issue68227.go

     1  // run
     2  
     3  // Copyright 2024 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  package main
     8  
     9  import (
    10  	"fmt"
    11  )
    12  
    13  type someType []uint64
    14  
    15  func (s *someType) push(v uint64) {
    16  	*s = append(*s, v)
    17  }
    18  
    19  func (s *someType) problematicFn(x1Lo, x1Hi, x2Lo, x2Hi uint64) {
    20  	r1 := int32(int16(x1Lo>>0)) * int32(int16(x2Lo>>0))
    21  	g()
    22  	r3 := int32(int16(x1Lo>>32)) * int32(int16(x2Lo>>32))
    23  	r4 := int32(int16(x1Lo>>48)) * int32(int16(x2Lo>>48))
    24  	r5 := int32(int16(x1Hi>>0)) * int32(int16(x2Hi>>0))
    25  	r7 := int32(int16(x1Hi>>32)) * int32(int16(x2Hi>>32))
    26  	r8 := int32(int16(x1Hi>>48)) * int32(int16(x2Hi>>48))
    27  	s.push(uint64(uint32(r1)) | (uint64(uint32(r3+r4)) << 32))
    28  	s.push(uint64(uint32(r5)) | (uint64(uint32(r7+r8)) << 32))
    29  }
    30  
    31  //go:noinline
    32  func g() {
    33  }
    34  
    35  func main() {
    36  	s := &someType{}
    37  	s.problematicFn(0x1000100010001, 0x1000100010001, 0xffffffffffffffff, 0xffffffffffffffff)
    38  	for i := 0; i < 2; i++ {
    39  		if got, want := (*s)[i], uint64(0xfffffffeffffffff); got != want {
    40  			fmt.Printf("s[%d]=%x, want %x\n", i, got, want)
    41  		}
    42  	}
    43  }
    44
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