diff options
Diffstat (limited to 'src/codegen')
| -rw-r--r-- | src/codegen/llvm.zig | 32 |
1 files changed, 27 insertions, 5 deletions
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig index 8cfa833cdd..cca83eca9b 100644 --- a/src/codegen/llvm.zig +++ b/src/codegen/llvm.zig @@ -3885,7 +3885,7 @@ pub const FuncGen = struct { fn genBody(self: *FuncGen, body: []const Air.Inst.Index) Error!void { const air_tags = self.air.instructions.items(.tag); - for (body) |inst| { + for (body) |inst, i| { const opt_value: ?*const llvm.Value = switch (air_tags[inst]) { // zig fmt: off .add => try self.airAdd(inst), @@ -3976,7 +3976,7 @@ pub const FuncGen = struct { .fptrunc => try self.airFptrunc(inst), .fpext => try self.airFpext(inst), .ptrtoint => try self.airPtrToInt(inst), - .load => try self.airLoad(inst), + .load => try self.airLoad(inst, body, i + 1), .loop => try self.airLoop(inst), .not => try self.airNot(inst), .ret => try self.airRet(inst), @@ -6982,11 +6982,33 @@ pub const FuncGen = struct { return null; } - fn airLoad(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value { + fn airLoad( + self: *FuncGen, + inst: Air.Inst.Index, + body: []const Air.Inst.Index, + body_i: usize, + ) !?*const llvm.Value { const ty_op = self.air.instructions.items(.data)[inst].ty_op; const ptr_ty = self.air.typeOf(ty_op.operand); - if (!ptr_ty.isVolatilePtr() and self.liveness.isUnused(inst)) - return null; + elide: { + const ptr_info = ptr_ty.ptrInfo().data; + if (ptr_info.@"volatile") break :elide; + if (self.liveness.isUnused(inst)) return null; + if (!isByRef(ptr_info.pointee_type)) break :elide; + + // It would be valid to fall back to the code below here that simply calls + // load(). However, as an optimization, we want to avoid unnecessary copies + // of isByRef=true types. Here, we scan forward in the current block, + // looking to see if this load dies before any side effects occur. + // In such case, we can safely return the operand without making a copy. + for (body[body_i..]) |body_inst| { + switch (self.liveness.categorizeOperand(self.air, body_inst, inst)) { + .none => continue, + .write, .noret, .complex => break :elide, + .tomb => return try self.resolveInst(ty_op.operand), + } + } else unreachable; + } const ptr = try self.resolveInst(ty_op.operand); return self.load(ptr, ptr_ty); } |