On 11/17/2015 02:03 PM, Kyrill Tkachov wrote:
+ || !reg_overlap_mentioned_p (tmp_reg, SET_SRC (PATTERN (cand->insn))))
return false;
Well, I think the statement we want to make is
"return false from this function if the two expressions contain the same
register number".
I looked at it again and I think I'll need more time to really figure
out what's going on in this pass.
However, about the above... either I'm very confused, or the actual
statement here is "return false _unless_ the two expressions contain the
same register number". In the testcase, the regs in question are ax and
bx, which is then rejected if the patch has been applied.
(gdb) p tmp_reg
(reg:SI 0 ax)
(gdb) p cand->insn
(insn 59 117 60 7 (set (reg:SI 4 si [orig:107 D.1813 ] [107])
(sign_extend:SI (reg:HI 3 bx [orig:99 D.1813 ] [99])))
And I think it would be better to strengthen that to "return false
unless registers are identical". (From the above it's clear however that
a plain rtx_equal_p wouldn't work since there's an extension in the
operand).
Also, I had another look at the testcase. It uses __builtin_printf and
dg-output, which is at least unusual. Try to use the normal "if (cond)
abort ()".
Bernd
