64 lines
2.3 KiB
Go
64 lines
2.3 KiB
Go
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// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
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// SPDX-License-Identifier: BSD-3-Clause
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package lint
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import (
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"fmt"
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"strings"
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"sourcedock.dev/petrbalvin/gasm-sdk/ast"
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)
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// scanAddressing flags the two pseudo-register spellings the language
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// reference (docs/asm/OPERANDS.md) calls its sharpest edge: a numeric offset
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// against FP names no symbol, and a negative numeric offset against SP
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// addresses the hardware stack pointer rather than the virtual frame.
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func scanAddressing(t *ast.Text, cfg Config) []Diagnostic {
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var out []Diagnostic
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for _, s := range t.Body {
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in, ok := s.(*ast.Instr)
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if !ok {
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continue
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}
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for _, op := range in.Operands {
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if op.Kind != ast.OpAddr {
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continue
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}
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// FP is a pseudo-register, never a base register of a memory
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// operand; a Base of FP only arises from the numeric form
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// 0(FP), which the parser routes through memory parsing. The
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// toolchain rejects it with "cannot reference FP without a
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// symbol" and gasm with "unknown base register FP".
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if strings.EqualFold(op.Addr.Base, "FP") && !cfg.Disable[CodeUnnamedFPRef] {
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out = append(out, Diagnostic{
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Pos: op.Pos,
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Severity: Error,
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Code: CodeUnnamedFPRef,
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Message: "FP is referenced without a symbol; the assembler requires name+offset(FP)",
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})
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continue
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}
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// A numeric offset against (SP) addresses the hardware stack
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// pointer. Positive offsets are the deliberate runtime idiom
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// for reading caller frames, but a negative offset is exactly
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// the local-frame spelling with the name missing: x-8(SP) and
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// -8(SP) are one character apart and mean different registers.
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// Only the negative form is flagged, which keeps the rule
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// silent across GOROOT's 140-odd deliberate hardware-SP
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// references (all positive) while catching the mistyped local.
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if strings.EqualFold(op.Addr.Base, "SP") && op.Addr.Sym == nil &&
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op.Addr.HasOff && op.Addr.Offset < 0 && !cfg.Disable[CodeHardwareSP] {
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out = append(out, Diagnostic{
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Pos: op.Pos,
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Severity: Warning,
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Code: CodeHardwareSP,
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Message: fmt.Sprintf("%d(SP) addresses the hardware stack pointer, not the virtual frame; "+
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"a frame local is spelled x%d(SP)", op.Addr.Offset, op.Addr.Offset),
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})
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}
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}
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}
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return out
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}
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