dmd/argtypes.h

@@ -21,5 +21,7 @@ namespace dmd
     TypeTuple *toArgTypes_sysv_x64(Type *t);
     // in argtypes_aarch64.d
     TypeTuple *toArgTypes_aarch64(Type *t);
+    // in argtypes_s390x.d
+    TypeTuple *toArgTypes_s390x(Type *t);
     bool isHFVA(Type *t, int maxNumElements = 4, Type **rewriteType = nullptr);
 }

dmd/argtypes_s390x.d

@@ -0,0 +1,74 @@
+/**
+ * Break down a D type into basic (register) types for the IBM Z ELF ABI.
+ *
+ * Copyright:   Copyright (C) 2024-2025 by The D Language Foundation, All Rights Reserved
+ * Authors:     Martin Kinkelin
+ * License:     $(LINK2 https://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
+ * Source:      $(LINK2 https://github.com/dlang/dmd/blob/master/src/dmd/argtypes_s390x.d, _argtypes_s390x.d)
+ * Documentation:  https://dlang.org/phobos/dmd_argtypes_s390x.html
+ * Coverage:    https://codecov.io/gh/dlang/dmd/src/master/src/dmd/argtypes_s390x.d
+ */
+
+module dmd.argtypes_s390x;
+
+import dmd.astenums;
+import dmd.mtype;
+import dmd.typesem;
+
+/****************************************************
+ * This breaks a type down into 'simpler' types that can be passed to a function
+ * in registers, and returned in registers.
+ * This is the implementation for the IBM Z ELF ABI,
+ * based on https://github.com/IBM/s390x-abi/releases/download/v1.6/lzsabi_s390x.pdf.
+ * Params:
+ *      t = type to break down
+ * Returns:
+ *      tuple of types, each element can be passed in a register.
+ *      A tuple of zero length means the type cannot be passed/returned in registers.
+ *      null indicates a `void`.
+ */
+TypeTuple toArgTypes_s390x(Type t)
+{
+    if (t == Type.terror)
+        return new TypeTuple(t);
+
+    const size = cast(size_t) t.size();
+    if (size == 0)
+        return null;
+
+    // TODO
+    // Implement the rest of the va args passing
+    //...
+    Type tb = t.toBasetype();
+    const isAggregate = tb.ty == Tstruct || tb.ty == Tsarray || tb.ty == Tarray || tb.ty == Tdelegate || tb.iscomplex();
+    if (!isAggregate)
+        return new TypeTuple(t);
+    // unwrap single-float struct per ABI requirements
+    if (auto tstruct = t.isTypeStruct())
+    {
+        if (tstruct.sym.fields.length == 1)
+        {
+            Type fieldType = tstruct.sym.fields[0].type.toBasetype();
+            if (fieldType.isfloating())
+            {
+                return new TypeTuple(fieldType);
+            }
+        }
+    }
+
+    // pass remaining aggregates in 1 or 2 GP registers
+    static Type getGPType(size_t size)
+    {
+        switch (size)
+        {
+        case 1:  return Type.tint8;
+        case 2:  return Type.tint16;
+        case 4:  return Type.tint32;
+        case 8:  return Type.tint64;
+        default:
+            import dmd.typesem : sarrayOf;
+            return Type.tint64.sarrayOf((size + 7) / 8);
+        }
+    }
+    return new TypeTuple(getGPType(size));
+}

dmd/cxxfrontend.d

@@ -698,4 +698,13 @@ version (IN_LLVM)
         import dmd.argtypes_x86;
         return dmd.argtypes_x86.toArgTypes_x86(t);
     }
+
+    /***********************************************************
+     * argtypes_s390x.d
+     */
+    TypeTuple toArgTypes_s390x(Type t)
+    {
+        import dmd.argtypes_s390x;
+        return dmd.argtypes_s390x.toArgTypes_s390x(t);
+    }
 }

gen/target.cpp

@@ -258,6 +258,8 @@ TypeTuple *Target::toArgTypes(Type *t) {
     return toArgTypes_sysv_x64(t);
   if (arch == llvm::Triple::aarch64 || arch == llvm::Triple::aarch64_be)
     return toArgTypes_aarch64(t);
+  if (arch == llvm::Triple::systemz)
+    return toArgTypes_s390x(t);
   return nullptr;
 }
 

runtime/druntime/src/core/internal/vararg/s390x.d

@@ -26,7 +26,7 @@ T va_arg(T)(va_list ap)
 {
     static if (is(T U == __argTypes))
     {
-        static if (U.length == 0 || U[0].sizeof > 8 || is(T1 == __vector))
+        static if (U.length == 0 || U[0].sizeof > 8 || is(U[0] == __vector))
         {
             // Always passed in memory (varying vectors are passed in parameter area)
             auto p = *cast(T*) ap.__overflow_arg_area;
@@ -45,7 +45,7 @@ T va_arg(T)(va_list ap)
                     // Passed in $fr registers (FPR region starts at +0x80)
                     auto p = cast(T*) ap.__reg_save_area + 128 + ap.__fpr * 8;
                     ap.__fpr++;
-                    return p;
+                    return *p;
                 }
                 else
                 {
@@ -54,7 +54,7 @@ T va_arg(T)(va_list ap)
                     // no matter the actual size of the fp variable
                     // parameter slot is always 8-byte-wide (f32 is extended to f64)
                     ap.__overflow_arg_area += 8;
-                    return p;
+                    return *p;
                 }
             }
             else
@@ -65,7 +65,7 @@ T va_arg(T)(va_list ap)
                     // Passed in $gpr registers (GPR region starts at +0x10)
                     auto p = cast(T*) ap.__reg_save_area + 16 + ap.__gpr * 8;
                     ap.__gpr++;
-                    return p;
+                    return *p;
                 }
                 else
                 {
@@ -74,7 +74,7 @@ T va_arg(T)(va_list ap)
                     // no matter the actual size of the gpr variable
                     // parameter slot is always 8-byte-wide (after ABI adjustments)
                     ap.__overflow_arg_area += 8;
-                    return p;
+                    return *p;
                 }
             }
         }
@@ -93,6 +93,23 @@ T va_arg(T)(va_list ap)
 void va_arg()(va_list ap, TypeInfo ti, void* parmn)
 {
     TypeInfo arg1, arg2;
+    if (TypeInfo_Struct ti_struct = cast(TypeInfo_Struct) ti)
+    {
+        // handle single-float element struct
+        const rtFields = ti_struct.offTi();
+        if (rtFields && rtFields.length == 1)
+        {
+            TypeInfo field1TypeInfo = rtFields[0].ti;
+            if (field1TypeInfo is typeid(float) || field1TypeInfo is typeid(double))
+            {
+                auto tsize = field1TypeInfo.tsize;
+                auto toffset = rtFields[0].offset;
+                parmn[0..tsize] = p[toffset..tsize];
+                return;
+            }
+        }
+    }
+
     if (!ti.argTypes(arg1, arg2))
     {
         TypeInfo_Vector v1 = arg1 ? cast(TypeInfo_Vector) arg1 : null;
@@ -117,6 +134,30 @@ void va_arg()(va_list ap, TypeInfo ti, void* parmn)
                 parmn[0..tsize] = p[0..tsize];
             }
         }
+        else if (arg1 && (arg1 is typeid(float) || arg1 is typeid(double)))
+        {
+            // Maybe passed in $fr registers
+            if (ap.__fpr <= 4)
+            {
+                // Passed in $fr registers (FPR region starts at +0x80)
+                auto p = cast(T*) ap.__reg_save_area + 128 + ap.__fpr * 8;
+                ap.__fpr++;
+                parmn[0..tsize] = p[0..tsize];
+            }
+            else
+            {
+                // overflow arguments
+                auto p = cast(T*) ap.__overflow_arg_area;
+                // no matter the actual size of the fp variable
+                // parameter slot is always 8-byte-wide (f32 is extended to f64)
+                ap.__overflow_arg_area += 8;
+                parmn[0..tsize] = p[0..tsize];
+            }
+        }
+        else
+        {
+            assert(false, "unhandled va_arg type!");
+        }
         assert(!arg2);
     }
     else

runtime/druntime/src/core/threadasm.S

@@ -771,15 +771,15 @@ fiber_switchContext:
     std     %f15, 56(%r1)
     .cfi_offset 31, -168
     /* Save stack pointer */
-    la      %r0, 224(%r15)
+    la      %r0, 168(%r15)
     stg     %r0, 0(%r2)
 
     /* Load the new context pointer as stack pointer.  */
     lgr     %r15, %r3
-    .cfi_def_cfa 3, 160
+    .cfi_def_cfa 3, 216
     /* Store the new stack pointer location to the parameter area */
     stg     %r15, 120(%r15)
-    aghi    %r15, -224
+    aghi    %r15, -168
     .cfi_def_cfa 15, 384
 
     /* Restore call-saved floating point registers.  */