Thanks Tamar for comments.
The :s flag is somehow ignored in matching according the gccint doc.
"The second supported flag is s which tells the code generator to fail the
pattern if the
expression marked with s does have more than one use and the simplification
results in an
expression with more than one operator."
I also diff the generated code in gimple_unsigned_integer_sat_trunc, it doesn't
have single use when :s flag.
&& TYPE_UNSIGNED (TREE_TYPE (captures[0]))
// the :s flag
&& TYPE_UNSIGNED (TREE_TYPE (captures[0])) && single_use (captures[1]) //
explicit single_use check.
Pan
-----Original Message-----
From: Tamar Christina <tamar.christ...@arm.com>
Sent: Thursday, July 18, 2024 8:36 PM
To: Li, Pan2 <pan2...@intel.com>; gcc-patches@gcc.gnu.org
Cc: juzhe.zh...@rivai.ai; kito.ch...@gmail.com; richard.guent...@gmail.com;
jeffreya...@gmail.com; rdapp....@gmail.com; Liu, Hongtao <hongtao....@intel.com>
Subject: RE: [PATCH v1] Match: Only allow single use of MIN_EXPR for SAT_TRUNC
form 2 [PR115863]
> -----Original Message-----
> From: pan2...@intel.com <pan2...@intel.com>
> Sent: Thursday, July 18, 2024 1:27 PM
> To: gcc-patches@gcc.gnu.org
> Cc: juzhe.zh...@rivai.ai; kito.ch...@gmail.com; richard.guent...@gmail.com;
> Tamar Christina <tamar.christ...@arm.com>; jeffreya...@gmail.com;
> rdapp....@gmail.com; hongtao....@intel.com; Pan Li <pan2...@intel.com>
> Subject: [PATCH v1] Match: Only allow single use of MIN_EXPR for SAT_TRUNC
> form 2 [PR115863]
>
> From: Pan Li <pan2...@intel.com>
>
> The SAT_TRUNC form 2 has below pattern matching.
> From:
> _18 = MIN_EXPR <left_8, 4294967295>;
> iftmp.0_11 = (unsigned int) _18;
>
> To:
> _18 = MIN_EXPR <left_8, 4294967295>;
> iftmp.0_11 = .SAT_TRUNC (_18);
>
> But if there is another use of _18 like below, the transform to the
> .SAT_TRUNC may have no earnings. For example:
>
> From:
> _18 = MIN_EXPR <left_8, 4294967295>; // op_0 def
> iftmp.0_11 = (unsigned int) _18; // op_0
> stream.avail_out = iftmp.0_11;
> left_37 = left_8 - _18; // op_0 use
>
> To:
> _18 = MIN_EXPR <left_8, 4294967295>; // op_0 def
> iftmp.0_11 = .SAT_TRUNC (_18);
> stream.avail_out = iftmp.0_11;
> left_37 = left_8 - _18; // op_0 use
>
> Pattern recog to .SAT_TRUNC cannot eliminate MIN_EXPR as above. Then the
> backend (for example x86/riscv) will have additional 2-3 more insns
> after pattern recog besides the MIN_EXPR. Thus, keep the normal truncation
> as is should be the better choose.
>
> The below testsuites are passed for this patch:
> 1. The rv64gcv fully regression tests.
> 2. The x86 bootstrap tests.
> 3. The x86 fully regression tests.
>
> PR target/115863
>
> gcc/ChangeLog:
>
> * match.pd: Add single_use of MIN_EXPR for .SAT_TRUNC form 2.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/i386/pr115863-1.c: New test.
>
> Signed-off-by: Pan Li <pan2...@intel.com>
> ---
> gcc/match.pd | 15 +++++++--
> gcc/testsuite/gcc.target/i386/pr115863-1.c | 37 ++++++++++++++++++++++
> 2 files changed, 50 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/pr115863-1.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 5cb399b8718..d4f040b5c7b 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -3252,10 +3252,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>
> /* Unsigned saturation truncate, case 2, sizeof (WT) > sizeof (NT).
> SAT_U_TRUNC = (NT)(MIN_EXPR (X, 255)). */
> +/* If Op_0 def is MIN_EXPR and not single_use. Aka below pattern:
> +
> + _18 = MIN_EXPR <left_8, 4294967295>; // op_0 def
> + iftmp.0_11 = (unsigned int) _18; // op_0
> + stream.avail_out = iftmp.0_11;
> + left_37 = left_8 - _18; // op_0 use
> +
> + Transfer to .SAT_TRUNC will have MIN_EXPR still live. Then the backend
> + (for example x86/riscv) will have 2-3 more insns generation for .SAT_TRUNC
> + besides the MIN_EXPR. Thus, keep the normal truncation as is should be
> + the better choose. */
> (match (unsigned_integer_sat_trunc @0)
> - (convert (min @0 INTEGER_CST@1))
> + (convert (min@2 @0 INTEGER_CST@1))
> (if (INTEGRAL_TYPE_P (type) && TYPE_UNSIGNED (type)
> - && TYPE_UNSIGNED (TREE_TYPE (@0)))
> + && TYPE_UNSIGNED (TREE_TYPE (@0)) && single_use (@2))
You can probably use the single use flag here? so
> - (convert (min @0 INTEGER_CST@1))
> + (convert (min:s @0 @0 INTEGER_CST@1))
?
Cheers,
Tamar
> (with
> {
> unsigned itype_precision = TYPE_PRECISION (TREE_TYPE (@0));
> diff --git a/gcc/testsuite/gcc.target/i386/pr115863-1.c
> b/gcc/testsuite/gcc.target/i386/pr115863-1.c
> new file mode 100644
> index 00000000000..a672f62cec5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr115863-1.c
> @@ -0,0 +1,37 @@
> +/* PR target/115863 */
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -fdump-rtl-expand-details" } */
> +
> +#include <stdint-gcc.h>
> +
> +typedef struct z_stream_s {
> + uint32_t avail_out;
> +} z_stream;
> +
> +typedef z_stream *z_streamp;
> +
> +extern int deflate (z_streamp strmp);
> +
> +int compress2 (uint64_t *destLen)
> +{
> + z_stream stream;
> + int err;
> + const uint32_t max = (uint32_t)(-1);
> + uint64_t left;
> +
> + left = *destLen;
> +
> + stream.avail_out = 0;
> +
> + do {
> + if (stream.avail_out == 0) {
> + stream.avail_out = left > (uint64_t)max ? max : (uint32_t)left;
> + left -= stream.avail_out;
> + }
> + err = deflate(&stream);
> + } while (err == 0);
> +
> + return err;
> +}
> +
> +/* { dg-final { scan-rtl-dump-not ".SAT_TRUNC " "expand" } } */
> --
> 2.34.1
