[OpenCL] Makes kernels use the SPIR_KERNEL CC by default.

Rationale: OpenCL kernels are called via an explicit runtime API
with arguments set with clSetKernelArg(), not as normal sub-functions.
Return SPIR_KERNEL by default as the kernel calling convention to ensure
the fingerprint is fixed such way that each OpenCL argument gets one
matching argument in the produced kernel function argument list to enable
feasible implementation of clSetKernelArg() with aggregates etc. In case
we would use the default C calling conv here, clSetKernelArg() might
break depending on the target-specific conventions; different targets
might split structs passed as values to multiple function arguments etc.

https://reviews.llvm.org/D33639

llvm-svn: 304389

3 files changed, 35 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/ABIInfo.h b/clang/lib/CodeGen/ABIInfo.h
index c0be60ef53b..e4dce2f2a00 100644
--- a/clang/lib/CodeGen/ABIInfo.h
+++ b/clang/lib/CodeGen/ABIInfo.h
@@ -149,7 +149,6 @@ namespace swiftcall {
       return info->supportsSwift();
     }
   };
-
 }  // end namespace CodeGen
 }  // end namespace clang
 
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index c677d9887ac..8f405eee6e5 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -707,6 +707,12 @@ CodeGenTypes::arrangeCall(const CGFunctionInfo &signature,
                                  signature.getRequiredArgs());
 }
 
+namespace clang {
+namespace CodeGen {
+void computeSPIRKernelABIInfo(CodeGenModule &CGM, CGFunctionInfo &FI);
+}
+}
+
 /// Arrange the argument and result information for an abstract value
 /// of a given function type.  This is the method which all of the
 /// above functions ultimately defer to.
@@ -741,12 +747,16 @@ CodeGenTypes::arrangeLLVMFunctionInfo(CanQualType resultType,
   bool inserted = FunctionsBeingProcessed.insert(FI).second;
   (void)inserted;
   assert(inserted && "Recursively being processed?");
-  
+
   // Compute ABI information.
-  if (info.getCC() != CC_Swift) {
-    getABIInfo().computeInfo(*FI);
-  } else {
+  if (CC == llvm::CallingConv::SPIR_KERNEL) {
+    // Force target independent argument handling for the host visible
+    // kernel functions.
+    computeSPIRKernelABIInfo(CGM, *FI);
+  } else if (info.getCC() == CC_Swift) {
     swiftcall::computeABIInfo(CGM, *FI);
+  } else {
+    getABIInfo().computeInfo(*FI);
   }
 
   // Loop over all of the computed argument and return value info.  If any of
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index d0ba74119b7..427ec06a2ff 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -398,7 +398,17 @@ TargetCodeGenInfo::getDependentLibraryOption(llvm::StringRef Lib,
 }
 
 unsigned TargetCodeGenInfo::getOpenCLKernelCallingConv() const {
-  return llvm::CallingConv::C;
+  // OpenCL kernels are called via an explicit runtime API with arguments
+  // set with clSetKernelArg(), not as normal sub-functions.
+  // Return SPIR_KERNEL by default as the kernel calling convention to
+  // ensure the fingerprint is fixed such way that each OpenCL argument
+  // gets one matching argument in the produced kernel function argument
+  // list to enable feasible implementation of clSetKernelArg() with
+  // aggregates etc. In case we would use the default C calling conv here,
+  // clSetKernelArg() might break depending on the target-specific
+  // conventions; different targets might split structs passed as values
+  // to multiple function arguments etc.
+  return llvm::CallingConv::SPIR_KERNEL;
 }
 
 llvm::Constant *TargetCodeGenInfo::getNullPointer(const CodeGen::CodeGenModule &CGM,
@@ -8068,8 +8078,18 @@ public:
                     CodeGen::CodeGenModule &M) const override;
   unsigned getOpenCLKernelCallingConv() const override;
 };
+
 } // End anonymous namespace.
 
+namespace clang {
+namespace CodeGen {
+void computeSPIRKernelABIInfo(CodeGenModule &CGM, CGFunctionInfo &FI) {
+  DefaultABIInfo SPIRABI(CGM.getTypes());
+  SPIRABI.computeInfo(FI);
+}
+}
+}
+
 /// Emit SPIR specific metadata: OpenCL and SPIR version.
 void SPIRTargetCodeGenInfo::emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
                                          CodeGen::CodeGenModule &CGM) const {