[PATCH v2 3/3] Hexagon (target/hexagon) Only pass env to generated helper when needed

[Taylor Simpson <ltaylorsimpson@gmail.com>]

Currently, we pass env to every generated helper.  When the semantics of
the instruction only depend on the arguments, this is unnecessary and
adds extra overhead to the helper call.

We add the TCG_CALL_NO_RWG_SE flag to any non-HVX helpers that don't get
the ptr to env.

The A2_nop and SA1_setin1 instructions end up with no arguments.  This
results in a "old-style function definition" error from the compiler, so
we write overrides for them.

With this change, the number of helpers with env argument is
    idef-parser enabled:    329 total, 23 with env
    idef-parser disabled:   1543 total, 550 with env

Signed-off-by: Taylor Simpson <ltaylorsimpson@gmail.com>
---
 target/hexagon/gen_tcg.h            |  3 +++
 target/hexagon/gen_helper_protos.py | 10 +++++++++-
 target/hexagon/hex_common.py        | 23 ++++++++++++++++++-----
 3 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/target/hexagon/gen_tcg.h b/target/hexagon/gen_tcg.h
index 1c4391b415..e9ac2e3fe0 100644
--- a/target/hexagon/gen_tcg.h
+++ b/target/hexagon/gen_tcg.h
@@ -1369,3 +1369,6 @@
         gen_helper_raise_exception(tcg_env, excp); \
     } while (0)
 #endif
+
+#define fGEN_TCG_A2_nop(SHORTCODE) do { } while (0)
+#define fGEN_TCG_SA1_setin1(SHORTCODE) tcg_gen_movi_tl(RdV, -1)
diff --git a/target/hexagon/gen_helper_protos.py b/target/hexagon/gen_helper_protos.py
index c82b0f54e4..6e98429752 100755
--- a/target/hexagon/gen_helper_protos.py
+++ b/target/hexagon/gen_helper_protos.py
@@ -40,7 +40,15 @@ def gen_helper_prototype(f, tag, tagregs, tagimms):
         declared.append(arg.proto_arg)
 
     arguments = ", ".join(declared)
-    f.write(f"DEF_HELPER_{len(declared) - 1}({tag}, {arguments})\n")
+
+    ## Add the TCG_CALL_NO_RWG_SE flag to helpers that don't take the env
+    ## argument and aren't HVX instructions.  Since HVX instructions take
+    ## pointers to their arguments, they will have side effects.
+    if hex_common.need_env(tag) or hex_common.is_hvx_insn(tag):
+        f.write(f"DEF_HELPER_{len(declared) - 1}({tag}, {arguments})\n")
+    else:
+        f.write(f"DEF_HELPER_FLAGS_{len(declared) - 1}({tag}, "
+                f"TCG_CALL_NO_RWG_SE, {arguments})\n")
 
 
 def main():
diff --git a/target/hexagon/hex_common.py b/target/hexagon/hex_common.py
index eb28aa98fe..ee08195aba 100755
--- a/target/hexagon/hex_common.py
+++ b/target/hexagon/hex_common.py
@@ -206,6 +206,18 @@ def need_sp(tag):
     return "A_IMPLICIT_READS_SP" in attribdict[tag]
 
 
+def is_hvx_insn(tag):
+    return "A_CVI" in attribdict[tag]
+
+
+def need_env(tag):
+    return ("A_STORE" in attribdict[tag] or
+            "A_LOAD" in attribdict[tag] or
+            "A_CVI_GATHER" in attribdict[tag] or
+            "A_CVI_SCATTER" in attribdict[tag] or
+            "A_IMPLICIT_WRITES_USR" in attribdict[tag])
+
+
 def need_slot(tag):
     if (
         "A_CVI_SCATTER" not in attribdict[tag]
@@ -1069,11 +1081,12 @@ def helper_args(tag, regs, imms):
     args = []
 
     ## First argument is the CPU state
-    args.append(HelperArg(
-        "env",
-        "tcg_env",
-        "CPUHexagonState *env"
-    ))
+    if need_env(tag):
+        args.append(HelperArg(
+            "env",
+            "tcg_env",
+            "CPUHexagonState *env"
+        ))
 
     ## For predicated instructions, we pass in the destination register
     if is_predicated(tag):
-- 
2.34.1