interp: don't copy unknown values in runtime.sliceCopy

This was bug https://github.com/tinygo-org/tinygo/issues/3890.
See the diff for details. Essentially, it means that `copy` in the
interpreter was copying data that wasn't known yet, or copying data into
a slice that could be read externally after the interp pass.

interp/interpreter.go

@@ -338,6 +338,20 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 					if err != nil {
 						return nil, mem, r.errorAt(inst, err)
 					}
+					if mem.hasExternalStore(src) || mem.hasExternalLoadOrStore(dst) {
+						// These are the same checks as there are on llvm.Load
+						// and llvm.Store in the interpreter. Copying is
+						// essentially loading from the source array and storing
+						// to the destination array, hence why we need to do the
+						// same checks here.
+						// This fixes the following bug:
+						// https://github.com/tinygo-org/tinygo/issues/3890
+						err := r.runAtRuntime(fn, inst, locals, &mem, indent)
+						if err != nil {
+							return nil, mem, err
+						}
+						continue
+					}
 					nBytes := uint32(n * elemSize)
 					dstObj := mem.getWritable(dst.index())
 					dstBuf := dstObj.buffer.asRawValue(r)

interp/testdata/slice-copy.ll

@@ -7,6 +7,10 @@ target triple = "x86_64--linux"
 @main.int16SliceSrc.buf = internal global [3 x i16] [i16 5, i16 123, i16 1024]
 @main.int16SliceSrc = internal unnamed_addr global { ptr, i64, i64 } { ptr @main.int16SliceSrc.buf, i64 3, i64 3 }
 @main.int16SliceDst = internal unnamed_addr global { ptr, i64, i64 } zeroinitializer
+@main.sliceSrcUntaint.buf = internal global [2 x i8] c"ab"
+@main.sliceDstUntaint.buf = internal global [2 x i8] zeroinitializer
+@main.sliceSrcTaint.buf = internal global [2 x i8] c"cd"
+@main.sliceDstTaint.buf = internal global [2 x i8] zeroinitializer
 
 declare i64 @runtime.sliceCopy(ptr %dst, ptr %src, i64 %dstLen, i64 %srcLen, i64 %elemSize) unnamed_addr
 
@@ -16,6 +20,8 @@ declare void @runtime.printuint8(i8)
 
 declare void @runtime.printint16(i16)
 
+declare void @use(ptr)
+
 define void @runtime.initAll() unnamed_addr {
 entry:
   call void @main.init()
@@ -43,6 +49,15 @@ entry:
   %int16SliceDst.buf = load ptr, ptr @main.int16SliceDst
   %int16SliceDst.val = load i16, ptr %int16SliceDst.buf
   call void @runtime.printint16(i16 %int16SliceDst.val)
+
+  ; print(sliceDstUntaint[0])
+  %sliceDstUntaint.val = load i8, ptr getelementptr inbounds (i8, ptr @main.sliceDstUntaint.buf, i32 0)
+  call void @runtime.printuint8(i8 %sliceDstUntaint.val)
+
+  ; print(sliceDstTaint[0])
+  %sliceDstTaint.val = load i8, ptr getelementptr inbounds (i8, ptr @main.sliceDstTaint.buf, i32 0)
+  call void @runtime.printuint8(i8 %sliceDstTaint.val)
+
   ret void
 }
 
@@ -79,5 +94,13 @@ entry:
   %int16SliceSrc.buf = extractvalue { ptr, i64, i64 } %int16SliceSrc, 0
   %copy.n2 = call i64 @runtime.sliceCopy(ptr %int16SliceDst.buf, ptr %int16SliceSrc.buf, i64 %int16SliceSrc.len, i64 %int16SliceSrc.len, i64 2)
 
+  ; Copy slice that has a known value.
+  %copy.n3 = call i64 @runtime.sliceCopy(ptr @main.sliceDstUntaint.buf, ptr @main.sliceSrcUntaint.buf, i64 2, i64 2, i64 1)
+
+  ; Copy slice that might have been modified by the external @use call.
+  ; This is a fix for https://github.com/tinygo-org/tinygo/issues/3890.
+  call void @use(ptr @main.sliceSrcTaint.buf)
+  %copy.n4 = call i64 @runtime.sliceCopy(ptr @main.sliceDstTaint.buf, ptr @main.sliceSrcTaint.buf, i64 2, i64 2, i64 1)
+
   ret void
 }

interp/testdata/slice-copy.out.ll

@@ -1,12 +1,21 @@
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64--linux"
 
+@main.sliceSrcTaint.buf = internal global [2 x i8] c"cd"
+@main.sliceDstTaint.buf = internal global [2 x i8] zeroinitializer
+
+declare i64 @runtime.sliceCopy(ptr, ptr, i64, i64, i64) unnamed_addr
+
 declare void @runtime.printuint8(i8) local_unnamed_addr
 
 declare void @runtime.printint16(i16) local_unnamed_addr
 
+declare void @use(ptr) local_unnamed_addr
+
 define void @runtime.initAll() unnamed_addr {
 entry:
+  call void @use(ptr @main.sliceSrcTaint.buf)
+  %copy.n4 = call i64 @runtime.sliceCopy(ptr @main.sliceDstTaint.buf, ptr @main.sliceSrcTaint.buf, i64 2, i64 2, i64 1)
   ret void
 }
 
@@ -16,5 +25,8 @@ entry:
   call void @runtime.printuint8(i8 3)
   call void @runtime.printint16(i16 5)
   call void @runtime.printint16(i16 5)
+  call void @runtime.printuint8(i8 97)
+  %sliceDstTaint.val = load i8, ptr @main.sliceDstTaint.buf, align 1
+  call void @runtime.printuint8(i8 %sliceDstTaint.val)
   ret void
 }