Fix 63615 - FAIL: gcc.target/i386/addr-sel-1.c

[Jeff Law]

On 10/23/14 00:56, Alan Modra wrote:
> PR 63615 was caused by r21642 fixing the accounting of "n_constants"
> in simplify_plus_minus.  Previously, any expression handled by
> simplify_plus_minus that expanded to more than two elements and
> contained at least one constant would have resulted in "n_constants"
> being larger than one, even if it had only one constant.  This had the
> effect of setting "canonicalized" for such expressions.
>
> The missed optimisation had these operands to simplify_plus_minus:
> (gdb) p debug_rtx(op0)
> (plus:SI (reg:SI 0 ax [96])
>      (const_int 1 [0x1]))
> $1 = void
> (gdb) p debug_rtx(op1)
> (symbol_ref:SI ("a") <var_decl 0x7ffff6c2f900 a>)
> $2 = void
>
> resulting in the ops array being populated as
> (gdb) p n_ops
> $3 = 3
> (gdb) p ops[0]@3
> $4 = {{op = 0x7ffff6d4b360, neg = 0}, {op = 0x7ffff6d483a8, neg = 0}, {op = 0x7ffff6c29490, neg = 0}}
> (gdb) p debug_rtx(ops[0].op)
> (reg:SI 0 ax [96])
> $5 = void
> (gdb) p debug_rtx(ops[1].op)
> (symbol_ref:SI ("a") <var_decl 0x7ffff6c2f900 a>)
> $6 = void
> (gdb) p debug_rtx(ops[2].op)
> (const_int 1 [0x1])
> $7 = void
>
> Of note here is that the operands have been reordered from their
> original positions.  What was ax + 1 + sym is now ax + sym + 1, and it
> happens that this ordering is correct in the sense that
> simplify_plus_minus_op_data_cmp sorting of the ops array produces no
> changes.  Now any change made during sorting sets "canonicalized", so
> I figure reordering while decomposing operands ought to set
> "canonicalized" too.  Indeed, the reordering seen above has
> canonicalized the expression.  (Of course the reordering during
> decomposition might be exactly cancelled by later sorting, but it
> hardly seems worth fixing that, and other cases where we might return
> the input expression unchanged..)
>
> I'm still running bootstrap and regression tests on x86_64-linux,
> this time with both -m64 and -m32 regression tests.
> OK to apply assuming no regressions?
>
> 	PR rtl-optimization/63615
> 	* simplify-rtx.c (simplify_plus_minus): Set "canonicalized" on
> 	decomposing PLUS or MINUS if operands are not placed adjacent
> 	in the "ops" array.
OK assuming no regressions.

jeff