Memory64Lowering: Handle -1 return value from memory.grow (#6733)

This edge case make the lowering a little more tricky.
WebAssembly · Jul 11, 2024 · 22c28bd · 22c28bd
1 parent 363edc7
commit 22c28bd
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Showing 2 changed files with 43 additions and 6 deletions.
diff --git a/src/passes/Memory64Lowering.cpp b/src/passes/Memory64Lowering.cpp
@@ -79,9 +79,32 @@ struct Memory64Lowering : public WalkerPass<PostWalker<Memory64Lowering>> {
  if (memory->is64()) {
  wrapAddress64(curr->delta, curr->memory);
  auto* size = static_cast<Expression*>(curr);
- extendAddress64(size, curr->memory);
+ // MemoryGrow returns -1 in case of failure. We cannot just use
+ // extend_32_u in this case so we handle it as follows:
+ //
+ // (if (result i64)
+ // (i32.eq (i32.const -1) (local.tee $tmp (memory.grow X)))
+ // (then
+ // (i64.const -1)
+ // )
+ // (else
+ // (i32.extend_32_u (local.get $tmp))
+ // )
+ // )
+ Builder builder(module);
+ auto tmp = builder.addVar(getFunction(), Type::i32);
+ Expression* isMinusOne =
+ builder.makeBinary(EqInt32,
+ builder.makeConst(int32_t(-1)),
+ builder.makeLocalTee(tmp, size, Type::i32));
+ auto* newSize = builder.makeLocalGet(tmp, Type::i32);
+ builder.makeUnary(UnaryOp::ExtendUInt32, newSize);
+ Expression* ifExp =
+ builder.makeIf(isMinusOne,
+ builder.makeConst(int64_t(-1)),
+ builder.makeUnary(UnaryOp::ExtendUInt32, newSize));
  curr->type = Type::i32;
- replaceCurrent(size);
+ replaceCurrent(ifExp);
  }
  }
 

diff --git a/test/lit/passes/memory64-lowering.wast b/test/lit/passes/memory64-lowering.wast
@@ -225,16 +225,30 @@
 
  ;; CHECK: (func $other
  ;; CHECK-NEXT: (local $0 i64)
+ ;; CHECK-NEXT: (local $1 i32)
  ;; CHECK-NEXT: (local.set $0
  ;; CHECK-NEXT: (i64.extend_i32_u
  ;; CHECK-NEXT: (memory.size)
  ;; CHECK-NEXT: )
  ;; CHECK-NEXT: )
  ;; CHECK-NEXT: (local.set $0
- ;; CHECK-NEXT: (i64.extend_i32_u
- ;; CHECK-NEXT: (memory.grow
- ;; CHECK-NEXT: (i32.wrap_i64
- ;; CHECK-NEXT: (i64.const 1)
+ ;; CHECK-NEXT: (if (result i64)
+ ;; CHECK-NEXT: (i32.eq
+ ;; CHECK-NEXT: (i32.const -1)
+ ;; CHECK-NEXT: (local.tee $1
+ ;; CHECK-NEXT: (memory.grow
+ ;; CHECK-NEXT: (i32.wrap_i64
+ ;; CHECK-NEXT: (i64.const 1)
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: (then
+ ;; CHECK-NEXT: (i64.const -1)
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: (else
+ ;; CHECK-NEXT: (i64.extend_i32_u
+ ;; CHECK-NEXT: (local.get $1)
  ;; CHECK-NEXT: )
  ;; CHECK-NEXT: )
  ;; CHECK-NEXT: )