diff options
Diffstat (limited to 'src/cmd/compile/internal/ssa/prove.go')
| -rw-r--r-- | src/cmd/compile/internal/ssa/prove.go | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go index c9f75daa67..1083874100 100644 --- a/src/cmd/compile/internal/ssa/prove.go +++ b/src/cmd/compile/internal/ssa/prove.go @@ -2187,24 +2187,22 @@ func (ft *factsTable) detectSubRelations(v *Value) { return // x-y might overflow } - // Subtracting a positive number only makes - // things smaller. - if yLim.min >= 0 { + // Subtracting a positive non-zero number only makes + // things smaller. If it's positive or zero, it might + // also do nothing (x-0 == v). + if yLim.min > 0 { + ft.update(v.Block, v, x, signed, lt) + } else if yLim.min == 0 { ft.update(v.Block, v, x, signed, lt|eq) - // TODO: is this worth it? - //if yLim.min > 0 { - // ft.update(v.Block, v, x, signed, lt) - //} } // Subtracting a number from a bigger one - // can't go below 0. - if ft.orderS.OrderedOrEqual(y, x) { + // can't go below 1. If the numbers might be + // equal, then it can't go below 0. + if ft.orderS.Ordered(y, x) { + ft.signedMin(v, 1) + } else if ft.orderS.OrderedOrEqual(y, x) { ft.setNonNegative(v) - // TODO: is this worth it? - //if ft.orderS.Ordered(y, x) { - // ft.signedMin(v, 1) - //} } } |