Switch to using -disable-llvm-optzns. Clarify the temporary nature.

Author: AlexVlx

clang/lib/Driver/ToolChains/AMDGPU.cpp

@@ -861,9 +861,16 @@ void AMDGPUToolChain::addClangTargetOptions(
   // For SPIR-V we want to retain the pristine output of Clang CodeGen, since
   // optimizations might lose structure / information that is necessary for
   // generating optimal concrete AMDGPU code.
+  // TODO: using the below option is a temporary placeholder until Clang
+  //       provides the required functionality, which essentially boils down to
+  //       -O0 being refactored / reworked to not imply optnone / remove TBAA.
+  //       Once that is added, we should pivot to that functionality, being
+  //       mindful to not corrupt the user provided and subsequently embedded
+  //       command-line (i.e. if the user asks for -O3 this is what the
+  //       finalisation should use).
   if (getTriple().isSPIRV() &&
-      !DriverArgs.hasArg(options::OPT_disable_llvm_passes))
-    CC1Args.push_back("-disable-llvm-passes");
+      !DriverArgs.hasArg(options::OPT_disable_llvm_optzns))
+    CC1Args.push_back("-disable-llvm-optzns");
 
   if (DeviceOffloadingKind == Action::OFK_None)
     addOpenCLBuiltinsLib(getDriver(), DriverArgs, CC1Args);

clang/test/Driver/spirv-amd-toolchain.c

@@ -14,6 +14,6 @@
 
 // RUN: %clang -### --target=spirv64-amd-amdhsa %s -nogpulib -nogpuinc 2>&1 \
 // RUN:   | FileCheck %s --check-prefix=INVOCATION
-// INVOCATION: "-cc1" "-triple" "spirv64-amd-amdhsa" {{.*}}"-disable-llvm-passes" {{.*}} "-o" "[[OUTPUT:.+]]" "-x" "c"
+// INVOCATION: "-cc1" "-triple" "spirv64-amd-amdhsa" {{.*}}"-disable-llvm-optzns" {{.*}} "-o" "[[OUTPUT:.+]]" "-x" "c"
 // INVOCATION: "{{.*}}llvm-link" "-o" "a.out" "[[OUTPUT]]"
 // INVOCATION: "{{.*}}llvm-spirv" "--spirv-max-version=1.6" "--spirv-ext=+all" "--spirv-allow-unknown-intrinsics" "--spirv-lower-const-expr" "--spirv-preserve-auxdata" "--spirv-debug-info-version=nonsemantic-shader-200" "a.out" "-o" "a.out"