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[CIR][CUDA] Support device-side printf (#1475)
The choice of adding a separate file imitates that of OG.
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4 files changed

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4 files changed

+148
-3
lines changed

‎clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp‎

Lines changed: 5 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2340,12 +2340,14 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
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llvm_unreachable("BI__builtin_load_halff NYI");
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case Builtin::BI__builtin_printf:
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llvm_unreachable("BI__builtin_printf NYI");
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case Builtin::BIprintf:
2345-
if (getTarget().getTriple().isNVPTX() ||
2346-
getTarget().getTriple().isAMDGCN()) {
2344+
assert(E->getNumArgs() >= 1);
2345+
if (getTarget().getTriple().isAMDGCN()) {
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llvm_unreachable("BIprintf NYI");
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}
2348+
if (getTarget().getTriple().isNVPTX()) {
2349+
return RValue::get(emitNVPTXDevicePrintfCallExpr(E));
2350+
}
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break;
23502352

23512353
case Builtin::BI__builtin_canonicalize:

‎clang/lib/CIR/CodeGen/CIRGenBuiltinNVPTX.cpp‎

Lines changed: 93 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -80,3 +80,96 @@ mlir::Value CIRGenFunction::emitNVPTXBuiltinExpr(unsigned builtinId,
8080
llvm_unreachable("NYI");
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}
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}
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// vprintf takes two args: A format string, and a pointer to a buffer containing
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// the varargs.
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//
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// For example, the call
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//
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// printf("format string", arg1, arg2, arg3);
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//
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// is converted into something resembling
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//
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// struct Tmp {
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// Arg1 a1;
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// Arg2 a2;
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// Arg3 a3;
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// };
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// char* buf = alloca(sizeof(Tmp));
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// *(Tmp*)buf = {a1, a2, a3};
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// vprintf("format string", buf);
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//
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// `buf` is aligned to the max of {alignof(Arg1), ...}. Furthermore, each of
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// the args is itself aligned to its preferred alignment.
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//
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// Note that by the time this function runs, the arguments have already
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// undergone the standard C vararg promotion (short -> int, float -> double
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// etc). In this function we pack the arguments into the buffer described above.
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mlir::Value packArgsIntoNVPTXFormatBuffer(CIRGenFunction &cgf,
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const CallArgList &args,
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mlir::Location loc) {
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const CIRDataLayout &dataLayout = cgf.CGM.getDataLayout();
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CIRGenBuilderTy &builder = cgf.getBuilder();
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if (args.size() <= 1)
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// If there are no arguments other than the format string,
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// pass a nullptr to vprintf.
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return builder.getNullPtr(cgf.VoidPtrTy, loc);
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llvm::SmallVector<mlir::Type, 8> argTypes;
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for (auto arg : llvm::drop_begin(args))
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argTypes.push_back(arg.getRValue(cgf, loc).getScalarVal().getType());
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// We can directly store the arguments into a struct, and the alignment
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// would automatically be correct. That's because vprintf does not
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// accept aggregates.
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mlir::Type allocaTy =
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cir::StructType::get(&cgf.getMLIRContext(), argTypes, /*packed=*/false,
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/*padded=*/false, StructType::Struct);
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mlir::Value alloca =
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cgf.CreateTempAlloca(allocaTy, loc, "printf_args", nullptr);
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for (auto [i, arg] : llvm::enumerate(llvm::drop_begin(args))) {
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mlir::Value member =
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builder.createGetMember(loc, cir::PointerType::get(argTypes[i]), alloca,
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/*name=*/"", /*index=*/i);
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auto preferredAlign = clang::CharUnits::fromQuantity(
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dataLayout.getPrefTypeAlign(argTypes[i]).value());
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builder.createAlignedStore(loc, arg.getRValue(cgf, loc).getScalarVal(),
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member, preferredAlign);
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}
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return builder.createBitcast(alloca, cgf.VoidPtrTy);
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}
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mlir::Value
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CIRGenFunction::emitNVPTXDevicePrintfCallExpr(const CallExpr *expr) {
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assert(CGM.getTriple().isNVPTX());
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CallArgList args;
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emitCallArgs(args,
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expr->getDirectCallee()->getType()->getAs<FunctionProtoType>(),
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expr->arguments(), expr->getDirectCallee());
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mlir::Location loc = getLoc(expr->getBeginLoc());
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// Except the format string, no non-scalar arguments are allowed for
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// device-side printf.
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bool hasNonScalar =
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llvm::any_of(llvm::drop_begin(args), [&](const CallArg &A) {
159+
return !A.getRValue(*this, loc).isScalar();
160+
});
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if (hasNonScalar) {
162+
CGM.ErrorUnsupported(expr, "non-scalar args to printf");
163+
return builder.getConstInt(loc, SInt32Ty, 0);
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}
165+
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mlir::Value packedData = packArgsIntoNVPTXFormatBuffer(*this, args, loc);
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// int vprintf(char *format, void *packedData);
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auto vprintf = CGM.createRuntimeFunction(
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FuncType::get({cir::PointerType::get(SInt8Ty), VoidPtrTy}, SInt32Ty),
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"vprintf");
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auto formatString = args[0].getRValue(*this, loc).getScalarVal();
173+
return builder.createCallOp(loc, vprintf, {formatString, packedData})
174+
.getResult();
175+
}

‎clang/lib/CIR/CodeGen/CIRGenFunction.h‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1478,6 +1478,8 @@ class CIRGenFunction : public CIRGenTypeCache {
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mlir::Value emitX86BuiltinExpr(unsigned BuiltinID, const CallExpr *E);
14791479
mlir::Value emitNVPTXBuiltinExpr(unsigned builtinID, const CallExpr *expr);
14801480

1481+
mlir::Value emitNVPTXDevicePrintfCallExpr(const CallExpr *expr);
1482+
14811483
/// Given an expression with a pointer type, emit the value and compute our
14821484
/// best estimate of the alignment of the pointee.
14831485
///

‎clang/test/CIR/CodeGen/CUDA/printf.cu‎

Lines changed: 48 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,48 @@
1+
#include "../Inputs/cuda.h"
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// RUN: %clang_cc1 -triple nvptx64-nvidia-cuda -fclangir \
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// RUN: -fcuda-is-device -emit-cir -target-sdk-version=12.3 \
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// RUN: %s -o %t.cir
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// RUN: FileCheck --check-prefix=CIR-DEVICE --input-file=%t.cir %s
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// RUN: %clang_cc1 -triple nvptx64-nvidia-cuda -fclangir \
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// RUN: -fcuda-is-device -emit-llvm -target-sdk-version=12.3 \
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// RUN: %s -o %t.ll
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// RUN: FileCheck --check-prefix=LLVM-DEVICE --input-file=%t.ll %s
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__device__ void printer() {
14+
printf("%d", 0);
15+
}
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// CIR-DEVICE: cir.func @_Z7printerv() extra({{.*}}) {
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// CIR-DEVICE: %[[#Packed:]] = cir.alloca !ty_anon_struct
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// CIR-DEVICE: %[[#Zero:]] = cir.const #cir.int<0> : !s32i loc(#loc5)
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// CIR-DEVICE: %[[#Field0:]] = cir.get_member %0[0]
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// CIR-DEVICE: cir.store align(4) %[[#Zero]], %[[#Field0]]
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// CIR-DEVICE: %[[#Output:]] = cir.cast(bitcast, %[[#Packed]] : !cir.ptr<!ty_anon_struct>)
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// CIR-DEVICE: cir.call @vprintf(%{{.+}}, %[[#Output]])
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// CIR-DEVICE: cir.return
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// CIR-DEVICE: }
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// LLVM-DEVICE: define dso_local void @_Z7printerv() {{.*}} {
28+
// LLVM-DEVICE: %[[#LLVMPacked:]] = alloca { i32 }, i64 1, align 8
29+
// LLVM-DEVICE: %[[#LLVMField0:]] = getelementptr { i32 }, ptr %[[#LLVMPacked]], i32 0, i32 0
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// LLVM-DEVICE: store i32 0, ptr %[[#LLVMField0]], align 4
31+
// LLVM-DEVICE: call i32 @vprintf(ptr @.str, ptr %[[#LLVMPacked]])
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// LLVM-DEVICE: ret void
33+
// LLVM-DEVICE: }
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35+
__device__ void no_extra() {
36+
printf("hello world");
37+
}
38+
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// CIR-DEVICE: cir.func @_Z8no_extrav() extra(#fn_attr) {
40+
// CIR-DEVICE: %[[#NULLPTR:]] = cir.const #cir.ptr<null>
41+
// CIR-DEVICE: cir.call @vprintf(%{{.+}}, %[[#NULLPTR]])
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// CIR-DEVICE: cir.return
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// CIR-DEVICE: }
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// LLVM-DEVICE: define dso_local void @_Z8no_extrav() {{.*}} {
46+
// LLVM-DEVICE: call i32 @vprintf(ptr @.str.1, ptr null)
47+
// LLVM-DEVICE: ret void
48+
// LLVM-DEVICE: }

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