Fix Float16 capability

For 16-bit floating point constants we have to emit the Float16
capability. The implementation is based on checking if cl_khr_fp16
extension from a source langue (OpenCL C) was enabled.
This commit fixes a bug: we should check for *source* extension instead
of SPIR-V extension.

Signed-off-by: Alexey Sotkin <alexey.sotkin@intel.com>

lib/SPIRV/libSPIRV/SPIRVType.h

@@ -191,7 +191,7 @@ class SPIRVTypeFloat : public SPIRVType {
     SPIRVCapVec CV;
     if (isTypeFloat(16)) {
       CV.push_back(CapabilityFloat16Buffer);
-      auto Extensions = getModule()->getExtension();
+      auto Extensions = getModule()->getSourceExtension();
       if (std::any_of(Extensions.begin(), Extensions.end(),
                       [](const std::string &I) { return I == "cl_khr_fp16"; }))
         CV.push_back(CapabilityFloat16);

test/half_extension.ll

@@ -13,7 +13,8 @@
 ; RUN: llvm-spirv %t.bc -o %t.spv
 ; RUN: spirv-val %t.spv
 
-; CHECK-SPIRV: {{[0-9]+}} Capability Float16
+; CHECK-SPIRV-DAG: {{[0-9]+}} Capability Float16Buffer
+; CHECK-SPIRV-DAG: {{[0-9]+}} Capability Float16
 
 ; ModuleID = 'main'
 target datalayout = "e-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-n8:16:32:64"