[gcc(refs/vendors/vrull/heads/for-upstream)] RISC-V: No extensions for SImode min/max against safe constant

[Philipp Tomsich <ptomsich@gcc.gnu.org>]

https://gcc.gnu.org/g:37db290428213b7ce14fb838262af7675aac20ae

commit 37db290428213b7ce14fb838262af7675aac20ae
Author: Philipp Tomsich <philipp.tomsich@vrull.eu>
Date:   Sun Oct 16 10:51:47 2022 +0200

    RISC-V: No extensions for SImode min/max against safe constant
    
    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.
    
    Series-version: 2
    
    Series-changes: 2
    - fixes the use minmax_optab (was: bitmanip_optab), which didn't get
      applied to the cherry-pick on the previous submission
    
    Series-to: gcc-patches@gcc.gnu.org
    Series-cc: Palmer Dabbelt <palmer@rivosinc.com>
    Series-cc: Vineet Gupta <vineetg@rivosinc.com>
    Series-cc: Christoph Muellner <christoph.muellner@vrull.eu>
    Series-cc: Kito Cheng <kito.cheng@gmail.com>
    Series-cc: Jeff Law <jlaw@ventanamicro.com>

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

diff --git a/gcc/config/riscv/bitmanip.md b/gcc/config/riscv/bitmanip.md
index a545cd3f82b..8b6a7cad3f6 100644
--- a/gcc/config/riscv/bitmanip.md
+++ b/gcc/config/riscv/bitmanip.md
@@ -368,6 +368,24 @@
   "<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" } } */
+