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Sema: reimplement runtime switch

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Now supports multiple items pointing to the same body. This is a common
pattern even when using a jump table, with multiple cases pointing to
the same block of code.

In the case of a range specified, the items are moved to branches in the
else body. A future improvement may make it possible to have jump table
items as well as ranges pointing to the same block of code.
This commit is contained in:
Andrew Kelley
2021-07-19 17:35:14 -07:00
parent caa0de545e
commit ea902ffe8f
4 changed files with 217 additions and 165 deletions
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67
src/codegen/wasm.zig
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@@ -1282,44 +1282,49 @@ pub const Context = struct {
// result type is always 'noreturn'
const blocktype = wasm.block_empty;
const signedness: std.builtin.Signedness = blk: {
// by default we tell the operand type is unsigned (i.e. bools and enum values)
if (target_ty.zigTypeTag() != .Int) break :blk .unsigned;
_ = valtype;
_ = blocktype;
_ = target;
_ = else_body;
return self.fail("TODO implement wasm codegen for switch", .{});
//const signedness: std.builtin.Signedness = blk: {
// // by default we tell the operand type is unsigned (i.e. bools and enum values)
// if (target_ty.zigTypeTag() != .Int) break :blk .unsigned;
// incase of an actual integer, we emit the correct signedness
break :blk target_ty.intInfo(self.target).signedness;
};
for (cases) |case_idx| {
const case = self.air.extraData(Air.SwitchBr.Case, case_idx);
const case_body = self.air.extra[case.end..][0..case.data.body_len];
// // incase of an actual integer, we emit the correct signedness
// break :blk target_ty.intInfo(self.target).signedness;
//};
//for (cases) |case_idx| {
// const case = self.air.extraData(Air.SwitchBr.Case, case_idx);
// const case_body = self.air.extra[case.end..][0..case.data.body_len];
// create a block for each case, when the condition does not match we break out of it
try self.startBlock(.block, blocktype, null);
try self.emitWValue(target);
// // create a block for each case, when the condition does not match we break out of it
// try self.startBlock(.block, blocktype, null);
// try self.emitWValue(target);
const val = self.air.value(case.data.item).?;
try self.emitConstant(val, target_ty);
const opcode = buildOpcode(.{
.valtype1 = valtype,
.op = .ne, // not equal because we jump out the block if it does not match the condition
.signedness = signedness,
});
try self.code.append(wasm.opcode(opcode));
try self.code.append(wasm.opcode(.br_if));
try leb.writeULEB128(self.code.writer(), @as(u32, 0));
// const val = self.air.value(case.data.item).?;
// try self.emitConstant(val, target_ty);
// const opcode = buildOpcode(.{
// .valtype1 = valtype,
// .op = .ne, // not equal because we jump out the block if it does not match the condition
// .signedness = signedness,
// });
// try self.code.append(wasm.opcode(opcode));
// try self.code.append(wasm.opcode(.br_if));
// try leb.writeULEB128(self.code.writer(), @as(u32, 0));
// emit our block code
try self.genBody(case_body);
// // emit our block code
// try self.genBody(case_body);
// end the block we created earlier
try self.endBlock();
}
// // end the block we created earlier
// try self.endBlock();
//}
// finally, emit the else case if it exists. Here we will not have to
// check for a condition, so also no need to emit a block.
try self.genBody(else_body);
//// finally, emit the else case if it exists. Here we will not have to
//// check for a condition, so also no need to emit a block.
//try self.genBody(else_body);
return .none;
//return .none;
}
fn airIsErr(self: *Context, inst: Air.Inst.Index, opcode: wasm.Opcode) InnerError!WValue {