Implement bitcast for 64-bit date type (#5895)

Close #5470

* implement bitcast for 64-bit date type
* Move 'ensurePrelude' to base class to remove duplication
* Assert on 'double' type for Metal target, as Metal doesn't have 'double' support

8 files changed, 73 insertions, 42 deletions

diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index f38adc67e..b70069d42 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -5137,4 +5137,15 @@ void CLikeSourceEmitter::emitModuleImpl(IRModule* module, DiagnosticSink* sink)
     executeEmitActions(actions);
 }
 
+void CLikeSourceEmitter::ensurePrelude(const char* preludeText)
+{
+    IRStringLit* stringLit;
+    if (!m_builtinPreludes.tryGetValue(preludeText, stringLit))
+    {
+        IRBuilder builder(m_irModule);
+        stringLit = builder.getStringValue(UnownedStringSlice(preludeText));
+        m_builtinPreludes[preludeText] = stringLit;
+    }
+    m_requiredPreludes.add(stringLit);
+}
 } // namespace Slang
diff --git a/source/slang/slang-emit-c-like.h b/source/slang/slang-emit-c-like.h
index 7f6f32923..dd8e27674 100644
--- a/source/slang/slang-emit-c-like.h
+++ b/source/slang/slang-emit-c-like.h
@@ -678,6 +678,9 @@ protected:
 
     String _emitLiteralOneWithType(int bitWidth);
 
+
+    virtual void ensurePrelude(const char* preludeText);
+
     CodeGenContext* m_codeGenContext = nullptr;
     IRModule* m_irModule = nullptr;
 
@@ -723,6 +726,8 @@ protected:
     {
         String requireComputeDerivatives;
     } m_requiredAfter;
+
+    Dictionary<const char*, IRStringLit*> m_builtinPreludes;
 };
 
 } // namespace Slang
diff --git a/source/slang/slang-emit-glsl.cpp b/source/slang/slang-emit-glsl.cpp
index 2c2447c53..d6f3795e3 100644
--- a/source/slang/slang-emit-glsl.cpp
+++ b/source/slang/slang-emit-glsl.cpp
@@ -2030,6 +2030,32 @@ bool GLSLSourceEmitter::tryEmitInstExprImpl(IRInst* inst, const EmitOpInfo& inOu
                     emitType(inst->getDataType());
                 }
                 break;
+            case BaseType::Int64:
+                if (fromType == BaseType::Double)
+                {
+                    m_writer->emit("int64_t(doubleBitsToInt64(");
+                    emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
+                    m_writer->emit("))");
+                    return true;
+                }
+                else
+                {
+                    emitType(inst->getDataType());
+                }
+                break;
+            case BaseType::UInt64:
+                if (fromType == BaseType::Double)
+                {
+                    m_writer->emit("uint64_t(doubleBitsToUint64(");
+                    emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
+                    m_writer->emit("))");
+                    return true;
+                }
+                else
+                {
+                    emitType(inst->getDataType());
+                }
+                break;
             case BaseType::Half:
                 switch (fromType)
                 {
diff --git a/source/slang/slang-emit-hlsl.cpp b/source/slang/slang-emit-hlsl.cpp
index 824680b72..c43f075b2 100644
--- a/source/slang/slang-emit-hlsl.cpp
+++ b/source/slang/slang-emit-hlsl.cpp
@@ -11,6 +11,23 @@
 namespace Slang
 {
 
+static const char* kHLSLBuiltInPrelude64BitCast = R"(
+uint64_t _slang_asuint64(double x)
+{
+    uint32_t low;
+    uint32_t high;
+    asuint(x, low, high);
+    return ((uint64_t)high << 32) | low;
+}
+
+double _slang_asdouble(uint64_t x)
+{
+    uint32_t low = x & 0xFFFFFFFF;
+    uint32_t high = x >> 32;
+    return asdouble(low, high);
+}
+)";
+
 void HLSLSourceEmitter::_emitHLSLDecorationSingleString(
     const char* name,
     IRFunc* entryPoint,
@@ -822,17 +839,12 @@ bool HLSLSourceEmitter::tryEmitInstExprImpl(IRInst* inst, const EmitOpInfo& inOu
                 //
                 // There is no current function (it seems)
                 // for bit-casting an `int16_t` to a `half`.
-                //
-                // TODO: There is an `asdouble` function
-                // for converting two 32-bit integer values into
-                // one `double`. We could use that for
-                // bit casts of 64-bit values with a bit of
-                // extra work, but doing so might be best
-                // handled in an IR pass that legalizes
-                // bit-casts.
-                //
                 m_writer->emit("asfloat");
                 break;
+            case BaseType::Double:
+                ensurePrelude(kHLSLBuiltInPrelude64BitCast);
+                m_writer->emit("_slang_asdouble");
+                break;
             }
             m_writer->emit("(");
             int closeCount = 1;
@@ -844,6 +856,8 @@ bool HLSLSourceEmitter::tryEmitInstExprImpl(IRInst* inst, const EmitOpInfo& inOu
                 diagnoseUnhandledInst(inst);
                 break;
 
+            case BaseType::Int64:
+            case BaseType::UInt64:
             case BaseType::UInt:
             case BaseType::Int:
             case BaseType::Bool:
@@ -860,6 +874,11 @@ bool HLSLSourceEmitter::tryEmitInstExprImpl(IRInst* inst, const EmitOpInfo& inOu
                 m_writer->emit("asuint16(");
                 closeCount++;
                 break;
+            case BaseType::Double:
+                ensurePrelude(kHLSLBuiltInPrelude64BitCast);
+                m_writer->emit("_slang_asuint64(");
+                closeCount++;
+                break;
             }
 
             emitOperand(inst->getOperand(0), getInfo(EmitOp::General));
diff --git a/source/slang/slang-emit-metal.cpp b/source/slang/slang-emit-metal.cpp
index 45a9e60ad..282d8f95c 100644
--- a/source/slang/slang-emit-metal.cpp
+++ b/source/slang/slang-emit-metal.cpp
@@ -263,18 +263,6 @@ void MetalSourceEmitter::emitEntryPointAttributesImpl(
     }
 }
 
-void MetalSourceEmitter::ensurePrelude(const char* preludeText)
-{
-    IRStringLit* stringLit;
-    if (!m_builtinPreludes.tryGetValue(preludeText, stringLit))
-    {
-        IRBuilder builder(m_irModule);
-        stringLit = builder.getStringValue(UnownedStringSlice(preludeText));
-        m_builtinPreludes[preludeText] = stringLit;
-    }
-    m_requiredPreludes.add(stringLit);
-}
-
 void MetalSourceEmitter::emitMemoryOrderOperand(IRInst* inst)
 {
     auto memoryOrder = (IRMemoryOrder)getIntVal(inst);
@@ -1065,7 +1053,6 @@ void MetalSourceEmitter::emitSimpleTypeImpl(IRType* type)
     case kIROp_UInt8Type:
     case kIROp_UIntType:
     case kIROp_FloatType:
-    case kIROp_DoubleType:
     case kIROp_HalfType:
         {
             m_writer->emit(getDefaultBuiltinTypeName(type->getOp()));
@@ -1093,6 +1080,9 @@ void MetalSourceEmitter::emitSimpleTypeImpl(IRType* type)
         m_writer->emit(getName(type));
         return;
 
+    case kIROp_DoubleType:
+        SLANG_UNEXPECTED("'double' type emitted");
+        return;
     case kIROp_VectorType:
         {
             auto vecType = (IRVectorType*)type;
diff --git a/source/slang/slang-emit-metal.h b/source/slang/slang-emit-metal.h
index 17562b1c4..b67a5b801 100644
--- a/source/slang/slang-emit-metal.h
+++ b/source/slang/slang-emit-metal.h
@@ -22,13 +22,9 @@ public:
 
     virtual RefObject* getExtensionTracker() SLANG_OVERRIDE { return m_extensionTracker; }
 
-    Dictionary<const char*, IRStringLit*> m_builtinPreludes;
-
 protected:
     RefPtr<MetalExtensionTracker> m_extensionTracker;
 
-    void ensurePrelude(const char* preludeText);
-
     void emitMemoryOrderOperand(IRInst* inst);
     virtual void emitParameterGroupImpl(IRGlobalParam* varDecl, IRUniformParameterGroupType* type)
         SLANG_OVERRIDE;
diff --git a/source/slang/slang-emit-wgsl.cpp b/source/slang/slang-emit-wgsl.cpp
index 0e45fd4cf..da5e38327 100644
--- a/source/slang/slang-emit-wgsl.cpp
+++ b/source/slang/slang-emit-wgsl.cpp
@@ -49,18 +49,6 @@ fn _slang_getNan() -> f32
 }
 )";
 
-void WGSLSourceEmitter::ensurePrelude(const char* preludeText)
-{
-    IRStringLit* stringLit;
-    if (!m_builtinPreludes.tryGetValue(preludeText, stringLit))
-    {
-        IRBuilder builder(m_irModule);
-        stringLit = builder.getStringValue(UnownedStringSlice(preludeText));
-        m_builtinPreludes[preludeText] = stringLit;
-    }
-    m_requiredPreludes.add(stringLit);
-}
-
 void WGSLSourceEmitter::emitSwitchCaseSelectorsImpl(
     const SwitchRegion::Case* const currentCase,
     const bool isDefault)
diff --git a/source/slang/slang-emit-wgsl.h b/source/slang/slang-emit-wgsl.h
index 28311aa27..390ee876d 100644
--- a/source/slang/slang-emit-wgsl.h
+++ b/source/slang/slang-emit-wgsl.h
@@ -57,10 +57,6 @@ public:
     void emit(const AddressSpace addressSpace);
 
     virtual bool shouldFoldInstIntoUseSites(IRInst* inst) SLANG_OVERRIDE;
-    Dictionary<const char*, IRStringLit*> m_builtinPreludes;
-
-protected:
-    void ensurePrelude(const char* preludeText);
 
 private:
     bool maybeEmitSystemSemantic(IRInst* inst);