Hi!
On Mon, 8 Jul 2024 at 10:57, Siarhei Volkau <lis8...@gmail.com> wrote: > > 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 Why replace 'add' with 'adds' ? Thanks, Christophe > > > > 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 > >
