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| author | Jorropo <jorropo.pgm@gmail.com> | 2025-12-07 03:07:46 +0100 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2026-01-23 12:08:57 -0800 |
| commit | 417d5e6627dbef2e6a309957b4f932eb91ce1e4d (patch) | |
| tree | d442a69a64a620caed38d5a05fded593e7ada398 /src | |
| parent | a4fda8d32ac30b787cf2c648daed7f8fe5ef859d (diff) | |
| download | go-417d5e6627dbef2e6a309957b4f932eb91ce1e4d.tar.xz | |
cmd/compile: add limits bruteforce tests for bitlen
This ensure BitLen is perfect within the limitations limits can represent.
Change-Id: I5c1770b4a9f6408fd68fe77b4ef2b2cdd52e26cb
Reviewed-on: https://go-review.googlesource.com/c/go/+/727781
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Diffstat (limited to 'src')
| -rw-r--r-- | src/cmd/compile/internal/ssa/prove.go | 32 | ||||
| -rw-r--r-- | src/cmd/compile/internal/ssa/prove_test.go | 4 |
2 files changed, 16 insertions, 20 deletions
diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go index 22de2dc7a5..233d0b30d1 100644 --- a/src/cmd/compile/internal/ssa/prove.go +++ b/src/cmd/compile/internal/ssa/prove.go @@ -428,6 +428,14 @@ func (l limit) ctz(b uint) limit { return noLimit.unsignedMax(uint64(min(uint(bits.TrailingZeros64(fixed)), b))) } +// Similar to add, but computes the Len of the limit for bitsize b. +func (l limit) bitlen(b uint) limit { + return noLimit.unsignedMinMax( + uint64(bits.Len64(l.umin)), + uint64(bits.Len64(l.umax)), + ) +} + var noLimit = limit{math.MinInt64, math.MaxInt64, 0, math.MaxUint64} // a limitFact is a limit known for a particular value. @@ -1941,26 +1949,10 @@ func (ft *factsTable) flowLimit(v *Value) { min := uint64(bits.OnesCount64(fixedBits)) ft.unsignedMinMax(v, min, min+changingBitsCount) - case OpBitLen64: - a := ft.limits[v.Args[0].ID] - ft.unsignedMinMax(v, - uint64(bits.Len64(a.umin)), - uint64(bits.Len64(a.umax))) - case OpBitLen32: - a := ft.limits[v.Args[0].ID] - ft.unsignedMinMax(v, - uint64(bits.Len32(uint32(a.umin))), - uint64(bits.Len32(uint32(a.umax)))) - case OpBitLen16: - a := ft.limits[v.Args[0].ID] - ft.unsignedMinMax(v, - uint64(bits.Len16(uint16(a.umin))), - uint64(bits.Len16(uint16(a.umax)))) - case OpBitLen8: - a := ft.limits[v.Args[0].ID] - ft.unsignedMinMax(v, - uint64(bits.Len8(uint8(a.umin))), - uint64(bits.Len8(uint8(a.umax)))) + case OpBitLen64, OpBitLen32, OpBitLen16, OpBitLen8: + a := v.Args[0] + al := ft.limits[a.ID] + ft.newLimit(v, al.bitlen(uint(a.Type.Size())*8)) // Masks. diff --git a/src/cmd/compile/internal/ssa/prove_test.go b/src/cmd/compile/internal/ssa/prove_test.go index 1d91736ff0..969e68fee4 100644 --- a/src/cmd/compile/internal/ssa/prove_test.go +++ b/src/cmd/compile/internal/ssa/prove_test.go @@ -77,3 +77,7 @@ func TestLimitComUnsigned(t *testing.T) { func TestLimitCtzUnsigned(t *testing.T) { testLimitUnaryOpUnsigned8(t, "ctz", limit{-128, 127, 0, 8}, limit.ctz, func(x uint8) uint8 { return uint8(bits.TrailingZeros8(x)) }) } + +func TestLimitBitlenUnsigned(t *testing.T) { + testLimitUnaryOpUnsigned8(t, "bitlen", limit{-128, 127, 0, 8}, limit.bitlen, func(x uint8) uint8 { return uint8(bits.Len8(x)) }) +} |