methods m1 and m2 both are constant true.

original report

I'm not sure I understand what happened in #5005. It's clearly a bug, I opened it with a clear description of the bug, but it ended up being closed because it had become "confused". Okay, I will unconfuse things. Here is the same report again. One should not have to choose between @specialized working and @inline working.
@scabug
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scabug commented Feb 6, 2014

Imported From: https://issues.scala-lang.org/browse/SI-8247?orig=1
Reporter: @paulp
Affected Versions: 2.11.0
See #5005

@scabug scabug added this to the Backlog milestone Apr 7, 2017
@SethTisue
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can someone verify if this is still an issue in Scala 2.12.x?

@neonxray
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neonxray commented Jun 7, 2019 •
edited

@SethTisue In Scala 2.12, it requires option switch -opt:inline or -opt:l:inline and -opt-inline-from:** to enable inlining. But either way it does not seem to work with specialized generic classes.

-opt-inline:

   0: aload_0
   1: new           #94                 // class C
   4: dup
   5: invokespecial #105                // Method C."<init>":()V
   8: putfield      #69                 // Field cNormal:LC;
  11: aload_0
  12: new           #107                // class C2$mcZ$sp
  15: dup
  16: invokespecial #108                // Method C2$mcZ$sp."<init>":()V
  19: putfield      #73                 // Field cSpec:LC2;
  22: aload_0
  23: invokespecial #77                 // Method cNormal:()LC;
  26: iconst_1
  27: invokestatic  #83                 // Method scala/runtime/BoxesRunTime.boxToBoolean:(Z)Ljava/lang/Boolean;
  30: astore_2
  31: dup
  32: ifnonnull     37
  35: aconst_null
  36: athrow
  37: astore_1
  38: aload_2
  39: astore_3
  40: goto          43
  43: aload_3
  44: pop
  45: aload_0
  46: invokespecial #97                 // Method cSpec:()LC2;
  49: iconst_1
  // **Not inlined**
  50: invokevirtual #103                // Method C2.apply$mcZ$sp:(Z)Z
  53: pop
  54: return

-opt:l:inline:

   0: aload_0
   1: new           #89                 // class C
   4: dup
   5: invokespecial #90                 // Method C."<init>":()V
   8: putfield      #69                 // Field cNormal:LC;
  11: aload_0
  12: new           #92                 // class C2$mcZ$sp
  15: dup
  16: invokespecial #93                 // Method C2$mcZ$sp."<init>":()V
  19: putfield      #73                 // Field cSpec:LC2;
  22: aload_0
  23: invokespecial #77                 // Method cNormal:()LC;
  26: ifnonnull     31
  29: aconst_null
  30: athrow
  31: aload_0
  32: invokespecial #80                 // Method cSpec:()LC2;
  35: iconst_1
  // **Not inlined**
  36: invokevirtual #86                 // Method C2.apply$mcZ$sp:(Z)Z
  39: pop
  40: return

@eed3si9n
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eed3si9n commented Jun 9, 2019

@texasbruce Thanks for the verification.

I edited the description of this issue to steps, problem, expectation format.

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