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cmd/compile: remove 68857 min & max flowLimit workaround in prove

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We can know this is correct because all the testcases added by CL 656157 are still passing.
Partial revert of CL 656157 (everything but the testcases).

Change-Id: I24931fa1affba7e9e92233b3de74ebade3d48a09
Reviewed-on: https://go-review.googlesource.com/c/go/+/714921
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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Jorropo 2025-10-25 15:34:02 +02:00 • committed by Gopher Robot
parent 53be78630a
commit a50de4bda7
1 changed files with 0 additions and 83 deletions
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83
src/cmd/compile/internal/ssa/prove.go
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@ -1996,89 +1996,6 @@ func (ft *factsTable) flowLimit(v *Value) bool {
return ft.newLimit(v, lim)
case OpPhi:
{
// Work around for go.dev/issue/68857, look for min(x, y) and max(x, y).
b := v.Block
if len(b.Preds) != 2 {
goto notMinNorMax
}
// FIXME: this code searches for the following losange pattern
// because that what ssagen produce for min and max builtins:
// conditionBlock → (firstBlock, secondBlock) → v.Block
// there are three non losange equivalent constructions
// we could match for, but I didn't bother:
// conditionBlock → (v.Block, secondBlock → v.Block)
// conditionBlock → (firstBlock → v.Block, v.Block)
// conditionBlock → (v.Block, v.Block)
firstBlock, secondBlock := b.Preds[0].b, b.Preds[1].b
if firstBlock.Kind != BlockPlain || secondBlock.Kind != BlockPlain {
goto notMinNorMax
}
if len(firstBlock.Preds) != 1 || len(secondBlock.Preds) != 1 {
goto notMinNorMax
}
conditionBlock := firstBlock.Preds[0].b
if conditionBlock != secondBlock.Preds[0].b {
goto notMinNorMax
}
if conditionBlock.Kind != BlockIf {
goto notMinNorMax
}
less := conditionBlock.Controls[0]
var unsigned bool
switch less.Op {
case OpLess64U, OpLess32U, OpLess16U, OpLess8U,
OpLeq64U, OpLeq32U, OpLeq16U, OpLeq8U:
unsigned = true
case OpLess64, OpLess32, OpLess16, OpLess8,
OpLeq64, OpLeq32, OpLeq16, OpLeq8:
default:
goto notMinNorMax
}
small, big := less.Args[0], less.Args[1]
truev, falsev := v.Args[0], v.Args[1]
if conditionBlock.Succs[0].b == secondBlock {
truev, falsev = falsev, truev
}
bigl, smalll := ft.limits[big.ID], ft.limits[small.ID]
if truev == big {
if falsev == small {
// v := big if small <¿=? big else small
if unsigned {
maximum := max(bigl.umax, smalll.umax)
minimum := max(bigl.umin, smalll.umin)
return ft.unsignedMinMax(v, minimum, maximum)
} else {
maximum := max(bigl.max, smalll.max)
minimum := max(bigl.min, smalll.min)
return ft.signedMinMax(v, minimum, maximum)
}
} else {
goto notMinNorMax
}
} else if truev == small {
if falsev == big {
// v := small if small <¿=? big else big
if unsigned {
maximum := min(bigl.umax, smalll.umax)
minimum := min(bigl.umin, smalll.umin)
return ft.unsignedMinMax(v, minimum, maximum)
} else {
maximum := min(bigl.max, smalll.max)
minimum := min(bigl.min, smalll.min)
return ft.signedMinMax(v, minimum, maximum)
}
} else {
goto notMinNorMax
}
} else {
goto notMinNorMax
}
}
notMinNorMax:
// Compute the union of all the input phis.
// Often this will convey no information, because the block
// is not dominated by its predecessors and hence the