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[dev.ssa] cmd/compile: cse should treat -0.0 and 0.0 as different
cse was incorrectly classifying -0.0 and 0.0 as equivalent. This lead to invalid code as ssa uses PXOR -0.0, reg to negate a floating point. Fixes math. Change-Id: Id7eb10c71749eaed897f29b02c33891cf5820acf Reviewed-on: https://go-review.googlesource.com/14205 Reviewed-by: Keith Randall <khr@golang.org>
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@ -44,6 +44,7 @@ Optimizations (better compiler)
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- Reuseable slices (e.g. []int of size NumValues()) cached in Func
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- Handle signed division overflow and sign extension earlier
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- Implement 64 bit const division with high multiply, maybe in the frontend?
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- Store bool and float32/float64 in auxInt
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Regalloc
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--------
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@ -4,7 +4,10 @@
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package ssa
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import "sort"
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import (
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"math"
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"sort"
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)
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// cse does common-subexpression elimination on the Function.
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// Values are just relinked, nothing is deleted. A subsequent deadcode
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@ -51,7 +54,19 @@ func cse(f *Func) {
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if len(v.Args) > 1 {
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arg1op = v.Args[1].Op
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}
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k := key{v.Op, v.Type.String(), v.Aux, v.AuxInt, len(v.Args), bid, arg0op, arg1op}
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aux := v.Aux
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auxInt := v.AuxInt
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// -0 == 0, but aren't equivalent values so we use
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// Float64bits to distinguish
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if f, ok := aux.(float64); ok {
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aux = nil
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if auxInt != 0 {
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v.Fatalf("float would clobber v.auxInt")
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}
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auxInt = int64(math.Float64bits(f))
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}
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k := key{v.Op, v.Type.String(), aux, auxInt, len(v.Args), bid, arg0op, arg1op}
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m[k] = append(m[k], v)
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}
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}
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