[clang] [llvm] [clang] report inlining decisions with -Wattribute-{warning|error} (PR #73552)

[Nick Desaulniers via cfe-commits]

================
@@ -455,18 +455,11 @@ void DiagnosticInfoDontCall::print(DiagnosticPrinter &DP) const {
 SmallVector<std::string> DiagnosticInfoDontCall::getInliningDecisions() const {
   SmallVector<std::string> InliningDecisions;
 
-  if (MDN) {
-    const MDOperand &MO = MDN->getOperand(0);
-    if (auto *MDT = dyn_cast<MDTuple>(MO)) {
-      for (const MDOperand &MO : MDT->operands()) {
-        if (auto *S = dyn_cast<MDString>(MO)) {
+  if (MDN)
+    if (auto *MDT = dyn_cast<MDTuple>(MDN->getOperand(0)))
+      for (const MDOperand &MO : MDT->operands())
+        if (auto *S = dyn_cast<MDString>(MO))
           InliningDecisions.push_back(S->getString().str());
-        }
-      }
-    } else if (auto *S = dyn_cast<MDString>(MO)) {
-      InliningDecisions.push_back(S->getString().str());
-    }
-  }
----------------
nickdesaulniers wrote:

This change is wrong; it seems I don't have this captured in the existing tests, but doing a local integration test:

```c
#include <string.h>
__attribute__((error("bad memcpy"))) void bad(void);

static void *my_memcpy(void *restrict dest, size_t dest_size,
                       const void *restrict src, size_t src_size,
                       size_t n) {
    if (n > dest_size || n > src_size)
        bad();
    return memcpy(dest, src, n);
}

void my_driver (void) {
    unsigned char src [42], dst [42];
    my_memcpy(dst, 42, src, 42, 0);
    my_memcpy(dst, 42, src, 42, 42);
    my_memcpy(dst, 42, src, 42, 4096);
    my_memcpy(dst, 42, src, 42, 1);
}
```
Before this change:
```sh
/tmp/x.c:8:9: error: call to 'bad' declared with 'error' attribute: bad memcpy
    8 |         bad();
      |         ^
/tmp/x.c:8:9: note: called by function 'my_memcpy'
/tmp/x.c:8:9: note: inlined by function 'my_driver'
```
After this change:
```sh
$ /tmp/x.c:8:9: error: call to 'bad' declared with 'error' attribute: bad memcpy
    8 |         bad();
      |         ^
/tmp/x.c:8:9: note: called by function 'my_memcpy'
1 error generated.
```

https://github.com/llvm/llvm-project/pull/73552