Remove reserved_reg functionality. (#424)

* Remove reserved_reg functionality.

This wasn't implemented, and if we need it in the future, it seems like
it would be better to extend the concept of global values to cover this.

* Use GlobalValue::reserved_value() for sentinal values.

cranelift/docs/langref.rst

@@ -689,16 +689,13 @@ trap when accessed.
 
     Declare a static heap in the preamble.
 
-    :arg Base: Global value holding the heap's base address or
+    :arg Base: Global value holding the heap's base address.
-            ``reserved_reg``.
     :arg MinBytes: Guaranteed minimum heap size in bytes. Accesses below this
             size will never trap.
     :arg BoundBytes: Fixed heap bound in bytes. This defines the amount of
             address space reserved for the heap, not including the guard pages.
     :arg GuardBytes: Size of the guard pages in bytes.
 
-The ``reserved_reg`` option is not yet implemented.
-
 Dynamic heaps
 ~~~~~~~~~~~~~
 
@@ -710,15 +707,12 @@ is resized. The bound of a dynamic heap is stored in a global value.
 
     Declare a dynamic heap in the preamble.
 
-    :arg Base: Global value holding the heap's base address or
+    :arg Base: Global value holding the heap's base address.
-            ``reserved_reg``.
     :arg MinBytes: Guaranteed minimum heap size in bytes. Accesses below this
             size will never trap.
     :arg BoundGV: Global value containing the current heap bound in bytes.
     :arg GuardBytes: Size of the guard pages in bytes.
 
-The ``reserved_reg`` option is not yet implemented.
-
 Heap examples
 ~~~~~~~~~~~~~
 

cranelift/filetests/parser/memory.clif

@@ -52,11 +52,11 @@ ebb0:
 
 ; Declare static heaps.
 function %sheap(i32, i64 vmctx) -> i64 {
-    heap1 = static reserved_reg, min 0x1_0000, bound 0x1_0000_0000, guard 0x8000_0000
+    heap1 = static gv5, min 0x1_0000, bound 0x1_0000_0000, guard 0x8000_0000
     heap2 = static gv5, guard 0x1000, bound 0x1_0000
     gv5 = vmctx+64
 
-    ; check: heap1 = static reserved_reg, min 0x0001_0000, bound 0x0001_0000_0000, guard 0x8000_0000
+    ; check: heap1 = static gv5, min 0x0001_0000, bound 0x0001_0000_0000, guard 0x8000_0000
     ; check: heap2 = static gv5, min 0, bound 0x0001_0000, guard 4096
 ebb0(v1: i32, v2: i64):
     v3 = heap_addr.i64 heap1, v1, 0
@@ -66,12 +66,12 @@ ebb0(v1: i32, v2: i64):
 
 ; Declare dynamic heaps.
 function %dheap(i32, i64 vmctx) -> i64 {
-    heap1 = dynamic reserved_reg, min 0x1_0000, bound gv6, guard 0x8000_0000
+    heap1 = dynamic gv5, min 0x1_0000, bound gv6, guard 0x8000_0000
     heap2 = dynamic gv5, bound gv6, guard 0x1000
     gv5 = vmctx+64
     gv6 = vmctx+72
 
-    ; check: heap1 = dynamic reserved_reg, min 0x0001_0000, bound gv6, guard 0x8000_0000
+    ; check: heap1 = dynamic gv5, min 0x0001_0000, bound gv6, guard 0x8000_0000
     ; check: heap2 = dynamic gv5, min 0, bound gv6, guard 4096
 ebb0(v1: i32, v2: i64):
     v3 = heap_addr.i64 heap2, v1, 0

lib/codegen/src/ir/heap.rs

@@ -7,8 +7,8 @@ use std::fmt;
 /// Information about a heap declaration.
 #[derive(Clone)]
 pub struct HeapData {
-    /// Method for determining the heap base address.
+    /// The address of the start of the heap's storage.
-    pub base: HeapBase,
+    pub base: GlobalValue,
 
     /// Guaranteed minimum heap size in bytes. Heap accesses before `min_size` don't need bounds
     /// checking.
@@ -21,18 +21,6 @@ pub struct HeapData {
     pub style: HeapStyle,
 }
 
-/// Method for determining the base address of a heap.
-#[derive(Clone)]
-pub enum HeapBase {
-    /// The heap base lives in a reserved register.
-    ///
-    /// This feature is not yet implemented.
-    ReservedReg,
-
-    /// The heap base is a global value.
-    GlobalValue(GlobalValue),
-}
-
 /// Style of heap including style-specific information.
 #[derive(Clone)]
 pub enum HeapStyle {
@@ -57,12 +45,7 @@ impl fmt::Display for HeapData {
             HeapStyle::Static { .. } => "static",
         })?;
 
-        match self.base {
+        write!(f, " {}, min {}", self.base, self.min_size)?;
-            HeapBase::ReservedReg => write!(f, " reserved_reg")?,
-            HeapBase::GlobalValue(gv) => write!(f, " {}", gv)?,
-        }
-
-        write!(f, ", min {}", self.min_size)?;
         match self.style {
             HeapStyle::Dynamic { bound_gv } => write!(f, ", bound {}", bound_gv)?,
             HeapStyle::Static { bound } => write!(f, ", bound {}", bound)?,

lib/codegen/src/ir/mod.rs

@@ -31,7 +31,7 @@ pub use ir::extfunc::{AbiParam, ArgumentExtension, ArgumentPurpose, ExtFuncData,
 pub use ir::extname::ExternalName;
 pub use ir::function::Function;
 pub use ir::globalvalue::GlobalValueData;
-pub use ir::heap::{HeapBase, HeapData, HeapStyle};
+pub use ir::heap::{HeapData, HeapStyle};
 pub use ir::instructions::{InstructionData, Opcode, ValueList, ValueListPool, VariableArgs};
 pub use ir::jumptable::JumpTableData;
 pub use ir::layout::Layout;

lib/codegen/src/legalizer/heap.rs

@@ -154,11 +154,7 @@ fn offset_addr(
     }
 
     // Add the heap base address base
-    match pos.func.heaps[heap].base {
+    let base_gv = pos.func.heaps[heap].base;
-        ir::HeapBase::ReservedReg => unimplemented!(),
-        ir::HeapBase::GlobalValue(base_gv) => {
     let base = pos.ins().global_value(addr_ty, base_gv);
     pos.func.dfg.replace(inst).iadd(base, offset);
-        }
-    }
 }

lib/reader/src/parser.rs

@@ -8,9 +8,8 @@ use cranelift_codegen::ir::instructions::{InstructionData, InstructionFormat, Va
 use cranelift_codegen::ir::types::VOID;
 use cranelift_codegen::ir::{
     AbiParam, ArgumentExtension, ArgumentLoc, Ebb, ExtFuncData, ExternalName, FuncRef, Function,
-    GlobalValue, GlobalValueData, Heap, HeapBase, HeapData, HeapStyle, JumpTable, JumpTableData,
+    GlobalValue, GlobalValueData, Heap, HeapData, HeapStyle, JumpTable, JumpTableData, MemFlags,
-    MemFlags, Opcode, SigRef, Signature, StackSlot, StackSlotData, StackSlotKind, Type, Value,
+    Opcode, SigRef, Signature, StackSlot, StackSlotData, StackSlotKind, Type, Value, ValueLoc,
-    ValueLoc,
 };
 use cranelift_codegen::isa::{self, Encoding, RegUnit, TargetIsa};
 use cranelift_codegen::packed_option::ReservedValue;
@@ -168,7 +167,7 @@ impl<'a> Context<'a> {
         self.map.def_heap(heap, loc)?;
         while self.function.heaps.next_key().index() <= heap.index() {
             self.function.create_heap(HeapData {
-                base: HeapBase::ReservedReg,
+                base: GlobalValue::reserved_value(),
                 min_size: Imm64::new(0),
                 guard_size: Imm64::new(0),
                 style: HeapStyle::Static {
@@ -1123,8 +1122,7 @@ impl<'a> Parser<'a> {
     // heap-decl ::= * Heap(heap) "=" heap-desc
     // heap-desc ::= heap-style heap-base { "," heap-attr }
     // heap-style ::= "static" | "dynamic"
-    // heap-base ::= "reserved_reg"
+    // heap-base ::= GlobalValue(base)
-    //             | GlobalValue(base)
     // heap-attr ::= "min" Imm64(bytes)
     //             | "max" Imm64(bytes)
     //             | "guard" Imm64(bytes)
@@ -1136,17 +1134,12 @@ impl<'a> Parser<'a> {
         let style_name = self.match_any_identifier("expected 'static' or 'dynamic'")?;
 
         // heap-desc ::= heap-style * heap-base { "," heap-attr }
-        // heap-base ::= * "reserved_reg"
+        // heap-base ::= * GlobalValue(base)
-        //             | * GlobalValue(base)
         let base = match self.token() {
-            Some(Token::Identifier("reserved_reg")) => HeapBase::ReservedReg,
+            Some(Token::GlobalValue(base_num)) => match GlobalValue::with_number(base_num) {
-            Some(Token::GlobalValue(base_num)) => {
-                let base_gv = match GlobalValue::with_number(base_num) {
                 Some(gv) => gv,
                 None => return err!(self.loc, "invalid global value number for heap base"),
-                };
+            },
-                HeapBase::GlobalValue(base_gv)
-            }
             _ => return err!(self.loc, "expected heap base"),
         };
         self.consume();

lib/wasm/src/environ/dummy.rs

@@ -172,7 +172,7 @@ impl<'dummy_environment> FuncEnvironment for DummyFuncEnvironment<'dummy_environ
         let gv = func.create_global_value(ir::GlobalValueData::VMContext { offset: 0.into() });
 
         func.create_heap(ir::HeapData {
-            base: ir::HeapBase::GlobalValue(gv),
+            base: gv,
             min_size: 0.into(),
             guard_size: 0x8000_0000.into(),
             style: ir::HeapStyle::Static {