On Fri, Apr 21, 2017 at 09:20:55AM +0100, Kyrill Tkachov wrote: > Hi all, > > Our sub<mode>3_compare1 pattern is not enough to catch cases where we > subtract an immediate and compare against in PARALLEL. This is due to the RTL > canonicalisation rules that require subtractions of immediate IMM be > represented as (plus x -IMM). So we need a bit of trickery to catch those > cases and this patch does that. It adds a new define_insn to match the > plus-negatable-immediate in parallel with a comparison and a peephole that > will bring the two together when possible. Otherwise it's pretty > straightforward. > > The testcase in the patch now generates a single SUBS-immediate instead of a > SUB followed by a CMP. > > Bootstrapped and tested on aarch64-none-linux-gnu. > > Ok for GCC 8?
OK. Thansk, James > > Thanks, > Kyrill > > 2017-04-21 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > > * config/aarch64/aarch64.md (sub<mode>3_compare1_imm): New define_insn. > (peephole2): New peephole2 to emit the above. > * config/aarch64/predicates.md (aarch64_sub_immediate): New predicate. > > 2017-04-21 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > > * gcc.target/aarch64/subs_compare_2.c: New test. > > diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md > index > 2a0341e1a957ebd28bc9e29465803501be23cd72..ff34e0d5ff4713f7b8005855f62e834aceef51f0 > 100644 > --- a/gcc/config/aarch64/aarch64.md > +++ b/gcc/config/aarch64/aarch64.md > @@ -2344,6 +2344,19 @@ (define_insn "sub<mode>3_compare1" > [(set_attr "type" "alus_sreg")] > ) > > +(define_insn "sub<mode>3_compare1_imm" > + [(set (reg:CC CC_REGNUM) > + (compare:CC > + (match_operand:GPI 1 "register_operand" "r") > + (match_operand:GPI 3 "const_int_operand" "n"))) > + (set (match_operand:GPI 0 "register_operand" "=r") > + (plus:GPI (match_dup 1) > + (match_operand:GPI 2 "aarch64_sub_immediate" "J")))] > + "INTVAL (operands[3]) == -INTVAL (operands[2])" > + "subs\\t%<w>0, %<w>1, #%n2" > + [(set_attr "type" "alus_sreg")] > +) > + > (define_peephole2 > [(set (match_operand:GPI 0 "register_operand") > (minus:GPI (match_operand:GPI 1 "aarch64_reg_or_zero") > @@ -2362,6 +2375,24 @@ (define_peephole2 > } > ) > > +(define_peephole2 > + [(set (match_operand:GPI 0 "register_operand") > + (plus:GPI (match_operand:GPI 1 "register_operand") > + (match_operand:GPI 2 "aarch64_sub_immediate"))) > + (set (reg:CC CC_REGNUM) > + (compare:CC > + (match_dup 1) > + (match_operand:GPI 3 "const_int_operand")))] > + "!reg_overlap_mentioned_p (operands[0], operands[1]) > + && INTVAL (operands[3]) == -INTVAL (operands[2])" > + [(const_int 0)] > + { > + emit_insn (gen_sub<mode>3_compare1_imm (operands[0], operands[1], > + operands[2], operands[3])); > + DONE; > + } > +) > + > (define_insn "*sub_<shift>_<mode>" > [(set (match_operand:GPI 0 "register_operand" "=r") > (minus:GPI (match_operand:GPI 3 "register_operand" "r") > diff --git a/gcc/config/aarch64/predicates.md > b/gcc/config/aarch64/predicates.md > index > 875ae6180e232e25b29c8787c0acf7a5dfa82d94..4bd8f45562c017bca736ae466ede6b9e4de0d17a > 100644 > --- a/gcc/config/aarch64/predicates.md > +++ b/gcc/config/aarch64/predicates.md > @@ -77,6 +77,10 @@ (define_predicate "aarch64_fp_pow2" > (define_predicate "aarch64_fp_vec_pow2" > (match_test "aarch64_vec_fpconst_pow_of_2 (op) > 0")) > > +(define_predicate "aarch64_sub_immediate" > + (and (match_code "const_int") > + (match_test "aarch64_uimm12_shift (-INTVAL (op))"))) > + > (define_predicate "aarch64_plus_immediate" > (and (match_code "const_int") > (ior (match_test "aarch64_uimm12_shift (INTVAL (op))") > diff --git a/gcc/testsuite/gcc.target/aarch64/subs_compare_2.c > b/gcc/testsuite/gcc.target/aarch64/subs_compare_2.c > new file mode 100644 > index > 0000000000000000000000000000000000000000..60c6d9e5ccd8fce42c388c831a8060dead128491 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/aarch64/subs_compare_2.c > @@ -0,0 +1,15 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2" } */ > + > +int > +foo (int a, int b) > +{ > + int x = a - 4; > + if (a < 4) > + return x; > + else > + return 0; > +} > + > +/* { dg-final { scan-assembler-times "subs\\tw\[0-9\]+, w\[0-9\]+, #4" 1 } } > */ > +/* { dg-final { scan-assembler-not "cmp\\tw\[0-9\]+, w\[0-9\]+" } } */