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Combine on IA-64
- From: Jakub Jelinek <jakub at redhat dot com>
- To: gcc at gcc dot gnu dot org
- Date: Tue, 26 Feb 2002 14:50:31 +0100
- Subject: Combine on IA-64
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
With the visibility patch I've noticed IA-64 generates
pretty inefficient code like:
addl r15 = @gprel(l#), gp
addl r16 = @gprel(m#), gp
;;
.mii
// cycle 1
adds r15 = 10, r15
adds r16 = 10, r16
instead of:
addl r15 = @gprel(l#+10), gp
addl r16 = @gprel(m#+10), gp
I've tried to fix this using peephole2, but that doesn't work too well,
since the two instructions aren't usually adjacent.
Now, as I understand, symbolic_operand accepts
(const (plus:DI (symbol_ref:DI ("@foo")) (const_int )))
just fine, so this looks like combiner inefficiency.
try_combine for:
i2:
(insn 9 18 12 (parallel[
(set (reg/f:DI 340)
(symbol_ref:DI ("@l")))
(clobber (reg:DI 341))
(use (reg:DI 1 r1))
] ) 5 {movdi_symbolic} (nil)
(expr_list:REG_UNUSED (reg:DI 341)
(expr_list:REG_EQUAL (symbol_ref:DI ("@l"))
(nil))))
i3:
(insn 12 9 14 (set (reg/f:DI 343)
(plus:DI (reg/f:DI 340)
(const_int 10 [0xa]))) 90 {adddi3} (insn_list 9 (nil))
(expr_list:REG_DEAD (reg/f:DI 340)
(expr_list:REG_EQUAL (const:DI (plus:DI (symbol_ref:DI ("@l"))
(const_int 10 [0xa])))
(nil))))
only attempts to recognize:
(set (reg/f:DI 343)
(const (plus:DI (symbol_ref:DI ("@l"))
(const_int 10 [0xa]))))
and not
(parallel[
(set (reg/f:DI 343)
(const (plus:DI (symbol_ref:DI ("@l"))
(const_int 10 [0xa]))))
(clobber (reg:DI 341))
(use (reg:DI 1 r1))
] )
Cannot this be special cased in try_combine (there is already some other
similar special case which fails because i3's SET_SRC is not
register but PLUS) provided the clobbers aren't mentioned between i2 and i3
and uses are not modified in between?
Jakub