[clang] [HLSL] Add `-Gis` option to clang-dxc (PR #146448)

[Chris B via cfe-commits]

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+// RUN: %clang_dxc -T lib_6_4 -Gis %s 2>&1 -### | FileCheck -check-prefix=Gis %s
+// RUN: %clang_dxc -T lib_6_4 %s 2>&1 -### | FileCheck -check-prefix=NO_Gis %s
+// RUN: not %clang_dxc -T lib_6_4 /Gis gibberish -### %s 2>&1 | FileCheck -check-prefix=CHECK-ERR %s
+
+// Gis: "-fmath-errno" "-ffp-contract=off" "-frounding-math" "-ffp-exception-behavior=strict" "-complex-range=full"
+// assert expected floating point options are present
+// NO_Gis-NOT: "-fmath-errno" "-ffp-contract=off" "-frounding-math" "-ffp-exception-behavior=strict" "-complex-range=full"
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llvm-beanz wrote:

It would probably be better to split this into one `NO_Gis-NOT` line per flag, that way the order of the flags doesn't matter it will verify that none of the flags ever appear.

https://github.com/llvm/llvm-project/pull/146448