diff options
Diffstat (limited to 'kvx/Asmvliw.v')
| -rw-r--r-- | kvx/Asmvliw.v | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/kvx/Asmvliw.v b/kvx/Asmvliw.v index aa2e0885..45b230e6 100644 --- a/kvx/Asmvliw.v +++ b/kvx/Asmvliw.v @@ -313,7 +313,11 @@ Inductive cf_instruction : Type := . (** *** Loads *) -Definition concrete_default_notrap_load_value (chunk : memory_chunk) := + +(* What follows was the original spec, but is subtly incorrect. + Our definition of the assembly-level memory model is already an abstraction of the real world. + In particular, we consider that a load is incorrect when it points outside of CompCert's visible memory, whereas this memory could be correct at the assembly level. + This means that CompCert would believe an incorrect load would yield 0 whereas it would yield another value. match chunk with | Mint8signed | Mint8unsigned | Mint16signed | Mint16unsigned | Mint32 => Vint Int.zero @@ -321,7 +325,7 @@ Definition concrete_default_notrap_load_value (chunk : memory_chunk) := | Many32 | Many64 => Vundef | Mfloat32 => Vsingle Float32.zero | Mfloat64 => Vfloat Float.zero - end. + end. *) Inductive load_name : Type := | Plb (**r load byte *) @@ -1169,16 +1173,16 @@ Definition eval_offset (ofs: offset) : res ptrofs := OK ofs. (** *** load/store instructions *) -Definition parexec_incorrect_load trap chunk d rsw mw := +Definition parexec_incorrect_load trap d rsw mw := match trap with | TRAP => Stuck - | NOTRAP => Next (rsw#d <- (concrete_default_notrap_load_value chunk)) mw + | NOTRAP => Next (rsw#d <- Vundef) mw end. Definition parexec_load_offset (trap: trapping_mode) (chunk: memory_chunk) (rsr rsw: regset) (mr mw: mem) (d a: ireg) (ofs: offset) := match (eval_offset ofs) with | OK ptr => match Mem.loadv chunk mr (Val.offset_ptr (rsr a) ptr) with - | None => parexec_incorrect_load trap chunk d rsw mw + | None => parexec_incorrect_load trap d rsw mw | Some v => Next (rsw#d <- v) mw end | _ => Stuck @@ -1225,13 +1229,13 @@ Definition parexec_load_o_offset (rsr rsw: regset) (mr mw: mem) (d : gpreg_o) (a Definition parexec_load_reg (trap: trapping_mode) (chunk: memory_chunk) (rsr rsw: regset) (mr mw: mem) (d a ro: ireg) := match Mem.loadv chunk mr (Val.addl (rsr a) (rsr ro)) with - | None => parexec_incorrect_load trap chunk d rsw mw + | None => parexec_incorrect_load trap d rsw mw | Some v => Next (rsw#d <- v) mw end. Definition parexec_load_regxs (trap: trapping_mode) (chunk: memory_chunk) (rsr rsw: regset) (mr mw: mem) (d a ro: ireg) := match Mem.loadv chunk mr (Val.addl (rsr a) (Val.shll (rsr ro) (scale_of_chunk chunk))) with - | None => parexec_incorrect_load trap chunk d rsw mw + | None => parexec_incorrect_load trap d rsw mw | Some v => Next (rsw#d <- v) mw end. |