[clang] Fix -fno-unsafe-math-optimizations behavior (PR #89473)

[Andy Kaylor via cfe-commits]

================
@@ -318,12 +320,12 @@
 
 // RUN: %clang -### -fassociative-math -freciprocal-math -fno-signed-zeros \
 // RUN:     -fno-trapping-math -ftrapping-math -c %s 2>&1 \
-// RUN:   | FileCheck --check-prefix=CHECK-NO-REASSOC-NO-UNSAFE-MATH %s
+// RUN:   | FileCheck --check-prefix=CHECK-NO-UNSAFE-MATH %s
 
 // CHECK-NO-REASSOC-NO-UNSAFE-MATH: "-cc1"
-// CHECK-NO-REASSOC-NO_UNSAFE-MATH-NOT: "-funsafe-math-optimizations"
-// CHECK-NO-REASSOC-NO_UNSAFE-MATH-NOT: "-mreassociate"
-// CHECK-NO-REASSOC-NO_UNSAFE-MATH-NOT: "-funsafe-math-optimizations"
+// CHECK-NO-REASSOC-NO-UNSAFE-MATH-NOT: "-funsafe-math-optimizations"
+// CHECK-NO-REASSOC-NO-UNSAFE-MATH-NOT: "-mreassociate"
+// CHECK-NO-REASSOC-NO-UNSAFE-MATH-NOT: "-funsafe-math-optimizations"
----------------
andykaylor wrote:

I'm not sure what this case was originally trying to do, but it seems that I can make CHECK, CHECK-NOT, and CHECK-SAME in a limited way. Specifically, CHECK-NOT doesn't reset the line used for CHECK-SAME. So if I have checks like this:
```
CHECK: foo
CHECK-NOT: bar
CHECK-SAME: fubar
CHECK-NOT: bar
```
The string "foo fubar" will pass, the string "foo bar fubar" will fail the first CHECK-NOT test, and "foo fubar bar" will fail the second CHECK-NOT test.

I think I can update this test such that it continues to use "-cc1" as the starting check for the options produced, and uses CHECK-SAME for the FP-related options it expects to be produced, and any options that should not be produced can be verified with a CHECK-NOT before and after the CHECK-SAME.

https://github.com/llvm/llvm-project/pull/89473