reuse previous address constants in fold()
parseref() has code to reuse address constants, but this is not done in other passes such as fold or isel. Introduce a new function newcon() which takes a Con and returns a Ref for that constant, and use this whenever creating address constants. This is necessary to fix folding of address constants when one operand is already folded. For example, in %a =l add $x, 1 %b =l add %a, 2 %c =w loadw %b %a and %b were folded to $x+1 and $x+3 respectively, but then the second add is visited again since it uses %a. This gets folded to $x+3 as well, but as a new distinct constant. This results in %b getting labeled as bottom instead of either constant, disabling the replacement of %b by a constant in subsequent instructions (such as the loadw).
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6 changed files with 33 additions and 31 deletions
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@ -117,12 +117,9 @@ fixarg(Ref *r, int k, Ins *i, Fn *fn)
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m = &fn->mem[r0.val];
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if (req(m->base, R))
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if (m->offset.type == CAddr) {
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n = fn->ncon;
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vgrow(&fn->con, ++fn->ncon);
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fn->con[n] = m->offset;
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m->offset.type = CUndef;
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r0 = newtmp("isel", Kl, fn);
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emit(Oaddr, Kl, r0, CON(n), R);
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emit(Oaddr, Kl, r0, newcon(&m->offset, fn), R);
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m->offset.type = CUndef;
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m->base = r0;
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}
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}
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