[PATCH v1] RISC-V: Support XVentanaCondOps extension

Philipp Tomsich philipp.tomsich@vrull.eu
Sun Jan 9 19:29:48 GMT 2022 

Ventana Micro has published the specification for their
XVentanaCondOps ("conditional ops") extension at
  https://github.com/ventanamicro/ventana-custom-extensions/releases/download/v1.0.0/ventana-custom-extensions-v1.0.0.pdf
which contains two new instructions
  - vt.maskc
  - vt.maskcn
that can be used in constructing branchless sequences for
various conditional-arithmetic, conditional-logical, and
conditional-select operations.

To support such vendor-defined instructions in the mainline binutils,
this change also adds a riscv_supported_vendor_x_ext secondary
dispatch table (but also keeps the behaviour of allowing any unknow
X-extension to be specified in addition to the known ones from this
table).

As discussed, this change already includes the planned/agreed future
requirements for X-extensions (which are likely to be captured in the
riscv-toolchain-conventions repository):
  - a public specification document is available (see above) and is
    referenced from the gas-documentation
  - the naming follows chapter 27 of the RISC-V ISA specification
  - instructions are prefixed by a vendor-prefix (vt for Ventana)
    to ensure that they neither conflict with future standard
    extensions nor clash with other vendors

bfd/ChangeLog:

	* elfxx-riscv.c (riscv_get_default_ext_version): Add riscv_supported_vendor_x_ext.
	(riscv_multi_subset_supports): Recognize INSN_CLASS_XVENTANACONDOPS.

gas/ChangeLog:

	* doc/c-riscv.texi: Add section to list custom extensions and
          their documentation URLs.
	* testsuite/gas/riscv/x-ventana-condops.d: New test.
	* testsuite/gas/riscv/x-ventana-condops.s: New test.

include/ChangeLog:

	* opcode/riscv-opc.h Add vt.maskc and vt.maskcn.
	* opcode/riscv.h (enum riscv_insn_class): Add INSN_CLASS_XVENTANACONDOPS.

opcodes/ChangeLog:

	* riscv-opc.c: Add vt.maskc and vt.maskcn.

---

 bfd/elfxx-riscv.c                           | 13 +++++++++++--
 gas/doc/c-riscv.texi                        | 20 ++++++++++++++++++++
 gas/testsuite/gas/riscv/x-ventana-condops.d | 12 ++++++++++++
 gas/testsuite/gas/riscv/x-ventana-condops.s |  4 ++++
 include/opcode/riscv-opc.h                  |  7 +++++++
 include/opcode/riscv.h                      |  1 +
 opcodes/riscv-opc.c                         |  4 ++++
 7 files changed, 59 insertions(+), 2 deletions(-)
 create mode 100644 gas/testsuite/gas/riscv/x-ventana-condops.d
 create mode 100644 gas/testsuite/gas/riscv/x-ventana-condops.s

diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
index 8409c0254e5..39fc1e9911b 100644
--- a/bfd/elfxx-riscv.c
+++ b/bfd/elfxx-riscv.c
@@ -1241,6 +1241,13 @@ static struct riscv_supported_ext riscv_supported_std_zxm_ext[] =
   {NULL, 0, 0, 0, 0}
 };
 
+static struct riscv_supported_ext riscv_supported_vendor_x_ext[] =
+{
+  /* XVentanaCondOps: https://github.com/ventanamicro/ventana-custom-extensions/releases/download/v1.0.0/ventana-custom-extensions-v1.0.0.pdf */
+  {"xventanacondops",	ISA_SPEC_CLASS_DRAFT,	1, 0, 0 },
+  {NULL, 0, 0, 0, 0}
+};
+
 const struct riscv_supported_ext *riscv_all_supported_ext[] =
 {
   riscv_supported_std_ext,
@@ -1248,6 +1255,7 @@ const struct riscv_supported_ext *riscv_all_supported_ext[] =
   riscv_supported_std_s_ext,
   riscv_supported_std_h_ext,
   riscv_supported_std_zxm_ext,
+  riscv_supported_vendor_x_ext,
   NULL
 };
 
@@ -1513,8 +1521,7 @@ riscv_get_default_ext_version (enum riscv_spec_class *default_isa_spec,
     case RV_ISA_CLASS_Z: table = riscv_supported_std_z_ext; break;
     case RV_ISA_CLASS_S: table = riscv_supported_std_s_ext; break;
     case RV_ISA_CLASS_H: table = riscv_supported_std_h_ext; break;
-    case RV_ISA_CLASS_X:
-      break;
+    case RV_ISA_CLASS_X: table = riscv_supported_vendor_x_ext; break;
     default:
       table = riscv_supported_std_ext;
     }
@@ -2406,6 +2413,8 @@ riscv_multi_subset_supports (riscv_parse_subset_t *rps,
 	      || riscv_subset_supports (rps, "zve32f"));
     case INSN_CLASS_SVINVAL:
       return riscv_subset_supports (rps, "svinval");
+    case INSN_CLASS_XVENTANACONDOPS:
+      return riscv_subset_supports (rps, "xventanacondops");
     default:
       rps->error_handler
         (_("internal: unreachable INSN_CLASS_*"));
diff --git a/gas/doc/c-riscv.texi b/gas/doc/c-riscv.texi
index be9c1148355..1e24053cbdc 100644
--- a/gas/doc/c-riscv.texi
+++ b/gas/doc/c-riscv.texi
@@ -20,6 +20,7 @@
 * RISC-V-Modifiers::      RISC-V Assembler Modifiers
 * RISC-V-Formats::        RISC-V Instruction Formats
 * RISC-V-ATTRIBUTE::      RISC-V Object Attribute
+* RISC-V-CustomExts::     RISC-V Custom (Vendor-Defined) Extensions
 @end menu
 
 @node RISC-V-Options
@@ -692,3 +693,22 @@ the privileged specification.  It will report errors if object files of
 different privileged specification versions are merged.
 
 @end table
+
+@node RISC-V-CustomExts
+@section RISC-V Custom (Vendor-Defined) Extensions
+@cindex custom (vendor-defined) extensions, RISC-V
+@cindex RISC-V custom (vendor-defined) extensions
+
+The following table lists the custom (vendor-defined) RISC-V
+extensions supported and provides the location of their
+publicly-released documentation:
+
+@table @r
+@item XVentanaCondOps
+XVentanaCondOps extension provides instructions for branchless
+sequences that perform conditional arithmetic, conditional
+bitwise-logic, and conditional select operations.
+
+It is documented at @url{https://github.com/ventanamicro/ventana-custom-extensions/releases/download/v1.0.0/ventana-custom-extensions-v1.0.0.pdf}.
+
+@end table
diff --git a/gas/testsuite/gas/riscv/x-ventana-condops.d b/gas/testsuite/gas/riscv/x-ventana-condops.d
new file mode 100644
index 00000000000..cab0cc8dc12
--- /dev/null
+++ b/gas/testsuite/gas/riscv/x-ventana-condops.d
@@ -0,0 +1,12 @@
+#as: -march=rv64i_xventanacondops1p0
+#source: x-ventana-condops.s
+#objdump: -d
+
+.*:[ 	]+file format .*
+
+
+Disassembly of section .text:
+
+0+000 <target>:
+[ 	]+0:[ 	]+00c5e57b[ 	]+vt.maskc[ 	]+a0,a1,a2
+[ 	]+4:[ 	]+00e6f57b[ 	]+vt.maskcn[ 	]+a0,a3,a4
diff --git a/gas/testsuite/gas/riscv/x-ventana-condops.s b/gas/testsuite/gas/riscv/x-ventana-condops.s
new file mode 100644
index 00000000000..562cf7384f7
--- /dev/null
+++ b/gas/testsuite/gas/riscv/x-ventana-condops.s
@@ -0,0 +1,4 @@
+target:
+	vt.maskc	a0, a1, a2
+	vt.maskcn	a0, a3, a4
+
diff --git a/include/opcode/riscv-opc.h b/include/opcode/riscv-opc.h
index 0b8cc6c7ddb..07c613163b7 100644
--- a/include/opcode/riscv-opc.h
+++ b/include/opcode/riscv-opc.h
@@ -2029,6 +2029,11 @@
 #define MASK_HSV_W 0xfe007fff
 #define MATCH_HSV_D 0x6e004073
 #define MASK_HSV_D 0xfe007fff
+/* Vendor-specific (Ventana Microsystems) XVentanaCondOps instructions */
+#define MATCH_VT_MASKC 0x607b
+#define MASK_VT_MASKC 0xfe00707f
+#define MATCH_VT_MASKCN 0x707b
+#define MASK_VT_MASKCN 0xfe00707f
 /* Privileged CSR addresses.  */
 #define CSR_USTATUS 0x0
 #define CSR_UIE 0x4
@@ -2628,6 +2633,8 @@ DECLARE_INSN(hsv_b, MATCH_HSV_B, MASK_HSV_B)
 DECLARE_INSN(hsv_h, MATCH_HSV_H, MASK_HSV_H)
 DECLARE_INSN(hsv_w, MATCH_HSV_W, MASK_HSV_W)
 DECLARE_INSN(hsv_d, MATCH_HSV_D, MASK_HSV_D)
+DECLARE_INSN(vt_maskc, MATCH_VT_MASKC, MASK_VT_MASKC)
+DECLARE_INSN(vt_maskcn, MATCH_VT_MASKCN, MASK_VT_MASKCN)
 #endif /* DECLARE_INSN */
 #ifdef DECLARE_CSR
 /* Privileged CSRs.  */
diff --git a/include/opcode/riscv.h b/include/opcode/riscv.h
index 048ab0a5d68..9384c6eb84b 100644
--- a/include/opcode/riscv.h
+++ b/include/opcode/riscv.h
@@ -388,6 +388,7 @@ enum riscv_insn_class
   INSN_CLASS_V,
   INSN_CLASS_ZVEF,
   INSN_CLASS_SVINVAL,
+  INSN_CLASS_XVENTANACONDOPS,
 };
 
 /* This structure holds information for a particular instruction.  */
diff --git a/opcodes/riscv-opc.c b/opcodes/riscv-opc.c
index 2da0f7cf0a4..6c70c5b99f3 100644
--- a/opcodes/riscv-opc.c
+++ b/opcodes/riscv-opc.c
@@ -1753,6 +1753,10 @@ const struct riscv_opcode riscv_opcodes[] =
 {"hsv.w",       0, INSN_CLASS_I, "t,0(s)", MATCH_HSV_W, MASK_HSV_W, match_opcode, INSN_DREF|INSN_4_BYTE },
 {"hsv.d",      64, INSN_CLASS_I, "t,0(s)", MATCH_HSV_D, MASK_HSV_D, match_opcode, INSN_DREF|INSN_8_BYTE },
 
+/* Vendor-specific (Ventana Microsystems) XVentanaCondOps instructions */
+{"vt.maskc",    0, INSN_CLASS_XVENTANACONDOPS, "d,s,t", MATCH_VT_MASKC, MASK_VT_MASKC, match_opcode, 0 },
+{"vt.maskcn",   0, INSN_CLASS_XVENTANACONDOPS, "d,s,t", MATCH_VT_MASKCN, MASK_VT_MASKCN, match_opcode, 0 },
+
 /* Terminate the list.  */
 {0, 0, INSN_CLASS_NONE, 0, 0, 0, 0, 0}
 };
-- 
2.33.1

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