[SPIRV] Add option to add all KHR extensions (#145535)

In DXC, there is an option to enable all KHR extension. I would like to
extend the existing `-spirv-ext` backend commandline option to have the
same capability. It is like the special case for `all` execept it only
adds the `SPV_KHR_*` extensions.

Part of #137650.

Author: s-perron

llvm/lib/Target/SPIRV/SPIRVCommandLine.cpp

@@ -121,6 +121,13 @@ bool SPIRVExtensionsParser::parse(cl::Option &O, StringRef ArgName,
       continue;
     }
 
+    if (Token.size() == 3 && Token.upper() == "KHR") {
+      for (const auto &[ExtensionName, ExtensionEnum] : SPIRVExtensionMap)
+        if (StringRef(ExtensionName).starts_with("SPV_KHR_"))
+          EnabledExtensions.insert(ExtensionEnum);
+      continue;
+    }
+
     if (Token.empty() || (!Token.starts_with("+") && !Token.starts_with("-")))
       return O.error("Invalid extension list format: " + Token.str());
 

llvm/test/CodeGen/SPIRV/extensions/enable-all-extensions-but-one.ll

@@ -1,4 +1,6 @@
 ; RUN: llc -verify-machineinstrs -O0 -mtriple=spirv32-unknown-unknown --spirv-ext=all,-SPV_INTEL_arbitrary_precision_integers %s -o - | FileCheck %s
+; RUN: llc -verify-machineinstrs -O0 -mtriple=spirv32-unknown-unknown --spirv-ext=KHR %s -o - | FileCheck %s
+; RUN: llc -verify-machineinstrs -O0 -mtriple=spirv32-unknown-unknown --spirv-ext=khr %s -o - | FileCheck %s
 
 define i6 @foo() {
   %call = tail call i32 @llvm.bitreverse.i32(i32 42)