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[dev.ssa] cmd/compile: fix stackalloc handling of zero-aligned variables
Prior to this fix, a zero-aligned variable such as a flags variable would reset n to 0. While we're here, log the stack layout so that debugging and reading the generated assembly is easier. Change-Id: I18ef83ea95b6ea877c83f2e595e14c48c9ad7d84 Reviewed-on: https://go-review.googlesource.com/12439 Reviewed-by: Keith Randall <khr@golang.org>
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@ -20,6 +20,7 @@ func stackalloc(f *Func) {
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n = v.AuxInt
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}
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}
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f.Logf("stackalloc: 0-%d for callee arguments/returns\n", n)
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// TODO: group variables by ptr/nonptr, size, etc. Emit ptr vars last
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// so stackmap is smaller.
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@ -36,6 +37,7 @@ func stackalloc(f *Func) {
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continue
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}
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n = align(n, v.Type.Alignment())
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f.Logf("stackalloc: %d-%d for %v\n", n, n+v.Type.Size(), v)
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loc := &LocalSlot{n}
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n += v.Type.Size()
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home = setloc(home, v, loc)
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@ -62,6 +64,7 @@ func stackalloc(f *Func) {
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continue
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}
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n = align(n, v.Type.Alignment())
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f.Logf("stackalloc: %d-%d for %v\n", n, n+v.Type.Size(), v)
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loc := &LocalSlot{n}
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n += v.Type.Size()
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home = setloc(home, v, loc)
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@ -77,12 +80,14 @@ func stackalloc(f *Func) {
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}
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t := s.Typ
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n = align(n, t.Alignment())
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f.Logf("stackalloc: %d-%d for auto %v\n", n, n+t.Size(), v)
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s.Offset = n
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n += t.Size()
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}
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}
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n = align(n, f.Config.PtrSize)
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f.Logf("stackalloc: %d-%d for return address\n", n, n+f.Config.ptrSize)
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n += f.Config.PtrSize // space for return address. TODO: arch-dependent
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f.RegAlloc = home
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f.FrameSize = n
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@ -92,5 +97,8 @@ func stackalloc(f *Func) {
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// align increases n to the next multiple of a. a must be a power of 2.
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func align(n int64, a int64) int64 {
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if a == 0 {
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return n
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}
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return (n + a - 1) &^ (a - 1)
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}
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