[SPIR-V] Disable opaque pointers in relese 15

[Anastasia]

Summary

As discussed on RFC mapping into SPIR-V requires pointer being preserved in some cases: https://discourse.llvm.org/t/rfc-better-support-for-typed-pointers-in-an-opaque-pointer-world/63339/23?u=anastasiastulova

As the work is still unfinished the best approach is to continue using pointer types.

Note that this change is only planned to be committed in release 15 branch.

This fixing PR56660.

[Anastasia]

CC to @linjamaki in case there is anything else/different needed for HIP.

[nikic]

LG from my side, as a temporary workaround.

[linjamaki]

In D130766#3687240, @Anastasia wrote:

CC to @linjamaki in case there is anything else/different needed for HIP.

LGTM.

[iliya-diyachkov]

Looks good to me.

clang/lib/Driver/ToolChains/Clang.cpp

void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   // Push all default warning arguments that are specific to
   // the given target.  These come before user provided warning options
   // are provided.
   TC.addClangWarningOptions(CmdArgs);
 
   // FIXME: Subclass ToolChain for SPIR and move this to addClangWarningOptions.
-  if (Triple.isSPIR() || Triple.isSPIRV())
+  if (Triple.isSPIR() || Triple.isSPIRV()) {
     CmdArgs.push_back("-Wspir-compat");
+    // SPIR-V support still needs pointer types in some cases as recovering
+    // type from pointer uses is not always possible e.g. for extern functions
+    // (see PR56660).
+    CmdArgs.push_back("-no-opaque-pointers");
+  }
 
   // Select the appropriate action.
   RewriteKind rewriteKind = RK_None;
 
   // If CollectArgsForIntegratedAssembler() isn't called below, claim the args
   // it claims when not running an assembler. Otherwise, clang would emit
   // "argument unused" warnings for assembler flags when e.g. adding "-E" to
   // flags while debugging something. That'd be somewhat inconvenient, and it's

clang/test/Driver/spirv-toolchain.cl

 // Check object emission.
 // RUN: %clang -### --target=spirv64 -x cl -c %s 2>&1 | FileCheck --check-prefix=SPV64 %s
 // RUN: %clang -### --target=spirv64 %s 2>&1 | FileCheck --check-prefix=SPV64 %s
 // RUN: %clang -### --target=spirv64 -x ir -c %s 2>&1 | FileCheck --check-prefix=SPV64 %s
 // RUN: %clang -### --target=spirv64 -x clcpp -c %s 2>&1 | FileCheck --check-prefix=SPV64 %s
 // RUN: %clang -### --target=spirv64 -x c -c %s 2>&1 | FileCheck --check-prefix=SPV64 %s
 
 // SPV64: "-cc1" "-triple" "spirv64"
+// SPV64-SAME: "-no-opaque-pointers"
 // SPV64-SAME: "-o" [[BC:".*bc"]]
 // SPV64: {{llvm-spirv.*"}} [[BC]] "-o" {{".*o"}}
 
 // RUN: %clang -### --target=spirv32 -x cl -c %s 2>&1 | FileCheck --check-prefix=SPV32 %s
 // RUN: %clang -### --target=spirv32 %s 2>&1 | FileCheck --check-prefix=SPV32 %s
 // RUN: %clang -### --target=spirv32 -x ir -c %s 2>&1 | FileCheck --check-prefix=SPV32 %s
 // RUN: %clang -### --target=spirv32 -x clcpp -c %s 2>&1 | FileCheck --check-prefix=SPV32 %s
 // RUN: %clang -### --target=spirv32 -x c -c %s 2>&1 | FileCheck --check-prefix=SPV32 %s
 
 // SPV32: "-cc1" "-triple" "spirv32"
+// SPV32-SAME: "-no-opaque-pointers"
 // SPV32-SAME: "-o" [[BC:".*bc"]]
 // SPV32: {{llvm-spirv.*"}} [[BC]] "-o" {{".*o"}}
 
 //-----------------------------------------------------------------------------
 // Check Assembly emission.
 // RUN: %clang -### --target=spirv64 -x cl -S %s 2>&1 | FileCheck --check-prefix=SPT64 %s
 // RUN: %clang -### --target=spirv64 -x ir -S %s 2>&1 | FileCheck --check-prefix=SPT64 %s
 // RUN: %clang -### --target=spirv64 -x clcpp -c %s 2>&1 | FileCheck --check-prefix=SPV64 %s