[CIR][CIRGen] Implement support for printf builtin

clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

@@ -27,12 +27,20 @@
 #include "mlir/Dialect/Func/IR/FuncOps.h"
 #include "mlir/IR/Value.h"
 #include "clang/CIR/Dialect/IR/CIRDialect.h"
+#include "llvm/Support/ErrorHandling.h"
 
 using namespace cir;
 using namespace clang;
 using namespace mlir::cir;
 using namespace llvm;
 
+static RValue buildLibraryCall(CIRGenFunction &CGF, const FunctionDecl *FD,
+                               const CallExpr *E,
+                               mlir::Operation *calleeValue) {
+  auto callee = CIRGenCallee::forDirect(calleeValue, GlobalDecl(FD));
+  return CGF.buildCall(E->getCallee()->getType(), callee, E, ReturnValueSlot());
+}
+
 RValue CIRGenFunction::buildBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
                                         const CallExpr *E,
                                         ReturnValueSlot ReturnValue) {
@@ -334,6 +342,13 @@ RValue CIRGenFunction::buildBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     llvm_unreachable("NYI");
     break;
 
+  case Builtin::BIprintf:
+    if (getTarget().getTriple().isNVPTX() ||
+        getTarget().getTriple().isAMDGCN()) {
+      llvm_unreachable("NYI");
+    }
+    break;
+
   // C++ std:: builtins.
   case Builtin::BImove:
   case Builtin::BImove_if_noexcept:
@@ -387,7 +402,8 @@ RValue CIRGenFunction::buildBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
   // If this is a predefined lib function (e.g. malloc), emit the call
   // using exactly the normal call path.
   if (getContext().BuiltinInfo.isPredefinedLibFunction(BuiltinID))
-    llvm_unreachable("NYI");
+    return buildLibraryCall(*this, FD, E,
+                            buildScalarExpr(E->getCallee()).getDefiningOp());
 
   // Check that a call to a target specific builtin has the correct target
   // features.

clang/lib/CIR/CodeGen/CIRGenCall.cpp

@@ -19,12 +19,15 @@
 
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/GlobalDecl.h"
+#include "clang/CIR/Dialect/IR/CIRDialect.h"
 #include "clang/CIR/Dialect/IR/CIRTypes.h"
+#include <cassert>
 
 #include "mlir/Dialect/Func/IR/FuncOps.h"
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/BuiltinOps.h"
 #include "mlir/IR/BuiltinTypes.h"
+#include "mlir/IR/SymbolTable.h"
 #include "mlir/IR/Types.h"
 
 using namespace cir;
@@ -503,6 +506,16 @@ RValue CIRGenFunction::buildCall(const CIRGenFunctionInfo &CallInfo,
   } else if (auto loadOp = dyn_cast<mlir::cir::LoadOp>(CalleePtr)) {
     theCall = builder.create<mlir::cir::CallOp>(callLoc, loadOp->getResult(0),
                                                 CIRFuncTy, CIRCallArgs);
+  } else if (auto getGlobalOp = dyn_cast<mlir::cir::GetGlobalOp>(CalleePtr)) {
+    // FIXME(cir): This peephole optimization to avoids indirect calls for
+    // builtins. This should be fixed in the builting declaration instead by not
+    // emitting an unecessary get_global in the first place.
+    auto *globalOp = mlir::SymbolTable::lookupSymbolIn(CGM.getModule(),
+                                                       getGlobalOp.getName());
+    assert(getGlobalOp && "undefined global function");
+    auto callee = llvm::dyn_cast<mlir::cir::FuncOp>(globalOp);
+    assert(callee && "operation is not a function");
+    theCall = builder.create<mlir::cir::CallOp>(callLoc, callee, CIRCallArgs);
   } else {
     llvm_unreachable("expected call variant to be handled");
   }

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

@@ -604,6 +604,13 @@ class CIRGetGlobalOpLowering
   mlir::LogicalResult
   matchAndRewrite(mlir::cir::GetGlobalOp op, OpAdaptor adaptor,
                   mlir::ConversionPatternRewriter &rewriter) const override {
+    // FIXME(cir): Premature DCE to avoid lowering stuff we're not using. CIRGen
+    // should mitigate this and not emit the get_global.
+    if (op->getUses().empty()) {
+      rewriter.eraseOp(op);
+      return mlir::success();
+    }
+
     auto type = getTypeConverter()->convertType(op.getType());
     auto symbol = op.getName();
     rewriter.replaceOpWithNewOp<mlir::LLVM::AddressOfOp>(op, type, symbol);

clang/test/CIR/Executables/hello.c

@@ -2,7 +2,7 @@
 // RUN: %t | FileCheck %s
 // REQUIRES: system-linux
 // REQUIRES: target-linux
-int printf(const char *format);
+int printf(const char *restrict, ...);
 
 int main (void) {
     printf ("Hello, world!\n");