[gcc r12-4657] RISC-V: Use li and rori to load constants.

[Kito Cheng <kito@gcc.gnu.org>]

https://gcc.gnu.org/g:26d2818bb73a09622f87df53d6280d18b229bcbc

commit r12-4657-g26d2818bb73a09622f87df53d6280d18b229bcbc
Author: Jim Wilson <jimw@sifive.com>
Date:   Sat Oct 31 11:41:19 2020 -0700

    RISC-V: Use li and rori to load constants.
    
    gcc/ChangeLog:
    
            * config/riscv/riscv.c (riscv_build_integer_1): Build integer
            with rotate.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/riscv/zbb-li-rotr.c: New.

Diff:
---
 gcc/config/riscv/riscv.c                     | 41 ++++++++++++++++++++++++++++
 gcc/testsuite/gcc.target/riscv/zbb-li-rotr.c | 35 ++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/gcc/config/riscv/riscv.c b/gcc/config/riscv/riscv.c
index cb93e3fb88a..3ed34f234e5 100644
--- a/gcc/config/riscv/riscv.c
+++ b/gcc/config/riscv/riscv.c
@@ -462,6 +462,47 @@ riscv_build_integer_1 (struct riscv_integer_op codes[RISCV_MAX_INTEGER_OPS],
 	}
     }
 
+  if (cost > 2 && TARGET_64BIT && TARGET_ZBB)
+    {
+      int leading_ones = clz_hwi (~value);
+      int trailing_ones = ctz_hwi (~value);
+
+      /* If all bits are one except a few that are zero, and the zero bits
+	 are within a range of 11 bits, and at least one of the upper 32-bits
+	 is a zero, then we can generate a constant by loading a small
+	 negative constant and rotating.  */
+      if (leading_ones < 32
+	  && ((64 - leading_ones - trailing_ones) < 12))
+	{
+	  codes[0].code = UNKNOWN;
+	  /* The sign-bit might be zero, so just rotate to be safe.  */
+	  codes[0].value = (((unsigned HOST_WIDE_INT) value >> trailing_ones)
+			    | (value << (64 - trailing_ones)));
+	  codes[1].code = ROTATERT;
+	  codes[1].value = 64 - trailing_ones;
+	  cost = 2;
+	}
+      /* Handle the case where the 11 bit range of zero bits wraps around.  */
+      else
+	{
+	  int upper_trailing_ones = ctz_hwi (~value >> 32);
+	  int lower_leading_ones = clz_hwi (~value << 32);
+
+	  if (upper_trailing_ones < 32 && lower_leading_ones < 32
+	      && ((64 - upper_trailing_ones - lower_leading_ones) < 12))
+	    {
+	      codes[0].code = UNKNOWN;
+	      /* The sign-bit might be zero, so just rotate to be safe.  */
+	      codes[0].value = ((value << (32 - upper_trailing_ones))
+				| ((unsigned HOST_WIDE_INT) value
+				   >> (32 + upper_trailing_ones)));
+	      codes[1].code = ROTATERT;
+	      codes[1].value = 32 - upper_trailing_ones;
+	      cost = 2;
+	    }
+	}
+    }
+
   gcc_assert (cost <= RISCV_MAX_INTEGER_OPS);
   return cost;
 }
diff --git a/gcc/testsuite/gcc.target/riscv/zbb-li-rotr.c b/gcc/testsuite/gcc.target/riscv/zbb-li-rotr.c
new file mode 100644
index 00000000000..03254ed9150
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/zbb-li-rotr.c
@@ -0,0 +1,35 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gc_zbb -mabi=lp64 -O2" } */
+
+long
+li_rori (void)
+{
+  return 0xffff77ffffffffffL;
+}
+
+long
+li_rori_2 (void)
+{
+  return 0x77ffffffffffffffL;
+}
+
+long
+li_rori_3 (void)
+{
+  return 0xfffffffeefffffffL;
+}
+
+long
+li_rori_4 (void)
+{
+  return 0x5ffffffffffffff5L;
+}
+
+long
+li_rori_5 (void)
+{
+  return 0xaffffffffffffffaL;
+}
+
+
+/* { dg-final { scan-assembler-times "rori\t" 5 } } */