Hi Richard,

> > +  /* The smallest set of feature bits to toggle to enable this
> > + option.  */
> >    aarch64_feature_flags flag_canonical;
> > -  aarch64_feature_flags flags_on;
> > -  aarch64_feature_flags flags_off;
> > +  /* If this feature is turned on, these bits also need to be turned
> > + on.  */  const unsigned long flags_on;
> > +  /* If this feature is turned off, these bits also need to be turned
> > + off.  */  const unsigned long flags_off;
> 
> Please don't undo the aarch64_feature_flags abstraction.  "long" isn't
> enough for x86_32 to aarch64 cross-compilers (yes, I know, but still), and
> we're not far off running out of room in the uint64_t.  The point of the
> abstraction was to reduce the number of changes that we need once we
> have 65 or more features, architecture levels, etc.
> 

Sorry, the duplicate copy confused me.


Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.

Ok for master? I think it needs backporting but need to verify older compilers.
If one is required, OK for backporting?

Thanks,
Tamar

gcc/ChangeLog:

	* common/config/aarch64/aarch64-common.cc
	(struct aarch64_option_extension): Add native_detect_p and document struct
	a bit more.
	(all_extensions): Set new field native_detect_p.
	* config/aarch64/aarch64.cc (struct aarch64_option_extension): Delete
	unused struct.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/cpunative/info_19: New test.
	* gcc.target/aarch64/cpunative/info_20: New test.
	* gcc.target/aarch64/cpunative/info_21: New test.
	* gcc.target/aarch64/cpunative/info_22: New test.
	* gcc.target/aarch64/cpunative/native_cpu_19.c: New test.
	* gcc.target/aarch64/cpunative/native_cpu_20.c: New test.
	* gcc.target/aarch64/cpunative/native_cpu_21.c: New test.
	* gcc.target/aarch64/cpunative/native_cpu_22.c: New test.

--- inline copy of patch ---

diff --git a/gcc/common/config/aarch64/aarch64-common.cc b/gcc/common/config/aarch64/aarch64-common.cc
index a9695d60197e6585957b293d2d755a557e124d4f..5a5ebfa1b724b173dd01ec71ffd63662037b3b74 100644
--- a/gcc/common/config/aarch64/aarch64-common.cc
+++ b/gcc/common/config/aarch64/aarch64-common.cc
@@ -139,20 +139,28 @@ aarch64_handle_option (struct gcc_options *opts,
 /* An ISA extension in the co-processor and main instruction set space.  */
 struct aarch64_option_extension
 {
+  /* The extension name to pass on to the assembler.  */
   const char *name;
+  /* The smallest set of feature bits to toggle to enable this option.  */
   aarch64_feature_flags flag_canonical;
+  /* If this feature is turned on, these bits also need to be turned on.  */
   aarch64_feature_flags flags_on;
+  /* If this feature is turned off, these bits also need to be turned off.  */
   aarch64_feature_flags flags_off;
+  /* Indicates whether this feature is taken into account during native cpu
+     detection.  */
+  bool native_detect_p;
 };
 
 /* ISA extensions in AArch64.  */
 static constexpr aarch64_option_extension all_extensions[] =
 {
-#define AARCH64_OPT_EXTENSION(NAME, IDENT, C, D, E, F) \
+#define AARCH64_OPT_EXTENSION(NAME, IDENT, C, D, E, FEATURE_STRING) \
   {NAME, AARCH64_FL_##IDENT, feature_deps::IDENT ().explicit_on, \
-   feature_deps::get_flags_off (feature_deps::root_off_##IDENT)},
+   feature_deps::get_flags_off (feature_deps::root_off_##IDENT), \
+   FEATURE_STRING[0]},
 #include "config/aarch64/aarch64-option-extensions.def"
-  {NULL, 0, 0, 0}
+  {NULL, 0, 0, 0, false}
 };
 
 struct processor_name_to_arch
@@ -325,9 +333,13 @@ aarch64_get_extension_string_for_isa_flags
 	outstr += opt.name;
       }
 
-  /* Remove the features in current_flags & ~isa_flags.  */
+  /* Remove the features in current_flags & ~isa_flags.  If the feature does
+     not have an HWCAPs then it shouldn't be taken into account for feature
+     detection because one way or another we can't tell if it's available
+     or not.  */
   for (auto &opt : all_extensions)
-    if (opt.flag_canonical & current_flags & ~isa_flags)
+    if (opt.native_detect_p
+	&& (opt.flag_canonical & current_flags & ~isa_flags))
       {
 	current_flags &= ~opt.flags_off;
 	outstr += "+no";
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index d36b57341b336a81dc2e1a975986b3e37402602a..860aeb3e5fbf655e87284be28cc72648c1cd71f9 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -2808,14 +2808,6 @@ static const struct attribute_spec aarch64_attribute_table[] =
   { NULL,                 0, 0, false, false, false, false, NULL, NULL }
 };
 
-/* An ISA extension in the co-processor and main instruction set space.  */
-struct aarch64_option_extension
-{
-  const char *const name;
-  const unsigned long flags_on;
-  const unsigned long flags_off;
-};
-
 typedef enum aarch64_cond_code
 {
   AARCH64_EQ = 0, AARCH64_NE, AARCH64_CS, AARCH64_CC, AARCH64_MI, AARCH64_PL,
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/info_19 b/gcc/testsuite/gcc.target/aarch64/cpunative/info_19
new file mode 100644
index 0000000000000000000000000000000000000000..616d3b26d03398a8ef3f4cdf4c56b144ecf0b1c2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/info_19
@@ -0,0 +1,9 @@
+processor	: 0
+BogoMIPS	: 100.00
+Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 sm3 sm4 asimddp sha512 sve asimdfhm dit uscat ilrcpc flagm ssbs sb dcpodp sve2 sveaes svepmull svebitperm svesha3 svesm4 flagm2 frint svei8mm svebf16 i8mm bf16 dgh bti
+CPU implementer	: 0x41
+CPU architecture: 8
+CPU variant	: 0x0
+CPU part	: 0xd49
+CPU revision	: 2
+
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/info_20 b/gcc/testsuite/gcc.target/aarch64/cpunative/info_20
new file mode 100644
index 0000000000000000000000000000000000000000..45d45d15f16b927ebdffa80bca76270a7e2ed135
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/info_20
@@ -0,0 +1,9 @@
+processor	: 0
+BogoMIPS	: 100.00
+Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 sm3 sm4 asimddp sha512 sve asimdfhm dit uscat ilrcpc flagm ssbs sb dcpodp sve2 sveaes svepmull svebitperm svesha3 svesm4 flagm2 frint svei8mm svebf16 i8mm bf16 dgh bti paca pacg
+CPU implementer	: 0x41
+CPU architecture: 8
+CPU variant	: 0x0
+CPU part	: 0xd49
+CPU revision	: 2
+
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/info_21 b/gcc/testsuite/gcc.target/aarch64/cpunative/info_21
new file mode 100644
index 0000000000000000000000000000000000000000..3c418a4bee4e2bf009e658def70bd184c4084d16
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/info_21
@@ -0,0 +1,9 @@
+processor	: 0
+BogoMIPS	: 100.00
+Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 sm3 sm4 asimddp sha512 sve asimdfhm dit uscat ilrcpc flagm ssbs sb dcpodp sve2 sveaes svepmull svebitperm svesha3 svesm4 flagm2 frint svei8mm svebf16 i8mm bf16 dgh bti
+CPU implementer	: 0x41
+CPU architecture: 8
+CPU variant	: 0x0
+CPU part	: 0xd08
+CPU revision	: 2
+
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/info_22 b/gcc/testsuite/gcc.target/aarch64/cpunative/info_22
new file mode 100644
index 0000000000000000000000000000000000000000..3147eec1f443b3a7da77a89148c23511846ecd85
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/info_22
@@ -0,0 +1,9 @@
+processor	: 0
+BogoMIPS	: 100.00
+Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 sm3 sm4 asimddp sha512 sve asimdfhm dit uscat ilrcpc flagm ssbs sb dcpodp sve2 sveaes svepmull svebitperm svesha3 svesm4 flagm2 frint svei8mm svebf16 i8mm bf16 dgh bti paca pacg
+CPU implementer	: 0x41
+CPU architecture: 8
+CPU variant	: 0x0
+CPU part	: 0xd08
+CPU revision	: 2
+
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_19.c b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_19.c
new file mode 100644
index 0000000000000000000000000000000000000000..980d3f79dfb03b0d8eb68f691bf2dedf80aed87d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_19.c
@@ -0,0 +1,14 @@
+/* { dg-do compile { target { { aarch64*-*-linux*} && native } } } */
+/* { dg-set-compiler-env-var GCC_CPUINFO "$srcdir/gcc.target/aarch64/cpunative/info_19" } */
+/* { dg-additional-options "-mcpu=native" } */
+
+int main()
+{
+  return 0;
+}
+
+/* { dg-final { scan-assembler {\.arch armv9-a\+crc\+profile\+memtag\+sve2-sm4\+sve2-aes\+sve2-sha3\+sve2-bitperm\+i8mm\+bf16\+nopauth\n} } } */
+
+/* Test one that if the kernel doesn't report the availability of a mandatory
+   feature that it has turned it off for whatever reason.  As such compilers
+   should follow along. */
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_20.c b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_20.c
new file mode 100644
index 0000000000000000000000000000000000000000..117df2b0b6cd5751d9f5175b4343aad9825a6c43
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_20.c
@@ -0,0 +1,15 @@
+/* { dg-do compile { target { { aarch64*-*-linux*} && native } } } */
+/* { dg-set-compiler-env-var GCC_CPUINFO "$srcdir/gcc.target/aarch64/cpunative/info_20" } */
+/* { dg-additional-options "-mcpu=native" } */
+
+int main()
+{
+  return 0;
+}
+
+/* { dg-final { scan-assembler {\.arch armv9-a\+crc\+profile\+memtag\+sve2-sm4\+sve2-aes\+sve2-sha3\+sve2-bitperm\+i8mm\+bf16\n} } } */
+
+/* Check whether features that don't have a midr name during detection are
+   correctly ignored.  These features shouldn't affect the native detection.
+   This particular test checks that predres is not turned off during
+   detection.   */
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_21.c b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_21.c
new file mode 100644
index 0000000000000000000000000000000000000000..efbd02cbdc0638db85e776f1e79043709c11df21
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_21.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target { { aarch64*-*-linux*} && native } } } */
+/* { dg-set-compiler-env-var GCC_CPUINFO "$srcdir/gcc.target/aarch64/cpunative/info_21" } */
+/* { dg-additional-options "-mcpu=native" } */
+
+int main()
+{
+  return 0;
+}
+
+/* { dg-final { scan-assembler {\.arch armv8-a\+crc\+lse\+rcpc\+rdma\+dotprod\+fp16fml\+sb\+ssbs\+sve2-sm4\+sve2-aes\+sve2-sha3\+sve2-bitperm\+i8mm\+bf16\+flagm\n} } } */
+
+/* Check that an Armv8-A core doesn't fall apart on extensions without midr
+   values.  */
diff --git a/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_22.c b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_22.c
new file mode 100644
index 0000000000000000000000000000000000000000..d431d4938265d024891b464ac3d069607b21d8e7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/cpunative/native_cpu_22.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target { { aarch64*-*-linux*} && native } } } */
+/* { dg-set-compiler-env-var GCC_CPUINFO "$srcdir/gcc.target/aarch64/cpunative/info_22" } */
+/* { dg-additional-options "-mcpu=native" } */
+
+int main()
+{
+  return 0;
+}
+
+/* { dg-final { scan-assembler {\.arch armv8-a\+crc\+lse\+rcpc\+rdma\+dotprod\+fp16fml\+sb\+ssbs\+sve2-sm4\+sve2-aes\+sve2-sha3\+sve2-bitperm\+i8mm\+bf16\+flagm\+pauth\n} } } */
+
+/* Check that an Armv8-A core doesn't fall apart on extensions without midr
+   values and that it enables optional features.  */