Message ID | 20211111141020.2738001-7-philipp.tomsich@vrull.eu |
---|---|
State | New |
Headers | show |
Series | Improvements to bitmanip-1.0 (Zb[abcs]) support | expand |
> --- a/gcc/config/riscv/bitmanip.md > +++ b/gcc/config/riscv/bitmanip.md > @@ -367,3 +367,16 @@ (define_insn "*bexti" > "TARGET_ZBS" > "bexti\t%0,%1,%2" > [(set_attr "type" "bitmanip")]) > + > +;; We can create a polarity-reversed mask (i.e. bit N -> { set = 0, clear = -1 }) > +;; using a bext(i) followed by an addi instruction. > +;; This splits the canonical representation of "(a & (1 << BIT_NO)) ? 0 : -1". > +(define_split > + [(set (match_operand:GPR 0 "register_operand") > + (neg:GPR (eq:GPR (zero_extract:GPR (match_operand:GPR 1 "register_operand") > + (const_int 1) > + (match_operand 2)) > + (const_int 0))))] > + "TARGET_ZBB" Should be TARGET_ZBS? > + [(set (match_dup 0) (zero_extract:GPR (match_dup 1) (const_int 1) (match_dup 2))) > + (set (match_dup 0) (plus:GPR (match_dup 0) (const_int -1)))]) > diff --git a/gcc/testsuite/gcc.target/riscv/zbs-bexti.c b/gcc/testsuite/gcc.target/riscv/zbs-bexti.c > new file mode 100644 > index 00000000000..d02c3f7a98d > --- /dev/null > +++ b/gcc/testsuite/gcc.target/riscv/zbs-bexti.c > @@ -0,0 +1,14 @@ > +/* { dg-do compile } */ > +/* { dg-options "-march=rv64gc_zbs -mabi=lp64 -O2" } */ > + > +/* bexti */ > +#define BIT_NO 27 > + > +long > +foo0 (long a) > +{ > + return (a & (1 << BIT_NO)) ? 0 : -1; I got the same code gen for rv64gc_zbs both w/ and w/o this patch, but got better code gen when I changed BIT_NO to 4, so I guess we should use 4 rather than 27 for demonstrating this patch? long foo2 (long a) { return (a & (1 << 4)) ? 0 : -1; }
diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md index 178d1ca0e4b..9e10280e306 100644 --- a/gcc/config/riscv/bitmanip.md +++ b/gcc/config/riscv/bitmanip.md @@ -367,3 +367,16 @@ (define_insn "*bexti" "TARGET_ZBS" "bexti\t%0,%1,%2" [(set_attr "type" "bitmanip")]) + +;; We can create a polarity-reversed mask (i.e. bit N -> { set = 0, clear = -1 }) +;; using a bext(i) followed by an addi instruction. +;; This splits the canonical representation of "(a & (1 << BIT_NO)) ? 0 : -1". +(define_split + [(set (match_operand:GPR 0 "register_operand") + (neg:GPR (eq:GPR (zero_extract:GPR (match_operand:GPR 1 "register_operand") + (const_int 1) + (match_operand 2)) + (const_int 0))))] + "TARGET_ZBB" + [(set (match_dup 0) (zero_extract:GPR (match_dup 1) (const_int 1) (match_dup 2))) + (set (match_dup 0) (plus:GPR (match_dup 0) (const_int -1)))]) diff --git a/gcc/testsuite/gcc.target/riscv/zbs-bexti.c b/gcc/testsuite/gcc.target/riscv/zbs-bexti.c new file mode 100644 index 00000000000..d02c3f7a98d --- /dev/null +++ b/gcc/testsuite/gcc.target/riscv/zbs-bexti.c @@ -0,0 +1,14 @@ +/* { dg-do compile } */ +/* { dg-options "-march=rv64gc_zbs -mabi=lp64 -O2" } */ + +/* bexti */ +#define BIT_NO 27 + +long +foo0 (long a) +{ + return (a & (1 << BIT_NO)) ? 0 : -1; +} + +/* { dg-final { scan-assembler "bexti" } } */ +/* { dg-final { scan-assembler "addi" } } */
Consider creating a polarity-reversed mask from a set-bit (i.e., if the bit is set, produce all-ones; otherwise: all-zeros). Using Zbb, this can be expressed as bexti, followed by an addi of minus-one. To enable the combiner to discover this opportunity, we need to split the canonical expression for "(a & (1 << BIT_NO)) ? 0 : -1" into a form combinable into bexti. Consider the function: long f(long a) { return (a & (1 << BIT_NO)) ? 0 : -1; } This produces the following sequence prior to this change: andi a0,a0,16 seqz a0,a0 neg a0,a0 ret Following this change, it results in: bexti a0,a0,4 addi a0,a0,-1 ret gcc/ChangeLog: * config/riscv/bitmanip.md: Add a splitter to generate polarity-reversed masks from a set bit using bexti + addi. gcc/testsuite/ChangeLog: * gcc.target/riscv/zbs-bexti.c: New test. Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu> --- gcc/config/riscv/bitmanip.md | 13 +++++++++++++ gcc/testsuite/gcc.target/riscv/zbs-bexti.c | 14 ++++++++++++++ 2 files changed, 27 insertions(+) create mode 100644 gcc/testsuite/gcc.target/riscv/zbs-bexti.c