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cmd/compile: add Sext support to known bits

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This doesn't have any hits in the std.

Updates #78633

Change-Id: I965838f876e90189f546355093997d64ec13cb35
Reviewed-on: https://go-review.googlesource.com/c/go/+/765802
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Jorropo 2026-04-12 09:59:20 +02:00 • committed by Gopher Robot
parent d75902b195
commit 8963c303b4
2 changed files with 18 additions and 2 deletions
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5
src/cmd/compile/internal/ssa/known_bits.go
View file

@ -44,7 +44,7 @@ func (kb *knownBitsState) fold(v *Value) (value, known int64) {
kb.seenValues.Set(uint32(v.ID)) // set seen early to give up on loops
switch v.Op {
// TODO: Shifts, rotates, extensions, ...
// TODO: Shifts, rotates, ...
case OpConst64, OpConst32, OpConst16, OpConst8, OpConstBool:
return v.AuxInt, -1
case OpAnd64, OpAnd32, OpAnd16, OpAnd8, OpAndB:
@ -87,7 +87,8 @@ func (kb *knownBitsState) fold(v *Value) (value, known int64) {
}
}
return value, known
case OpCopy, OpCvtBoolToUint8:
case OpCopy, OpCvtBoolToUint8,
OpSignExt8to16, OpSignExt8to32, OpSignExt8to64, OpSignExt16to32, OpSignExt16to64, OpSignExt32to64:
return kb.fold(v.Args[0])
case OpEq64, OpEq32, OpEq16, OpEq8, OpEqB:
x, xk := kb.fold(v.Args[0])

15
test/known_bits.go
View file

@ -214,3 +214,18 @@ func knownBitsCvtBoolToUint8True(x int64, cond bool) uint8 {
func unknownBitsCvtBoolToUint8(cond bool) uint8 {
return cvtBoolToUint8(cond) & 1
}
func knownBitsSignExtPassThrough(x int8) int64 {
x |= 6
return int64(x) & 6 // ERROR "known value of v[0-9]+ \(And64\): 6$"
}
func knownBitsSignExtUpperHalf(x int16) int32 {
x |= -1 << 15
return int32(x) & (-1 << 16) // ERROR "known value of v[0-9]+ \(And32\): -65536$"
}
func unknownBitsSignExt(x int16) int32 {
x |= -0b010101010101010
return int32(x) & -1 << 12
}