[AMDGPU] Add a pass to promote bitcast calls

AMDGPU currently only supports direct calls, but at lower optimisation levels it
fails to lower statically direct calls which appear indirect due to a bitcast.

Add a pass to visit all CallSites and use CallPromotionUtils to "devirtualize"
calls.

Differential Revision: https://reviews.llvm.org/D52741

llvm-svn: 345382

1 files changed, 63 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUFixFunctionBitcasts.cpp b/llvm/lib/Target/AMDGPU/AMDGPUFixFunctionBitcasts.cpp
new file mode 100644
index 00000000000..6e2a981d339
--- /dev/null
+++ b/llvm/lib/Target/AMDGPU/AMDGPUFixFunctionBitcasts.cpp
@@ -0,0 +1,63 @@
+//===-- AMDGPUFixFunctionBitcasts.cpp - Fix function bitcasts -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Promote indirect (bitcast) calls to direct calls when they are statically
+/// known to be direct. Required when InstCombine is not run (e.g. at OptNone)
+/// because AMDGPU does not support indirect calls.
+///
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/Transforms/Utils/CallPromotionUtils.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "amdgpu-fix-function-bitcasts"
+
+namespace {
+class AMDGPUFixFunctionBitcasts final
+    : public ModulePass,
+      public InstVisitor<AMDGPUFixFunctionBitcasts> {
+
+  bool runOnModule(Module &M) override;
+
+  bool Modified;
+
+public:
+  void visitCallSite(CallSite CS) {
+    if (CS.getCalledFunction())
+      return;
+    auto Callee = dyn_cast<Function>(CS.getCalledValue()->stripPointerCasts());
+    if (Callee && isLegalToPromote(CS, Callee)) {
+      promoteCall(CS, Callee);
+      Modified = true;
+    }
+  }
+
+  static char ID;
+  AMDGPUFixFunctionBitcasts() : ModulePass(ID) {}
+};
+} // End anonymous namespace
+
+char AMDGPUFixFunctionBitcasts::ID = 0;
+char &llvm::AMDGPUFixFunctionBitcastsID = AMDGPUFixFunctionBitcasts::ID;
+INITIALIZE_PASS(AMDGPUFixFunctionBitcasts, DEBUG_TYPE,
+                "Fix function bitcasts for AMDGPU", false, false)
+
+ModulePass *llvm::createAMDGPUFixFunctionBitcastsPass() {
+  return new AMDGPUFixFunctionBitcasts();
+}
+
+bool AMDGPUFixFunctionBitcasts::runOnModule(Module &M) {
+  Modified = false;
+  visit(M);
+  return Modified;
+}