[clang] [Clang][RISCV] Recognize unsupport target feature by supporting isValidFeatureName (PR #106495)

[Michael Maitland via cfe-commits]

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@@ -4,3 +4,12 @@
 int __attribute__((target("arch=rv64g"))) foo(void) { return 0; }
 //expected-error at +1 {{redefinition of 'foo'}}
 int __attribute__((target("arch=rv64gc"))) foo(void) { return 0; }
+
+//expected-warning at +1 {{unsupported 'notafeature' in the 'target' attribute string; 'target' attribute ignored}}
+int __attribute__((target("arch=+notafeature"))) UnsupportFeature(void) { return 0; }
+
+//expected-warning at +1 {{unsupported 'arch=+zba,zbb' in the 'target' attribute string; 'target' attribute ignored}}
+int __attribute__((target("arch=+zba,zbb"))) WithoutAddSigned(void) { return 0; }
+
+//expected-warning at +1 {{unsupported 'arch=zba' in the 'target' attribute string; 'target' attribute ignored}}
+int __attribute__((target("arch=zba"))) WithoutAddSigned2(void) { return 0; }
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michaelmaitland wrote:

should we add a test for `arch=-notafeature`?

https://github.com/llvm/llvm-project/pull/106495