issue24799.go

     1  // run
     2  
     3  // Copyright 2018 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Loads of 8 byte go.strings cannot use DS relocation
     8  // in case the alignment is not a multiple of 4.
     9  
    10  package main
    11  
    12  import (
    13          "fmt"
    14  )
    15  
    16  type Level string
    17  
    18  // The following are all go.strings. A link time error can
    19  // occur if an 8 byte load is used to load a go.string that is
    20  // not aligned to 4 bytes due to the type of relocation that
    21  // is generated for the instruction. A fix was made to avoid
    22  // generating an instruction with DS relocation for go.strings
    23  // since their alignment is not known until link time. 
    24  
    25  // This problem only affects go.string since other types have
    26  // correct alignment.
    27  
    28  const (
    29          LevelBad Level = "badvals"
    30          LevelNone Level = "No"
    31          LevelMetadata Level = "Metadata"
    32          LevelRequest Level = "Request"
    33          LevelRequestResponse Level = "RequestResponse"
    34  )
    35  
    36  func ordLevel(l Level) int {
    37          switch l {
    38          case LevelMetadata:
    39                  return 1
    40          case LevelRequest:
    41                  return 2
    42          case LevelRequestResponse:
    43                  return 3
    44          default:
    45                  return 0
    46          }
    47  }
    48  
    49  //go:noinline
    50  func test(l Level) {
    51          if ordLevel(l) < ordLevel(LevelMetadata) {
    52                  fmt.Printf("OK\n")
    53          }
    54  }
    55  
    56  func main() {
    57          test(LevelMetadata)
    58  }
    59
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