When a non-duplex encoding (parse_bits != 0) fails both decode_normal()
and decode_hvx(), the decoder hit an unreachable.  Instead, handle
the decode failure and raise an exception.

Signed-off-by: Brian Cain <brian.cain@oss.qualcomm.com>
---
 target/hexagon/decode.c              |  3 ++-
 tests/tcg/hexagon/invalid-encoding.c | 20 ++++++++++++++++++++
 tests/tcg/hexagon/Makefile.target    |  6 ++++++
 3 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 tests/tcg/hexagon/invalid-encoding.c

diff --git a/target/hexagon/decode.c b/target/hexagon/decode.c
index 90499fc320..ebb4e02a17 100644
--- a/target/hexagon/decode.c
+++ b/target/hexagon/decode.c
@@ -489,7 +489,8 @@ decode_insns(DisasContext *ctx, Insn *insn, uint32_t encoding)
             insn->iclass = iclass_bits(encoding);
             return 1;
         }
-        g_assert_not_reached();
+        /* Invalid non-duplex encoding */
+        return 0;
     } else {
         uint32_t iclass = get_duplex_iclass(encoding);
         unsigned int slot0_subinsn = get_slot0_subinsn(encoding);
diff --git a/tests/tcg/hexagon/invalid-encoding.c b/tests/tcg/hexagon/invalid-encoding.c
new file mode 100644
index 0000000000..efe914b4e4
--- /dev/null
+++ b/tests/tcg/hexagon/invalid-encoding.c
@@ -0,0 +1,20 @@
+/*
+ * Test that invalid non-duplex encodings are properly rejected.
+ *
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+/*
+ * The encoding 0xffffc000 has parse bits [15:14] = 0b11, making it a
+ * non-duplex instruction and packet end.  The remaining bits do not match
+ * any valid normal or HVX instruction encoding, so this should raise SIGILL.
+ */
+
+int main()
+{
+    asm volatile(
+        ".word 0xffffc000\n"
+        : : : "memory");
+    return 0;
+}
diff --git a/tests/tcg/hexagon/Makefile.target b/tests/tcg/hexagon/Makefile.target
index 7199e29a30..79ebfd56ce 100644
--- a/tests/tcg/hexagon/Makefile.target
+++ b/tests/tcg/hexagon/Makefile.target
@@ -53,6 +53,7 @@ HEX_TESTS += hvx_histogram
 HEX_TESTS += invalid-slots
 HEX_TESTS += invalid-duplex
 HEX_TESTS += invalid-dups
+HEX_TESTS += invalid-encoding
 HEX_TESTS += unaligned_pc
 
 run-and-check-exception = $(call run-test,$2,$3 2>$2.stderr; \
@@ -74,6 +75,11 @@ run-invalid-dups: invalid-dups
 		$(QEMU) $(QEMU_OPTS) $< ; test $$? -eq 132, \
 		TEST, invalid-dups on $(TARGET_NAME))
 
+run-invalid-encoding: invalid-encoding
+	$(call quiet-command, \
+		$(QEMU) $(QEMU_OPTS) $< ; test $$? -eq 132, \
+		TEST, invalid-encoding on $(TARGET_NAME))
+
 HEX_TESTS += test_abs
 HEX_TESTS += test_bitcnt
 HEX_TESTS += test_bitsplit
-- 
2.34.1

On 2/6/26 10:38 AM, Brian Cain wrote:
> When a non-duplex encoding (parse_bits != 0) fails both decode_normal()
> and decode_hvx(), the decoder hit an unreachable.  Instead, handle
> the decode failure and raise an exception.
> 
> Signed-off-by: Brian Cain <brian.cain@oss.qualcomm.com>
> ---
>   target/hexagon/decode.c              |  3 ++-
>   tests/tcg/hexagon/invalid-encoding.c | 20 ++++++++++++++++++++
>   tests/tcg/hexagon/Makefile.target    |  6 ++++++
>   3 files changed, 28 insertions(+), 1 deletion(-)
>   create mode 100644 tests/tcg/hexagon/invalid-encoding.c
> 

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>