[PATCH v2] RISC-V: No extensions for SImode min/max against safe constant

[PATCH v2] RISC-V: No extensions for SImode min/max against safe constant

[Philipp Tomsich]

Optimize the common case of a SImode min/max against a constant
that is safe both for sign- and zero-extension.
E.g., consider the case
  int f(unsigned int* a)
  {
    const int C = 1000;
    return *a * 3 > C ? C : *a * 3;
  }
where the constant C will yield the same result in DImode whether
sign- or zero-extended.

This should eventually go away once the lowering to RTL smartens up
and considers the precision/signedness and the value-ranges of the
operands to MIN_EXPR nad MAX_EXPR.

gcc/ChangeLog:

	* config/riscv/bitmanip.md (*minmax): Additional pattern for
          min/max against constants that are extension-invariant.
	* config/riscv/iterators.md (minmax_optab): Add an iterator
	  that has only min and max rtl.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/zbb-min-max-02.c: New test.

Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
---

Changes in v2:

- fixes the use of minmax_optab (was: bitmanip_optab), which is a
  change that dropped off the cherry-pick on the previous submission

 gcc/config/riscv/bitmanip.md                   | 18 ++++++++++++++++++
 gcc/config/riscv/iterators.md                  |  4 ++++
 .../gcc.target/riscv/zbb-min-max-02.c          | 14 ++++++++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/riscv/zbb-min-max-02.c

diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
index dddd3422c43..bb23ceb86d9 100644
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -360,6 +360,24 @@
   "<bitmanip_insn>\t%0,%1,%2"
   [(set_attr "type" "bitmanip")])
 
+;; Optimize the common case of a SImode min/max against a constant
+;; that is safe both for sign- and zero-extension.
+(define_insn_and_split "*minmax"
+  [(set (match_operand:DI 0 "register_operand" "=r")
+	(sign_extend:DI
+	  (subreg:SI
+	    (bitmanip_minmax:DI (zero_extend:DI (match_operand:SI 1 "register_operand" "r"))
+						(match_operand:DI 2 "immediate_operand" "i"))
+	   0)))
+   (clobber (match_scratch:DI 3 "=&r"))
+   (clobber (match_scratch:DI 4 "=&r"))]
+  "TARGET_64BIT && TARGET_ZBB && sext_hwi (INTVAL (operands[2]), 32) >= 0"
+  "#"
+  "&& reload_completed"
+  [(set (match_dup 3) (sign_extend:DI (match_dup 1)))
+   (set (match_dup 4) (match_dup 2))
+   (set (match_dup 0) (<minmax_optab>:DI (match_dup 3) (match_dup 4)))])
+
 ;; ZBS extension.
 
 (define_insn "*bset<mode>"
diff --git a/gcc/config/riscv/iterators.md b/gcc/config/riscv/iterators.md
index 50380ecfac9..cbbf61f6514 100644
--- a/gcc/config/riscv/iterators.md
+++ b/gcc/config/riscv/iterators.md
@@ -213,6 +213,10 @@
   [(plus "add") (ior "or") (xor "xor") (and "and")])
 
 ; bitmanip code attributes
+(define_code_attr minmax_optab [(smin "smin")
+				(smax "smax")
+				(umin "umin")
+				(umax "umax")])
 (define_code_attr bitmanip_optab [(smin "smin")
 				  (smax "smax")
 				  (umin "umin")
diff --git a/gcc/testsuite/gcc.target/riscv/zbb-min-max-02.c b/gcc/testsuite/gcc.target/riscv/zbb-min-max-02.c
new file mode 100644
index 00000000000..b462859f10f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zbb-min-max-02.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zba_zbb -mabi=lp64" } */
+/* { dg-skip-if "" { *-*-* } { "-O0" "-O1" "-Os" "-Oz" "-Og" } } */
+
+int f(unsigned int* a)
+{
+  const int C = 1000;
+  return *a * 3 > C ? C : *a * 3;
+}
+
+/* { dg-final { scan-assembler-times "minu" 1 } } */
+/* { dg-final { scan-assembler-times "sext.w" 1 } } */
+/* { dg-final { scan-assembler-not "zext.w" } } */
+
-- 
2.34.1

Re: [PATCH v2] RISC-V: No extensions for SImode min/max against safe constant

[Jeff Law]

On 11/8/22 17:06, Philipp Tomsich wrote:
> Optimize the common case of a SImode min/max against a constant
> that is safe both for sign- and zero-extension.
> E.g., consider the case
>    int f(unsigned int* a)
>    {
>      const int C = 1000;
>      return *a * 3 > C ? C : *a * 3;
>    }
> where the constant C will yield the same result in DImode whether
> sign- or zero-extended.
>
> This should eventually go away once the lowering to RTL smartens up
> and considers the precision/signedness and the value-ranges of the
> operands to MIN_EXPR nad MAX_EXPR.
>
> gcc/ChangeLog:
>
> 	* config/riscv/bitmanip.md (*minmax): Additional pattern for
>            min/max against constants that are extension-invariant.
> 	* config/riscv/iterators.md (minmax_optab): Add an iterator
> 	  that has only min and max rtl.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.target/riscv/zbb-min-max-02.c: New test.

Ok

jeff

Re: [PATCH v2] RISC-V: No extensions for SImode min/max against safe constant

[Philipp Tomsich]

[-- Attachment #1: Type: text/plain, Size: 1103 bytes --]

Applied to master. Thanks!
--Philipp.

On Fri, 18 Nov 2022 at 21:11, Jeff Law <jeffreyalaw@gmail.com> wrote:

>
> On 11/8/22 17:06, Philipp Tomsich wrote:
> > Optimize the common case of a SImode min/max against a constant
> > that is safe both for sign- and zero-extension.
> > E.g., consider the case
> >    int f(unsigned int* a)
> >    {
> >      const int C = 1000;
> >      return *a * 3 > C ? C : *a * 3;
> >    }
> > where the constant C will yield the same result in DImode whether
> > sign- or zero-extended.
> >
> > This should eventually go away once the lowering to RTL smartens up
> > and considers the precision/signedness and the value-ranges of the
> > operands to MIN_EXPR nad MAX_EXPR.
> >
> > gcc/ChangeLog:
> >
> >       * config/riscv/bitmanip.md (*minmax): Additional pattern for
> >            min/max against constants that are extension-invariant.
> >       * config/riscv/iterators.md (minmax_optab): Add an iterator
> >         that has only min and max rtl.
> >
> > gcc/testsuite/ChangeLog:
> >
> >       * gcc.target/riscv/zbb-min-max-02.c: New test.
>
> Ok
>
> jeff
>
>
>