Kito, Did you have a chance to take a look at this one?
I assume this will have to wait until we reopen for 13... OK for 13? Also: OK for a backport (once a branch for that exists)? Philipp. On Sun, 24 Apr 2022 at 01:44, Philipp Tomsich <philipp.toms...@vrull.eu> wrote: > > The Zbb support has introduced ctz and clz to the backend, but some > transformations in GCC need to know what the value of c[lt]z at zero > is. This affects how the optab is generated and may suppress use of > CLZ/CTZ in tree passes. > > Among other things, this is needed for the transformation of > table-based ctz-implementations, such as in deepsjeng, to work > (see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90838). > > Prior to this change, the test case from PR90838 would compile to > on RISC-V targets with Zbb: > myctz: > lui a4,%hi(.LC0) > ld a4,%lo(.LC0)(a4) > neg a5,a0 > and a5,a5,a0 > mul a5,a5,a4 > lui a4,%hi(.LANCHOR0) > addi a4,a4,%lo(.LANCHOR0) > srli a5,a5,58 > sh2add a5,a5,a4 > lw a0,0(a5) > ret > > After this change, we get: > myctz: > ctz a0,a0 > andi a0,a0,63 > ret > > Testing this with deepsjeng_r (from SPEC 2017) against QEMU, this > shows a clear reduction in dynamic instruction count: > - before 1961888067076 > - after 1907928279874 (2.75% reduction) > > gcc/ChangeLog: > > * config/riscv/riscv.h (CLZ_DEFINED_VALUE_AT_ZERO): Implement. > (CTZ_DEFINED_VALUE_AT_ZERO): Same. > > gcc/testsuite/ChangeLog: > > * gcc.dg/pr90838.c: Add additional flags (dg-additional-options) > when compiling for riscv64. > * gcc.target/riscv/zbb-ctz.c: New test. > > Signed-off-by: Philipp Tomsich <philipp.toms...@vrull.eu> > Signed-off-by: Manolis Tsamis <manolis.tsa...@vrull.eu> > Co-developed-by: Manolis Tsamis <manolis.tsa...@vrull.eu> > > --- > gcc/config/riscv/riscv.h | 5 ++ > gcc/testsuite/gcc.dg/pr90838.c | 2 + > gcc/testsuite/gcc.target/riscv/zbb-ctz-32.c | 65 ++++++++++++++++++++ > gcc/testsuite/gcc.target/riscv/zbb-ctz.c | 66 +++++++++++++++++++++ > 4 files changed, 138 insertions(+) > create mode 100644 gcc/testsuite/gcc.target/riscv/zbb-ctz-32.c > create mode 100644 gcc/testsuite/gcc.target/riscv/zbb-ctz.c > > diff --git a/gcc/config/riscv/riscv.h b/gcc/config/riscv/riscv.h > index 4210e252255..95f72e2fd3f 100644 > --- a/gcc/config/riscv/riscv.h > +++ b/gcc/config/riscv/riscv.h > @@ -1019,4 +1019,9 @@ extern void riscv_remove_unneeded_save_restore_calls > (void); > > #define HARD_REGNO_RENAME_OK(FROM, TO) riscv_hard_regno_rename_ok (FROM, TO) > > +#define CLZ_DEFINED_VALUE_AT_ZERO(MODE, VALUE) \ > + ((VALUE) = GET_MODE_UNIT_BITSIZE (MODE), 2) > +#define CTZ_DEFINED_VALUE_AT_ZERO(MODE, VALUE) \ > + ((VALUE) = GET_MODE_UNIT_BITSIZE (MODE), 2) > + > #endif /* ! GCC_RISCV_H */ > diff --git a/gcc/testsuite/gcc.dg/pr90838.c b/gcc/testsuite/gcc.dg/pr90838.c > index 41c5dab9a5c..162bd6f51d0 100644 > --- a/gcc/testsuite/gcc.dg/pr90838.c > +++ b/gcc/testsuite/gcc.dg/pr90838.c > @@ -1,5 +1,6 @@ > /* { dg-do compile } */ > /* { dg-options "-O2 -fdump-tree-forwprop2-details" } */ > +/* { dg-additional-options "-march=rv64gc_zbb" { target riscv64*-*-* } } */ > > int ctz1 (unsigned x) > { > @@ -57,3 +58,4 @@ int ctz4 (unsigned long x) > } > > /* { dg-final { scan-tree-dump-times {= \.CTZ} 4 "forwprop2" { target > aarch64*-*-* } } } */ > +/* { dg-final { scan-tree-dump-times {= \.CTZ} 4 "forwprop2" { target > riscv64*-*-* } } } */ > diff --git a/gcc/testsuite/gcc.target/riscv/zbb-ctz-32.c > b/gcc/testsuite/gcc.target/riscv/zbb-ctz-32.c > new file mode 100644 > index 00000000000..b903517197a > --- /dev/null > +++ b/gcc/testsuite/gcc.target/riscv/zbb-ctz-32.c > @@ -0,0 +1,65 @@ > +/* { dg-do compile } */ > +/* { dg-options "-march=rv32gc_zbb -mabi=ilp32" } */ > +/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" } } */ > + > +int ctz1 (unsigned x) > +{ > + static const char table[32] = > + { > + 0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8, > + 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9 > + }; > + > + return table[((unsigned)((x & -x) * 0x077CB531U)) >> 27]; > +} > + > +int ctz2 (unsigned x) > +{ > +#define u 0 > + static short table[64] = > + { > + 32, 0, 1,12, 2, 6, u,13, 3, u, 7, u, u, u, u,14, > + 10, 4, u, u, 8, u, u,25, u, u, u, u, u,21,27,15, > + 31,11, 5, u, u, u, u, u, 9, u, u,24, u, u,20,26, > + 30, u, u, u, u,23, u,19,29, u,22,18,28,17,16, u > + }; > + > + x = (x & -x) * 0x0450FBAF; > + return table[x >> 26]; > +} > + > +int ctz3 (unsigned x) > +{ > + static int table[32] = > + { > + 0, 1, 2,24, 3,19, 6,25, 22, 4,20,10,16, 7,12,26, > + 31,23,18, 5,21, 9,15,11,30,17, 8,14,29,13,28,27 > + }; > + > + if (x == 0) return 32; > + x = (x & -x) * 0x04D7651F; > + return table[x >> 27]; > +} > + > +static const unsigned long long magic = 0x03f08c5392f756cdULL; > + > +static const char table[64] = { > + 0, 1, 12, 2, 13, 22, 17, 3, > + 14, 33, 23, 36, 18, 58, 28, 4, > + 62, 15, 34, 26, 24, 48, 50, 37, > + 19, 55, 59, 52, 29, 44, 39, 5, > + 63, 11, 21, 16, 32, 35, 57, 27, > + 61, 25, 47, 49, 54, 51, 43, 38, > + 10, 20, 31, 56, 60, 46, 53, 42, > + 9, 30, 45, 41, 8, 40, 7, 6, > +}; > + > +int ctz4 (unsigned long x) > +{ > + unsigned long lsb = x & -x; > + return table[(lsb * magic) >> 58]; > +} > + > +/* { dg-final { scan-assembler-times "ctz\t" 3 } } */ > +/* { dg-final { scan-assembler-times "andi\t" 1 } } */ > +/* { dg-final { scan-assembler-times "mul\t" 1 } } */ > diff --git a/gcc/testsuite/gcc.target/riscv/zbb-ctz.c > b/gcc/testsuite/gcc.target/riscv/zbb-ctz.c > new file mode 100644 > index 00000000000..f9fbcb38dee > --- /dev/null > +++ b/gcc/testsuite/gcc.target/riscv/zbb-ctz.c > @@ -0,0 +1,66 @@ > +/* { dg-do compile } */ > +/* { dg-options "-march=rv64gc_zbb -mabi=lp64" } */ > +/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" } } */ > + > +int ctz1 (unsigned x) > +{ > + static const char table[32] = > + { > + 0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8, > + 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9 > + }; > + > + return table[((unsigned)((x & -x) * 0x077CB531U)) >> 27]; > +} > + > +int ctz2 (unsigned x) > +{ > +#define u 0 > + static short table[64] = > + { > + 32, 0, 1,12, 2, 6, u,13, 3, u, 7, u, u, u, u,14, > + 10, 4, u, u, 8, u, u,25, u, u, u, u, u,21,27,15, > + 31,11, 5, u, u, u, u, u, 9, u, u,24, u, u,20,26, > + 30, u, u, u, u,23, u,19,29, u,22,18,28,17,16, u > + }; > + > + x = (x & -x) * 0x0450FBAF; > + return table[x >> 26]; > +} > + > +int ctz3 (unsigned x) > +{ > + static int table[32] = > + { > + 0, 1, 2,24, 3,19, 6,25, 22, 4,20,10,16, 7,12,26, > + 31,23,18, 5,21, 9,15,11,30,17, 8,14,29,13,28,27 > + }; > + > + if (x == 0) return 32; > + x = (x & -x) * 0x04D7651F; > + return table[x >> 27]; > +} > + > +static const unsigned long long magic = 0x03f08c5392f756cdULL; > + > +static const char table[64] = { > + 0, 1, 12, 2, 13, 22, 17, 3, > + 14, 33, 23, 36, 18, 58, 28, 4, > + 62, 15, 34, 26, 24, 48, 50, 37, > + 19, 55, 59, 52, 29, 44, 39, 5, > + 63, 11, 21, 16, 32, 35, 57, 27, > + 61, 25, 47, 49, 54, 51, 43, 38, > + 10, 20, 31, 56, 60, 46, 53, 42, > + 9, 30, 45, 41, 8, 40, 7, 6, > +}; > + > +int ctz4 (unsigned long x) > +{ > + unsigned long lsb = x & -x; > + return table[(lsb * magic) >> 58]; > +} > + > +/* { dg-final { scan-assembler-times "ctzw\t" 3 } } */ > +/* { dg-final { scan-assembler-times "ctz\t" 1 } } */ > +/* { dg-final { scan-assembler-times "andi\t" 2 } } */ > +/* { dg-final { scan-assembler-not "mul" } } */ > -- > 2.34.1 >
