[PATCH]AArch64: don't override march to assembler with mcpu if march is specified [PR110901]

[Tamar Christina]

Hi All,

When both -mcpu and -march are specified, the value of -march wins out.

This is done correctly for the calls to cc1 and for the assembler directives we
put out in assembly files.

However in the call to as we don't do this and instead use the arch from the
cpu.  This leads to a situation that GCC cannot reliably be used to compile
assembly files which don't have a .arch directive.

This is quite common with .S files which use macros to selectively enable
codepath based on what the preprocessor sees.

The fix is to change MCPU_TO_MARCH_SPEC to not override the march if an march
is already specified.

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

Ok for master?

Thanks,
Tamar

gcc/ChangeLog:

        PR target/110901
        * config/aarch64/aarch64.h (MCPU_TO_MARCH_SPEC): Don't override if
        march is set.

gcc/testsuite/ChangeLog:

        PR target/110901
        * gcc.target/aarch64/options_set_29.c: New test.

---
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 
1ab49e229b080d29187690abdb0c0767c12a157a..218868a5246a19c293c03e7be48107c1b0770e27
 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -1510,7 +1510,7 @@ extern const char *host_detect_local_cpu (int argc, const 
char **argv);
   CONFIG_TUNE_SPEC
 
 #define MCPU_TO_MARCH_SPEC \
-   " %{mcpu=*:-march=%:rewrite_mcpu(%{mcpu=*:%*})}"
+   "%{!march=*:%{mcpu=*:-march=%:rewrite_mcpu(%{mcpu=*:%*})}}"
 
 extern const char *aarch64_rewrite_mcpu (int argc, const char **argv);
 extern const char *is_host_cpu_not_armv8_base (int argc, const char **argv);
diff --git a/gcc/testsuite/gcc.target/aarch64/options_set_29.c 
b/gcc/testsuite/gcc.target/aarch64/options_set_29.c
new file mode 100644
index 
0000000000000000000000000000000000000000..0a68550951ce61422c4cfea50762b2420a92091e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/options_set_29.c
@@ -0,0 +1,11 @@
+/* { dg-do assemble } */
+/* { dg-additional-options "-march=armv8.2-a+sve -mcpu=cortex-a72 -O1 -w -###" 
} */
+
+int main ()
+{
+  return 0;
+}
+
+/* { dg-message "-march=armv8-a\+crc" "no arch from cpu" { xfail *-*-* } 0 } */
+/* { dg-message "-march=armv8\\.2-a\\+sve" "using only sve" { target *-*-* } 0 
} */
+/* { dg-excess-errors "" } */




-- 

diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index 1ab49e229b080d29187690abdb0c0767c12a157a..218868a5246a19c293c03e7be48107c1b0770e27 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -1510,7 +1510,7 @@ extern const char *host_detect_local_cpu (int argc, const char **argv);
   CONFIG_TUNE_SPEC
 
 #define MCPU_TO_MARCH_SPEC \
-   " %{mcpu=*:-march=%:rewrite_mcpu(%{mcpu=*:%*})}"
+   "%{!march=*:%{mcpu=*:-march=%:rewrite_mcpu(%{mcpu=*:%*})}}"
 
 extern const char *aarch64_rewrite_mcpu (int argc, const char **argv);
 extern const char *is_host_cpu_not_armv8_base (int argc, const char **argv);
diff --git a/gcc/testsuite/gcc.target/aarch64/options_set_29.c b/gcc/testsuite/gcc.target/aarch64/options_set_29.c
new file mode 100644
index 0000000000000000000000000000000000000000..0a68550951ce61422c4cfea50762b2420a92091e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/options_set_29.c
@@ -0,0 +1,11 @@
+/* { dg-do assemble } */
+/* { dg-additional-options "-march=armv8.2-a+sve -mcpu=cortex-a72 -O1 -w -###" } */
+
+int main ()
+{
+  return 0;
+}
+
+/* { dg-message "-march=armv8-a\+crc" "no arch from cpu" { xfail *-*-* } 0 } */
+/* { dg-message "-march=armv8\\.2-a\\+sve" "using only sve" { target *-*-* } 0 } */
+/* { dg-excess-errors "" } */