Add support for extracting a Value from a ValueAsMetadata.

Author: maleadt

deps/LLVMExtra/include/LLVMExtra.h

@@ -153,6 +153,7 @@ LLVMValueRef LLVMBuildCallWithOpBundle(LLVMBuilderRef B, LLVMValueRef Fn,
                                        LLVMValueRef *Args, unsigned NumArgs,
                                        LLVMOperandBundleDefRef *Bundles, unsigned NumBundles,
                                        const char *Name);
+LLVMValueRef LLVMMetadataAsValue2(LLVMContextRef C, LLVMMetadataRef Metadata);
 
 LLVM_C_EXTERN_C_END
 #endif

deps/LLVMExtra/lib/llvm-api.cpp

@@ -518,3 +518,11 @@ LLVMValueRef LLVMBuildCallWithOpBundle(LLVMBuilderRef B, LLVMValueRef Fn,
     return wrap(unwrap(B)->CreateCall(FnT, unwrap(Fn), makeArrayRef(unwrap(Args), NumArgs),
                                       BundleArray, Name));
 }
+
+LLVMValueRef LLVMMetadataAsValue2(LLVMContextRef C, LLVMMetadataRef Metadata) {
+  auto *MD = unwrap(Metadata);
+  if (auto *VAM = dyn_cast<ValueAsMetadata>(MD))
+    return wrap(VAM->getValue());
+  else
+    return wrap(MetadataAsValue::get(*unwrap(C), MD));
+}

lib/libLLVM_extra.jl

@@ -395,3 +395,6 @@ function LLVMBuildCallWithOpBundle(B, Fn, Args, NumArgs, Bundles, NumBundles, Na
     ccall((:LLVMBuildCallWithOpBundle, libLLVMExtra), LLVMValueRef, (LLVMBuilderRef, LLVMValueRef, Ptr{LLVMValueRef}, Cuint, Ptr{LLVMOperandBundleDefRef}, Cuint, Cstring), B, Fn, Args, NumArgs, Bundles, NumBundles, Name)
 end
 
+function LLVMMetadataAsValue2(C, MD)
+    ccall((:LLVMMetadataAsValue2, libLLVMExtra), LLVMValueRef, (LLVMContextRef, LLVMMetadataRef), C, MD)
+end

src/core/metadata.jl

@@ -48,7 +48,11 @@ end
 end
 register(MetadataAsValue, API.LLVMMetadataAsValueValueKind)
 
-Value(md::Metadata; ctx::Context) = MetadataAsValue(API.LLVMMetadataAsValue(ctx, md))
+# NOTE: this can be used to both pack e.g. metadata as a value, and to extract the
+#       value from an ValueAsMetadata, so we don't type-assert narrowly here
+Value(md::Metadata; ctx::Context) = Value(API.LLVMMetadataAsValue2(ctx, md))
+
+Base.convert(T::Type{<:Value}, val::Metadata) = Value(val)::T
 
 # NOTE: we can't do this automatically, as we can't query the context of metadata...
 #       add wrappers to do so? would also simplify, e.g., `string(::MDString)`
@@ -72,7 +76,7 @@ register(LocalAsMetadata, API.LLVMLocalAsMetadataMetadataKind)
 #       metadata from an MetadataAsValue, so we don't type-assert narrowly here
 Metadata(val::Value) = Metadata(API.LLVMValueAsMetadata(val))
 
-Base.convert(::Type{Metadata}, val::Value) = Metadata(val)
+Base.convert(T::Type{<:Metadata}, val::Value) = Metadata(val)::T
 
 
 ## values

test/core.jl

@@ -779,6 +779,33 @@ end
 Context() do ctx
     str = MDString("foo"; ctx)
     @test string(str) == "foo"
+
+    # wrap as Value
+    val = Value(str; ctx)
+    @test val isa LLVM.MetadataAsValue
+
+    # back to Metadata
+    md = Metadata(val)
+    @test md == str
+
+    # more specific conversion
+    @test convert(MDString, val) == str
+end
+
+Context() do ctx
+    int = ConstantInt(42; ctx)
+    @test convert(Int, int) == 42
+
+    # wrap as Metadata
+    md = Metadata(int)
+    @test md isa LLVM.ValueAsMetadata
+
+    # back to Value
+    val = Value(md; ctx)
+    @test val == int
+
+    # more specific conversion
+    @test convert(ConstantInt, val) == int
 end
 
 Context() do ctx