ping
чт, 20 июн. 2024 г. в 12:09, Siarhei Volkau <lis8...@gmail.com>: > > This patch deals with consequences but not the root cause though. > > There are 5 cases which are subjects to rewrite: > case #1: > mov ip, r1 > add r2, ip > # ip is dead here > can be rewritten as: > adds r2, r1 > > case #2: > add ip, r1 > mov r1, ip > # ip is dead here > can be rewritten as: > add r1, ip > > case #3: > mov ip, r1 > add r2, ip > add r3, ip > # ip is dead here > can be rewritten as: > adds r2, r1 > adds r3, r1 > > case #4: > mov ip, r1 > add ip, r2 > mov r1, ip > can be rewritten as: > adds r1, r2 > mov ip, r1 <- might be eliminated too, if ip is dead > > case #5 (arbitrary): > mov r1, ip > subs r2, r1, r2 > mov ip, r2 > # r1 is dead here > can be rewritten as: > rsbs r1, r2, #0 > add ip, r1 > movs r2, ip <- might be eliminated, if r2 is dead > > Speed profit wasn't checked but size changes are the following: > libgcc: -132 bytes / -0.25% > libc: -1262 bytes / -0.55% > libm: -384 bytes / -0.42% > libstdc++: -2258 bytes / -0.30% > > No tests provided because its hard to force GCC to emit HI_REGS > in a small and straightforward function. > > Signed-off-by: Siarhei Volkau <lis8...@gmail.com> > --- > gcc/config/arm/thumb1.md | 93 +++++++++++++++++++++++++++++++++++++++- > 1 file changed, 92 insertions(+), 1 deletion(-) > > diff --git a/gcc/config/arm/thumb1.md b/gcc/config/arm/thumb1.md > index d7074b43f60..9da4af9eccd 100644 > --- a/gcc/config/arm/thumb1.md > +++ b/gcc/config/arm/thumb1.md > @@ -2055,4 +2055,95 @@ (define_insn "thumb1_stack_protect_test_insn" > (set_attr "conds" "clob") > (set_attr "type" "multiple")] > ) > - > + > +;; bad code emitted when HI_REGS involved in addition > +;; subtract also might happen rarely > + > +;; case #1: > +;; mov ip, r1 > +;; add r2, ip # ip is dead after that > +(define_peephole2 > + [(set (match_operand:SI 0 "register_operand" "") > + (match_operand:SI 1 "register_operand" "")) > + (set (match_operand:SI 2 "register_operand" "") > + (plus:SI (match_dup 2) (match_dup 0)))] > + "TARGET_THUMB1 > + && peep2_reg_dead_p (2, operands[0]) > + && REGNO_REG_CLASS (REGNO (operands[0])) == HI_REGS" > + [(set (match_dup 2) > + (plus:SI (match_dup 2) (match_dup 1)))] > + "") > + > +;; case #2: > +;; add ip, r1 > +;; mov r1, ip # ip is dead after that > +(define_peephole2 > + [(set (match_operand:SI 0 "register_operand" "") > + (plus:SI (match_dup 0) (match_operand:SI 1 "register_operand" ""))) > + (set (match_dup 1) (match_dup 0))] > + "TARGET_THUMB1 > + && peep2_reg_dead_p (2, operands[0]) > + && REGNO_REG_CLASS (REGNO (operands[0])) == HI_REGS" > + [(set (match_dup 1) > + (plus:SI (match_dup 1) (match_dup 0)))] > + "") > + > +;; case #3: > +;; mov ip, r1 > +;; add r2, ip > +;; add r3, ip # ip is dead after that > +(define_peephole2 > + [(set (match_operand:SI 0 "register_operand" "") > + (match_operand:SI 1 "register_operand" "")) > + (set (match_operand:SI 2 "register_operand" "") > + (plus:SI (match_dup 2) (match_dup 0))) > + (set (match_operand:SI 3 "register_operand" "") > + (plus:SI (match_dup 3) (match_dup 0)))] > + "TARGET_THUMB1 > + && peep2_reg_dead_p (3, operands[0]) > + && REGNO_REG_CLASS (REGNO (operands[0])) == HI_REGS" > + [(set (match_dup 2) > + (plus:SI (match_dup 2) (match_dup 1))) > + (set (match_dup 3) > + (plus:SI (match_dup 3) (match_dup 1)))] > + "") > + > +;; case #4: > +;; mov ip, r1 > +;; add ip, r2 > +;; mov r1, ip > +(define_peephole2 > + [(set (match_operand:SI 0 "register_operand" "") > + (match_operand:SI 1 "register_operand" "")) > + (set (match_dup 0) > + (plus:SI (match_dup 0) (match_operand:SI 2 "register_operand" ""))) > + (set (match_dup 1) > + (match_dup 0))] > + "TARGET_THUMB1 > + && REGNO_REG_CLASS (REGNO (operands[0])) == HI_REGS" > + [(set (match_dup 1) > + (plus:SI (match_dup 1) (match_dup 2))) > + (set (match_dup 0) (match_dup 1))] ;; likely will be eliminated > + "") > + > +;; case #5: > +;; mov r1, ip > +;; subs r2, r1, r2 > +;; mov ip, r2 # r1 is dead after > +(define_peephole2 > + [(set (match_operand:SI 1 "register_operand" "") > + (match_operand:SI 0 "register_operand" "")) > + (set (match_operand:SI 2 "register_operand" "") > + (minus:SI (match_dup 1) (match_dup 2))) > + (set (match_dup 0) > + (match_dup 2))] > + "TARGET_THUMB1 > + && peep2_reg_dead_p (3, operands[1]) > + && REGNO_REG_CLASS (REGNO (operands[0])) == HI_REGS" > + [(set (match_dup 1) > + (neg:SI (match_dup 2))) > + (set (match_dup 0) > + (plus:SI (match_dup 0) (match_dup 1))) > + (set (match_dup 2) ;; likely will be eliminated > + (match_dup 0))] > + "") > -- > 2.45.2 >
