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cmd/compile: clarify unsigned interpretation of AuxInt

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The way Value.AuxInt represents unsigned numbers is currently
documented in genericOps.go, which is not the most obvious place for
it. Move that documentation to Value.AuxInt. Furthermore, to make it
harder to use incorrectly, introduce a Value.AuxUnsigned accessor that
returns the zero-extended value of Value.AuxInt.

Change-Id: I85030c3c68761404058a430e0b1c7464591b2f42
Reviewed-on: https://go-review.googlesource.com/102597
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Austin Clements 2018-03-25 12:20:57 -04:00
parent a29e25b82c
commit 2d8181e7b5
3 changed files with 25 additions and 14 deletions
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14
src/cmd/compile/internal/ssa/prove.go
View file

@ -234,7 +234,6 @@ func (ft *factsTable) update(parent *Block, v, w *Value, d domain, r relation) {
r = reverseBits[r]
}
if v != nil && w.isGenericIntConst() {
c := w.AuxInt
// Note: all the +1/-1 below could overflow/underflow. Either will
// still generate correct results, it will just lead to imprecision.
// In fact if there is overflow/underflow, the corresponding
@ -247,6 +246,7 @@ func (ft *factsTable) update(parent *Block, v, w *Value, d domain, r relation) {
lim := noLimit
switch d {
case signed:
c := w.AuxInt
switch r {
case lt:
lim.max = c - 1
@ -279,17 +279,7 @@ func (ft *factsTable) update(parent *Block, v, w *Value, d domain, r relation) {
lim.umax = uint64(lim.max)
}
case unsigned:
var uc uint64
switch w.Op {
case OpConst64:
uc = uint64(c)
case OpConst32:
uc = uint64(uint32(c))
case OpConst16:
uc = uint64(uint16(c))
case OpConst8:
uc = uint64(uint8(c))
}
uc := w.AuxUnsigned()
switch r {
case lt:
lim.umax = uc - 1