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exp/locale/collate: avoid 16-bit math

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There's no need for the 16-bit arithmetic here,
and it tickles a long-standing compiler bug.
Fix the exp code not to use 16-bit math and
create an explicit test for the compiler bug.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6256048
This commit is contained in:
Russ Cox 2012-05-24 14:50:36 -04:00
parent c44768cb1c
commit ce69666273
2 changed files with 22 additions and 1 deletions
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2
src/pkg/exp/locale/collate/colelem.go
View File

@ -102,7 +102,7 @@ const (
)
func splitContractIndex(ce colElem) (index, n, offset int) {
h := uint16(ce)
h := ce & 0xffff
return int(h >> maxNBits), int(h & (1<<maxNBits - 1)), int(ce>>16) & (1<<maxContractOffsetBits - 1)
}

21
test/bugs/bug440.go Normal file
View File

@ -0,0 +1,21 @@
// $G $D/$F.go && $L $F.$A && ./$A.out
// # switch above to 'run' when bug gets fixed.
// # right now it only breaks on 8g
// Test for 8g register move bug. The optimizer gets confused
// about 16- vs 32-bit moves during splitContractIndex.
package main
func main() {
const c = 0x12345678
index, n, offset := splitContractIndex(c)
if index != int((c&0xffff)>>5) || n != int(c & (1<<5-1)) || offset != (c>>16)&(1<<14-1) {
println("BUG", index, n, offset)
}
}
func splitContractIndex(ce uint32) (index, n, offset int) {
h := uint16(ce)
return int(h >> 5), int(h & (1<<5 - 1)), int(ce>>16) & (1<<14 - 1)
}