diff --git a/interp/interp_test.go b/interp/interp_test.go
index 94682370ee..65f8b541bb 100644
--- a/interp/interp_test.go
+++ b/interp/interp_test.go
@@ -24,6 +24,7 @@ func TestInterp(t *testing.T) {
 		"slicedata",
 		"aggregate",
 		"fastrand",
+		"ptrtoint",
 	} {
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
diff --git a/interp/interpreter.go b/interp/interpreter.go
index 5d2c174182..3bf897909d 100644
--- a/interp/interpreter.go
+++ b/interp/interpreter.go
@@ -668,6 +668,29 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 			// while changing the LLVM type.
 			// Because interp doesn't preserve the type, these operations are
 			// identity operations.
+			if inst.opcode != llvm.BitCast {
+				bits := int(r.pointerSize * 8)
+				if inst.opcode == llvm.PtrToInt {
+					bits = inst.llvmInst.Type().IntTypeWidth()
+				}
+				if int(operands[0].len(r)*8) != bits {
+					// ptrtoint and inttoptr truncate or zero-extend when sizes differ.
+					// https://llvm.org/docs/LangRef.html#ptrtoint-to-instruction
+					_, isPtr := operands[0].(pointerValue)
+					if raw, ok := operands[0].(rawValue); ok && raw.hasPointer() {
+						isPtr = true
+					}
+					if isPtr || (bits != 8 && bits != 16 && bits != 32 && bits != 64) {
+						err := r.runAtRuntime(fn, inst, locals, &mem, indent)
+						if err != nil {
+							return nil, mem, err
+						}
+						continue
+					}
+					locals[inst.localIndex] = makeLiteralInt(operands[0].Uint(r), bits)
+					continue
+				}
+			}
 			if r.debug {
 				fmt.Fprintln(os.Stderr, indent+instructionNameMap[inst.opcode]+":", operands[0])
 			}
@@ -976,6 +999,10 @@ func (r *runner) runAtRuntime(fn *function, inst instruction, locals []value, me
 		}
 	case llvm.BitCast:
 		result = r.builder.CreateBitCast(operands[0], inst.llvmInst.Type(), inst.name)
+	case llvm.PtrToInt:
+		result = r.builder.CreatePtrToInt(operands[0], inst.llvmInst.Type(), inst.name)
+	case llvm.IntToPtr:
+		result = r.builder.CreateIntToPtr(operands[0], inst.llvmInst.Type(), inst.name)
 	case llvm.ExtractValue:
 		indices := inst.llvmInst.Indices()
 		// Note: the Go LLVM API doesn't support multiple indices, so simulate
diff --git a/interp/memory.go b/interp/memory.go
index c9c09898a1..a57b1fe20f 100644
--- a/interp/memory.go
+++ b/interp/memory.go
@@ -1004,10 +1004,11 @@ func (v rawValue) toLLVMValue(llvmType llvm.Type, mem *memoryView) (llvm.Value,
 	}
 }
 
-func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
+// set returns false if the constant can only be computed at runtime.
+func (v *rawValue) set(llvmValue llvm.Value, r *runner) bool {
 	if llvmValue.IsNull() {
 		// A zero value is common so check that first.
-		return
+		return true
 	}
 	if !llvmValue.IsAGlobalValue().IsNil() {
 		ptrSize := r.pointerSize
@@ -1020,11 +1021,25 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 		}
 	} else if !llvmValue.IsAConstantExpr().IsNil() {
 		switch llvmValue.Opcode() {
-		case llvm.IntToPtr, llvm.PtrToInt, llvm.BitCast:
-			// All these instructions effectively just reinterprets the bits
-			// (like a bitcast) while no bits change and keeping the same
-			// length, so just read its contents.
-			v.set(llvmValue.Operand(0), r)
+		case llvm.BitCast:
+			return v.set(llvmValue.Operand(0), r)
+		case llvm.IntToPtr, llvm.PtrToInt:
+			// These truncate or zero-extend when sizes differ.
+			// https://llvm.org/docs/LangRef.html#ptrtoint-to-instruction
+			operand := llvmValue.Operand(0)
+			src := newRawValue(uint32(r.targetData.TypeAllocSize(operand.Type())))
+			if !src.set(operand, r) {
+				return false
+			}
+			size := uint32(r.targetData.TypeAllocSize(llvmValue.Type()))
+			if src.len(r) != size && src.hasPointer() {
+				return false
+			}
+			if llvmValue.Type().TypeKind() == llvm.IntegerTypeKind && uint32(llvmValue.Type().IntTypeWidth()) != size*8 {
+				// Widths like i1 don't fill their bytes, so leave them for runtime.
+				return false
+			}
+			copy(v.buf[:size], src.buf)
 		case llvm.GetElementPtr:
 			ptr := llvmValue.Operand(0)
 			index := llvmValue.Operand(1)
@@ -1065,8 +1080,9 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 			size := r.targetData.TypeAllocSize(llvmValue.Operand(0).Type())
 			lhs := newRawValue(uint32(size))
 			rhs := newRawValue(uint32(size))
-			lhs.set(llvmValue.Operand(0), r)
-			rhs.set(llvmValue.Operand(1), r)
+			if !lhs.set(llvmValue.Operand(0), r) || !rhs.set(llvmValue.Operand(1), r) {
+				return false
+			}
 			if r.interpretICmp(lhs, rhs, llvmValue.IntPredicate()) {
 				v.buf[0] = 1 // result is true
 			} else {
@@ -1118,7 +1134,9 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 				field := rawValue{
 					buf: v.buf[offset:],
 				}
-				field.set(r.builder.CreateExtractValue(llvmValue, i, ""), r)
+				if !field.set(r.builder.CreateExtractValue(llvmValue, i, ""), r) {
+					return false
+				}
 			}
 		case llvm.ArrayTypeKind:
 			numElements := llvmType.ArrayLength()
@@ -1129,7 +1147,9 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 				field := rawValue{
 					buf: v.buf[offset:],
 				}
-				field.set(r.builder.CreateExtractValue(llvmValue, i, ""), r)
+				if !field.set(r.builder.CreateExtractValue(llvmValue, i, ""), r) {
+					return false
+				}
 			}
 		case llvm.DoubleTypeKind:
 			f, _ := llvmValue.DoubleValue()
@@ -1151,6 +1171,7 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 			panic("unknown constant")
 		}
 	}
+	return true
 }
 
 // hasPointer returns true if this raw value contains a pointer somewhere in the
@@ -1219,8 +1240,12 @@ func (r *runner) getValue(llvmValue llvm.Value) value {
 			if !llvmValue.IsAGlobalVariable().IsNil() {
 				obj.size = uint32(r.targetData.TypeAllocSize(llvmValue.GlobalValueType()))
 				if initializer := llvmValue.Initializer(); !initializer.IsNil() {
-					obj.buffer = r.getValue(initializer)
-					obj.constant = llvmValue.IsGlobalConstant()
+					// Treat the global as external if its initializer is only known at runtime.
+					buf := r.getValue(initializer)
+					if _, ok := buf.(localValue); !ok {
+						obj.buffer = buf
+						obj.constant = llvmValue.IsGlobalConstant()
+					}
 				}
 			} else if !llvmValue.IsAFunction().IsNil() {
 				// OK
@@ -1251,7 +1276,9 @@ func (r *runner) getValue(llvmValue llvm.Value) value {
 		}
 		size := r.targetData.TypeAllocSize(llvmValue.Type())
 		v := newRawValue(uint32(size))
-		v.set(llvmValue, r)
+		if !v.set(llvmValue, r) {
+			return localValue{llvmValue}
+		}
 		return v
 	} else if !llvmValue.IsAInstruction().IsNil() || !llvmValue.IsAArgument().IsNil() {
 		return localValue{llvmValue}
diff --git a/interp/testdata/ptrtoint.ll b/interp/testdata/ptrtoint.ll
new file mode 100644
index 0000000000..bb5ed96ade
--- /dev/null
+++ b/interp/testdata/ptrtoint.ll
@@ -0,0 +1,65 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+@main.v1 = global i32 0
+@main.v2 = global i64 0
+@main.v3 = global i8 0
+@main.global = global i8 0
+@main.v4 = global i8 0
+@main.v5 = global i8 0
+@main.v6 = global { i8, i8 } { i8 ptrtoint (ptr @main.global to i8), i8 7 }
+@main.v7 = global i8 0
+@main.v8 = global i1 0
+
+define void @runtime.initAll() unnamed_addr {
+entry:
+  call void @main.init()
+  ret void
+}
+
+define internal void @main.init() unnamed_addr {
+entry:
+  ; Narrow the receiver from a pointer, like an interface method thunk.
+  %v1 = call i32 @main.narrow.id.unpack(ptr inttoptr (i8 1 to ptr))
+  store i32 %v1, ptr @main.v1
+
+  ; Widen a narrow integer through a pointer.
+  %ptr = inttoptr i16 -1 to ptr
+  %v2 = ptrtoint ptr %ptr to i64
+  store i64 %v2, ptr @main.v2
+
+  ; A real pointer can't be truncated at compile time.
+  %v3 = ptrtoint ptr @main.global to i8
+  store i8 %v3, ptr @main.v3
+
+  ; The same conversions as constant expressions.
+  store i8 ptrtoint (ptr inttoptr (i64 258 to ptr) to i8), ptr @main.v4
+  store i8 ptrtoint (ptr @main.global to i8), ptr @main.v5
+
+  ; A global whose initializer can't be computed at compile time.
+  %v7 = load i8, ptr getelementptr inbounds (i8, ptr @main.v6, i64 1)
+  store i8 %v7, ptr @main.v7
+
+  ; A result narrower than its allocation size is left for runtime.
+  store i1 ptrtoint (ptr inttoptr (i64 2 to ptr) to i1), ptr @main.v8
+  ret void
+}
+
+define internal i32 @main.narrow.id.unpack(ptr %receiver) unnamed_addr {
+entry:
+  %unpack.int = ptrtoint ptr %receiver to i8
+  %ret = call i32 @main.narrow.id(i8 %unpack.int)
+  ret i32 %ret
+}
+
+define internal i32 @main.narrow.id(i8 %h) unnamed_addr {
+entry:
+  %cmp = icmp eq i8 %h, 1
+  br i1 %cmp, label %if.then, label %if.done
+
+if.then:
+  ret i32 10
+
+if.done:
+  ret i32 0
+}
diff --git a/interp/testdata/ptrtoint.out.ll b/interp/testdata/ptrtoint.out.ll
new file mode 100644
index 0000000000..26cf615db4
--- /dev/null
+++ b/interp/testdata/ptrtoint.out.ll
@@ -0,0 +1,22 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+@main.v1 = local_unnamed_addr global i32 10
+@main.v2 = local_unnamed_addr global i64 65535
+@main.v3 = local_unnamed_addr global i8 0
+@main.global = global i8 0
+@main.v4 = local_unnamed_addr global i8 2
+@main.v5 = local_unnamed_addr global i8 0
+@main.v6 = local_unnamed_addr global { i8, i8 } { i8 ptrtoint (ptr @main.global to i8), i8 7 }
+@main.v7 = local_unnamed_addr global i8 0
+@main.v8 = local_unnamed_addr global i1 false
+
+define void @runtime.initAll() unnamed_addr {
+entry:
+  store i8 ptrtoint (ptr @main.global to i8), ptr @main.v3, align 1
+  store i8 ptrtoint (ptr @main.global to i8), ptr @main.v5, align 1
+  %v7 = load i8, ptr getelementptr inbounds (i8, ptr @main.v6, i64 1), align 1
+  store i8 %v7, ptr @main.v7, align 1
+  store i1 ptrtoint (ptr inttoptr (i64 2 to ptr) to i1), ptr @main.v8, align 1
+  ret void
+}