Add heap_addr custom legalization.

The expansion of a heap_addr instruction depends on the type of heap and
its configuration, so this is handled by custom code.

Add a couple examples of heap access code to the language reference
manual.

lib/cretonne/meta/base/legalize.py

@@ -46,6 +46,7 @@ expand = XFormGroup('expand', """
 
 # Custom expansions for memory objects.
 expand.custom_legalize(insts.global_addr, 'expand_global_addr')
+expand.custom_legalize(insts.heap_addr, 'expand_heap_addr')
 
 x = Var('x')
 y = Var('y')

lib/cretonne/src/legalizer/heap.rs

@@ -0,0 +1,144 @@
+//! Legalization of heaps.
+//!
+//! This module exports the `expand_heap_addr` function which transforms a `heap_addr`
+//! instruction into code that depends on the kind of heap referenced.
+
+use cursor::{Cursor, FuncCursor};
+use flowgraph::ControlFlowGraph;
+use ir::{self, InstBuilder, MemFlags};
+use ir::condcodes::IntCC;
+
+/// Expand a `heap_addr` instruction according to the definition of the heap.
+pub fn expand_heap_addr(inst: ir::Inst, func: &mut ir::Function, _cfg: &mut ControlFlowGraph) {
+    // Unpack the instruction.
+    let (heap, offset, size) = match &func.dfg[inst] {
+        &ir::InstructionData::HeapAddr {
+            opcode,
+            heap,
+            arg,
+            imm,
+        } => {
+            assert_eq!(opcode, ir::Opcode::HeapAddr);
+            (heap, arg, imm.into())
+        }
+        _ => panic!("Wanted heap_addr: {}", func.dfg.display_inst(inst, None)),
+    };
+
+    match func.heaps[heap].style {
+        ir::HeapStyle::Dynamic { bound_gv } => {
+            dynamic_addr(inst, heap, offset, size, bound_gv, func)
+        }
+        ir::HeapStyle::Static { bound } => {
+            static_addr(inst, heap, offset, size, bound.into(), func)
+        }
+    }
+}
+
+/// Expand a `heap_addr` for a dynamic heap.
+fn dynamic_addr(inst: ir::Inst,
+                heap: ir::Heap,
+                offset: ir::Value,
+                size: u32,
+                bound_gv: ir::GlobalVar,
+                func: &mut ir::Function) {
+    let size = size as i64;
+    let offset_ty = func.dfg.value_type(offset);
+    let addr_ty = func.dfg.value_type(func.dfg.first_result(inst));
+    let min_size = func.heaps[heap].min_size.into();
+    let mut pos = FuncCursor::new(func).at_inst(inst);
+
+    // Start with the bounds check. Trap if `offset + size > bound`.
+    let bound_addr = pos.ins().global_addr(addr_ty, bound_gv);
+    let bound = pos.ins().load(offset_ty, MemFlags::new(), bound_addr, 0);
+
+    let oob;
+    if size == 1 {
+        // `offset > bound - 1` is the same as `offset >= bound`.
+        oob = pos.ins()
+            .icmp(IntCC::UnsignedGreaterThanOrEqual, offset, bound);
+    } else if size <= min_size {
+        // We know that bound >= min_size, so here we can compare `offset > bound - size` without
+        // wrapping.
+        let adj_bound = pos.ins().iadd_imm(bound, -size);
+        oob = pos.ins()
+            .icmp(IntCC::UnsignedGreaterThan, offset, adj_bound);
+    } else {
+        // We need an overflow check for the adjusted offset.
+        let size_val = pos.ins().iconst(offset_ty, size);
+        let (adj_offset, overflow) = pos.ins().iadd_cout(offset, size_val);
+        pos.ins().trapnz(overflow);
+        oob = pos.ins()
+            .icmp(IntCC::UnsignedGreaterThan, adj_offset, bound);
+    }
+    pos.ins().trapnz(oob);
+
+    offset_addr(inst, heap, addr_ty, offset, offset_ty, pos.func);
+}
+
+/// Expand a `heap_addr` for a static heap.
+fn static_addr(inst: ir::Inst,
+               heap: ir::Heap,
+               offset: ir::Value,
+               size: u32,
+               bound: i64,
+               func: &mut ir::Function) {
+    let size = size as i64;
+    let offset_ty = func.dfg.value_type(offset);
+    let addr_ty = func.dfg.value_type(func.dfg.first_result(inst));
+    let mut pos = FuncCursor::new(func).at_inst(inst);
+
+    // Start with the bounds check. Trap if `offset + size > bound`.
+    if size > bound {
+        // This will simply always trap since `offset >= 0`.
+        pos.ins().trap();
+        pos.func.dfg.replace(inst).iconst(addr_ty, 0);
+        return;
+    }
+
+    // Check `offset > limit` which is now known non-negative.
+    let limit = bound - size;
+
+    // We may be able to omit the check entirely for 32-bit offsets if the heap bound is 4 GB or
+    // more.
+    if offset_ty != ir::types::I32 || limit < 0xffff_ffff {
+        let oob = if limit & 1 == 1 {
+            // Prefer testing `offset >= limit - 1` when limit is odd because an even number is
+            // likely to be a convenient constant on ARM and other RISC architectures.
+            pos.ins()
+                .icmp_imm(IntCC::UnsignedGreaterThanOrEqual, offset, limit - 1)
+        } else {
+            pos.ins()
+                .icmp_imm(IntCC::UnsignedGreaterThan, offset, limit)
+        };
+        pos.ins().trapnz(oob);
+    }
+
+    offset_addr(inst, heap, addr_ty, offset, offset_ty, pos.func);
+}
+
+/// Emit code for the base address computation of a `heap_addr` instruction.
+///
+///
+fn offset_addr(inst: ir::Inst,
+               heap: ir::Heap,
+               addr_ty: ir::Type,
+               mut offset: ir::Value,
+               offset_ty: ir::Type,
+               func: &mut ir::Function) {
+    let mut pos = FuncCursor::new(func).at_inst(inst);
+
+    // Convert `offset` to `addr_ty`.
+    if offset_ty != addr_ty {
+        offset = pos.ins().uextend(addr_ty, offset);
+    }
+
+    // Add the heap base address base
+    match pos.func.heaps[heap].base {
+        ir::HeapBase::ReservedReg => unimplemented!(),
+        ir::HeapBase::GlobalVar(base_gv) => {
+            let base_addr = pos.ins().global_addr(addr_ty, base_gv);
+            let base = pos.ins().load(addr_ty, MemFlags::new(), base_addr, 0);
+            pos.func.dfg.replace(inst).iadd(base, offset);
+        }
+    }
+}

lib/cretonne/src/legalizer/mod.rs

@@ -22,9 +22,11 @@ use bitset::BitSet;
 
 mod boundary;
 mod globalvar;
+mod heap;
 mod split;
 
 use self::globalvar::expand_global_addr;
+use self::heap::expand_heap_addr;
 
 /// Legalize `func` for `isa`.
 ///