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[FFI/JDK21] Enable the union support in JDK21 #18291

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Nov 1, 2023
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[FFI/JDK21] Enable the union support in JDK21 #18291

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191 changes: 157 additions & 34 deletions jcl/src/java.base/share/classes/openj9/internal/foreign/abi/LayoutStrPreprocessor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,10 @@
import java.lang.foreign.MemorySegment;
import java.lang.foreign.PaddingLayout;
import java.lang.foreign.SequenceLayout;
import java.lang.foreign.StructLayout;
import java.lang.foreign.UnionLayout;
import java.lang.foreign.ValueLayout;
import static java.lang.foreign.ValueLayout.*;
import jdk.internal.foreign.abi.LinkerOptions;
/*[ELSE] JAVA_SPEC_VERSION >= 21 */
import jdk.incubator.foreign.CLinker.TypeKind;
Expand All @@ -51,16 +54,17 @@
*/
@SuppressWarnings("nls")
final class LayoutStrPreprocessor {
private static final String osName = System.getProperty("os.name").toLowerCase();
private static final String arch = System.getProperty("os.arch").toLowerCase();
private static final boolean isX86_64 = arch.equals("amd64") || arch.equals("x86_64");
private static final boolean isLinuxS390x = arch.equals("s390x") && osName.startsWith("linux");

/*[IF JAVA_SPEC_VERSION == 17]*/
private static final String VARARGS_ATTR_NAME;

static {
final String osName = System.getProperty("os.name").toLowerCase();
final String arch = System.getProperty("os.arch").toLowerCase();

/* Note: the attributes intended for the layout with variadic argument are defined in OpenJDK. */
if ((arch.equals("amd64") || arch.equals("x86_64"))) {
if (isX86_64) {
if (osName.startsWith("windows")) {
VARARGS_ATTR_NAME = "abi/windows/varargs";
} else {
Expand All @@ -78,7 +82,7 @@ final class LayoutStrPreprocessor {
} else {
VARARGS_ATTR_NAME = "abi/ppc64/aix/varargs";
}
} else if (arch.equals("s390x") && osName.startsWith("linux")) {
} else if (isLinuxS390x) {
VARARGS_ATTR_NAME = "abi/s390x/sysv/varargs";
} else {
throw new InternalError("Unsupported platform: " + arch + "_" + osName);
Expand Down Expand Up @@ -133,7 +137,12 @@ static String getSimplifiedLayoutString(MemoryLayout targetLayout, boolean isDow
private static long getTotalPaddingBytesOfStruct(MemoryLayout targetLayout) {
long paddingBytes = 0;

if (targetLayout instanceof GroupLayout structLayout) {
/*[IF JAVA_SPEC_VERSION >= 21]*/
if (targetLayout instanceof StructLayout structLayout)
/*[ELSE] JAVA_SPEC_VERSION >= 21 */
if (targetLayout instanceof GroupLayout structLayout)
/*[ENDIF] JAVA_SPEC_VERSION >= 21 */
{
List<MemoryLayout> elementLayoutList = structLayout.memberLayouts();
for (MemoryLayout structElement : elementLayoutList) {
if (isPaddingLayout(structElement)) {
Expand Down Expand Up @@ -190,15 +199,15 @@ private static long getTotalPaddingBytesOfStruct(MemoryLayout targetLayout) {
*
* Note:
* The prefix "ByteSize#CountOfElmemnt" and "#CountOfElmemnt" are not required in
* the upcall given the converted layout stirngs are further parsed for the generated
* the upcall given the converted layout strings are further parsed for the generated
* thunk in native, which is logically different from downcall.
*/
private static StringBuilder preprocessLayout(MemoryLayout targetLayout, boolean isDownCall) {
StringBuilder targetLayoutString = new StringBuilder("");
StringBuilder targetLayoutStr = new StringBuilder();

/* Directly obtain the kind symbol of the primitive layout. */
if (targetLayout instanceof ValueLayout valueLayout) {
targetLayoutString.append(getPrimitiveTypeSymbol(valueLayout));
targetLayoutStr.append(getPrimitiveTypeSymbol(valueLayout));
} else if (targetLayout instanceof SequenceLayout arrayLayout) { /* Intended for nested arrays. */
MemoryLayout elementLayout = arrayLayout.elementLayout();
/*[IF JAVA_SPEC_VERSION >= 21]*/
Expand All @@ -209,38 +218,152 @@ private static StringBuilder preprocessLayout(MemoryLayout targetLayout, boolean

/* The padding bytes is required in the native signature for upcall thunk generation. */
if (isPaddingLayout(elementLayout) && !isDownCall) {
targetLayoutString.append('(').append(arrayLayout.byteSize()).append(')');
targetLayoutStr.append('(').append(arrayLayout.byteSize()).append(')');
} else {
targetLayoutString.append(elementCount).append(':').append(preprocessLayout(elementLayout, isDownCall));
targetLayoutStr.append(elementCount).append(':').append(preprocessLayout(elementLayout, isDownCall));
}
} else if (targetLayout instanceof GroupLayout structLayout) { /* Intended for the nested structs. */
List<MemoryLayout> elementLayoutList = structLayout.memberLayouts();
int structElementCount = elementLayoutList.size();
StringBuilder elementLayoutStrs = new StringBuilder("");
int paddingElements = 0;
for (int elemIndex = 0; elemIndex < structElementCount; elemIndex++) {
MemoryLayout structElement = elementLayoutList.get(elemIndex);
/* Ignore any padding element in the struct as it is handled by ffi_call by default. */
if (isPaddingLayout(structElement)) {
paddingElements += 1;
/* The padding bytes is required in the native signature for upcall thunk generation. */
if (!isDownCall) {
elementLayoutStrs.append('(').append(structElement.byteSize()).append(')');
}
} else {
elementLayoutStrs.append(preprocessLayout(structElement, isDownCall));
/*[IF JAVA_SPEC_VERSION >= 21]*/
} else if (targetLayout instanceof UnionLayout unionLayout) { /* Intended for the nested union since JDK21. */
targetLayoutStr = encodeUnionLayoutStr(unionLayout, targetLayoutStr, isDownCall);
/*[ENDIF] JAVA_SPEC_VERSION >= 21 */
} else if (targetLayout instanceof GroupLayout groupLayout) { /* Intended for the nested struct. */
targetLayoutStr = encodeStructLayoutStr(groupLayout, targetLayoutStr, isDownCall);
}

return targetLayoutStr;
}

/* Encode the types in the struct layout to a symbol string to simplify the further processing in native. */
private static StringBuilder encodeStructLayoutStr(GroupLayout structLayout, StringBuilder targetLayoutStr, boolean isDownCall) {
List<MemoryLayout> elementLayoutList = structLayout.memberLayouts();
int structElementCount = elementLayoutList.size();
StringBuilder elementLayoutStrs = new StringBuilder();
int paddingElements = 0;

for (MemoryLayout structElement : elementLayoutList) {
/* Ignore any padding element in the struct as it is handled by ffi_call by default. */
if (isPaddingLayout(structElement)) {
paddingElements += 1;
/* The padding bytes is required in the native signature for upcall thunk generation. */
if (!isDownCall) {
elementLayoutStrs.append('(').append(structElement.byteSize()).append(')');
}
} else {
elementLayoutStrs.append(preprocessLayout(structElement, isDownCall));
}
/* Prefix "#" to denote the start of this layout string in the case of downcall. */
if (isDownCall) {
targetLayoutString.append('#').append(structElementCount - paddingElements);
}

/* Prefix "#" to denote the start of this layout string in the case of downcall. */
if (isDownCall) {
targetLayoutStr.append('#').append(structElementCount - paddingElements);
}
targetLayoutStr.append('[').append(elementLayoutStrs).append(']');

return targetLayoutStr;
}

/*[IF JAVA_SPEC_VERSION >= 21]*/
/* Encode the types in the union layout to a symbol string to simplify the further processing in native. */
private static StringBuilder encodeUnionLayoutStr(UnionLayout unionLayout, StringBuilder targetLayoutStr, boolean isDownCall) {
long unionByteSize = unionLayout.byteSize();
StringBuilder elementLayoutStrs = new StringBuilder();
int byteAlignment = (int)unionLayout.byteAlignment();
ValueLayout sequenceElement;

/* The idea is to select the primitive type with the biggest alignment of the union
* (obtained via unionLayout.byteAlignment()) to be laid out as a sequence which is
* correctly mappped onto the given GPRs/FPRs/stack on the hardware.
*/
switch (byteAlignment) {
case 1: /* 1 Byte. */
sequenceElement = JAVA_BYTE;
break;
case 2: /* 2 Bytes. */
sequenceElement = JAVA_SHORT;
break;
case 4: /* 4 Bytes. */
if (validatePrimTypesOfUnionForGPROrStack(unionLayout, byteAlignment)) {
sequenceElement = JAVA_INT;
} else {
sequenceElement = JAVA_FLOAT;
}
break;
case 8: /* 8 Bytes. */
if (validatePrimTypesOfUnionForGPROrStack(unionLayout, byteAlignment)) {
sequenceElement = JAVA_LONG;
} else {
sequenceElement = JAVA_DOUBLE;
}
targetLayoutString.append('[').append(elementLayoutStrs).append(']');
break;
default:
throw new IllegalArgumentException("Invalid alignment of the union layout: " + unionLayout);
}

long elementByteSize = sequenceElement.byteSize();
long sequenceCount = (unionByteSize / elementByteSize)
+ ((0 == (unionByteSize % elementByteSize)) ? 0 : 1);

/* There is no need to create a sequence layout for a single element. */
MemoryLayout sequenceLayout = (sequenceCount != 1)
? MemoryLayout.sequenceLayout(sequenceCount, sequenceElement)
: sequenceElement;
elementLayoutStrs.append(preprocessLayout(sequenceLayout, isDownCall));

/* Prefix "#" to denote the start of this layout string in the case of downcall. */
if (isDownCall) {
targetLayoutStr.append('#').append(1);
}
targetLayoutStr.append('[').append(elementLayoutStrs).append(']');

return targetLayoutString;
return targetLayoutStr;
}

/* Check whether the specified 4/8-byte aligned group layout (struct/union) layout contains
* non-floating-point primitives so as to determine whether the elements of union can be safely
* mapped to GPRs/stack which is uniquely determined by the underlying libffi/compiler.
*/
private static boolean validatePrimTypesOfUnionForGPROrStack(GroupLayout groupLayout, int byteAlignment) {
List<MemoryLayout> elementLayoutList = groupLayout.memberLayouts();
boolean arePrimTypesForGPROrStack = false;
for (MemoryLayout elementLayout : elementLayoutList) {
if (((elementLayout instanceof ValueLayout elemValueLayout)
&& validatePrimTypeForGPROrStack(elemValueLayout, byteAlignment))
|| ((elementLayout instanceof GroupLayout elemGroupLayout)
&& validatePrimTypesOfUnionForGPROrStack(elemGroupLayout, byteAlignment))
) {
arePrimTypesForGPROrStack = true;
break;
}
}

return arePrimTypesForGPROrStack;
}

/* Check whether the primitive type can be safely mappped to GPR/stack when it is not float/double
* in the struct/union including some exceptions due to the platform restrictions.
*
* Note:
* The primitive type is mappped to GPR/stack as long as it is not float/double on most platforms
* with a couple of exceptions that:
* 1) the biggest alignment is 8 bytes on the non-X86_64 platforms even though the type is float.
* 2) it is always mapped onto GPR/stack in any case on zLinux.
*/
private static boolean validatePrimTypeForGPROrStack(ValueLayout primLayout, int byteAlignment) {
Class<?> carrier = primLayout.carrier();
boolean isPrimTypeForGPROrStack;

if (carrier == float.class) {
isPrimTypeForGPROrStack = isLinuxS390x || ((8 == byteAlignment) && !isX86_64);
} else if (carrier == double.class) {
isPrimTypeForGPROrStack = isLinuxS390x;
} else {
isPrimTypeForGPROrStack = true;
}

return isPrimTypeForGPROrStack;
}
/*[ENDIF] JAVA_SPEC_VERSION >= 21 */

/* Determine whether the specfied layout is a padding layout or not. */
private static boolean isPaddingLayout(MemoryLayout targetLayout) {
/*[IF JAVA_SPEC_VERSION >= 21]*/
Expand All @@ -254,7 +377,7 @@ private static boolean isPaddingLayout(MemoryLayout targetLayout) {
/*[IF JAVA_SPEC_VERSION >= 21]*/
private static String getPrimitiveTypeSymbol(ValueLayout targetLayout) {
Class<?> javaType = targetLayout.carrier();
String typeSymbol = "";
String typeSymbol;

if (javaType == byte.class) {
/* JAVA_BYTE corresponds to C_CHAR (1 byte) in native. */
Expand All @@ -281,7 +404,7 @@ private static String getPrimitiveTypeSymbol(ValueLayout targetLayout) {
*/
TypeKind kind = (TypeKind)targetLayout.attribute(TypeKind.ATTR_NAME)
.orElseThrow(() -> new IllegalArgumentException("The layout's ABI class is empty"));
String typeSymbol = "";
String typeSymbol;

switch (kind) {
case CHAR:
Expand Down
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