[PATCH v5] gdb/hppa-tdep.c: Fix logical working flow issues and check additional store instructions

Chen Gang
2014-12-18T21:02:15Z

Original working flow has several issues:

- typo issue: "(inst >> 26) == 0x1f && ..." for checking 'stw(m)'.

- compiler warning: "(inst >> 6) & 0xf) == 0x9" for checking 'sth'.

- "(inst >> 6) == 0xa" needs to be "((inst >> 6) & 0xf) == 0xa".

And also need check additional store instructions:

- For absolute memory: 'stby', 'stdby'.

- For unaligned: 'stwa', 'stda'.

The original code also can be improved:

- Remove redundant double check "(inst >> 26) == 0x1b" for 'stwm'.

- Use 2 'switch' statements instead of all 'if' statements.

2014-12-19 Chen Gang <gang.chen.5i5j@gmail.com>

* hppa-tdep.c (inst_saves_gr): Fix logical working flow issues
and check additional store instructions.
---
gdb/hppa-tdep.c | 121 ++++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 95 insertions(+), 26 deletions(-)

diff --git a/gdb/hppa-tdep.c b/gdb/hppa-tdep.c
index 627f31a..4cae7b2 100644
--- a/gdb/hppa-tdep.c
+++ b/gdb/hppa-tdep.c
@@ -1376,37 +1376,106 @@ is_branch (unsigned long inst)
}

/* Return the register number for a GR which is saved by INST or
- zero it INST does not save a GR. */
+ zero if INST does not save a GR.

-static int
-inst_saves_gr (unsigned long inst)
-{
- /* Does it look like a stw? */
- if ((inst >> 26) == 0x1a || (inst >> 26) == 0x1b
- || (inst >> 26) == 0x1f
- || ((inst >> 26) == 0x1f
- && ((inst >> 6) == 0xa)))
- return hppa_extract_5R_store (inst);
+ Referenced from:

- /* Does it look like a std? */
- if ((inst >> 26) == 0x1c
- || ((inst >> 26) == 0x03
- && ((inst >> 6) & 0xf) == 0xb))
- return hppa_extract_5R_store (inst);
+ parisc 1.1:
+ https://parisc.wiki.kernel.org/images-parisc/6/68/Pa11_acd.pdf

- /* Does it look like a stwm? GCC & HPC may use this in prologues. */
- if ((inst >> 26) == 0x1b)
- return hppa_extract_5R_store (inst);
+ parisc 2.0:
+ https://parisc.wiki.kernel.org/images-parisc/7/73/Parisc2.0.pdf

- /* Does it look like sth or stb? HPC versions 9.0 and later use these
- too. */
- if ((inst >> 26) == 0x19 || (inst >> 26) == 0x18
- || ((inst >> 26) == 0x3
- && (((inst >> 6) & 0xf) == 0x8
- || (inst >> 6) & 0xf) == 0x9))
- return hppa_extract_5R_store (inst);
+ According to Table 6-5 of Chapter 6 (Memory Reference Instructions)
+ on page 106 in parisc 2.0, all instructions for storing values from
+ the general registers are:

- return 0;
+ Store: stb, sth, stw, std (according to Chapter 7, they
+ are only in both "inst >> 26" and "inst >> 6".
+ Store Absolute: stwa, stda (according to Chapter 7, they are only
+ in "inst >> 6".
+ Store Bytes: stby, stdby (according to Chapter 7, they are
+ only in "inst >> 6").
+
+ For (inst >> 26), according to Chapter 7:
+
+ The effective memory reference address is formed by the addition
+ of an immediate displacement to a base value.
+
+ - stb: 0x18, store a byte from a general register.
+
+ - sth: 0x19, store a halfword from a general register.
+
+ - stw: 0x1a, store a word from a general register.
+
+ - stwm: 0x1b, store a word from a general register and perform base
+ register modification (2.0 will still treate it as stw).
+
+ - std: 0x1c, store a doubleword from a general register (2.0 only).
+
+ - stw: 0x1f, store a word from a general register (2.0 only).
+
+ For (inst >> 6) when ((inst >> 26) == 0x03), according to Chapter 7:
+
+ The effective memory reference address is formed by the addition
+ of an index value to a base value specified in the instruction.
+
+ - stb: 0x08, store a byte from a general register (1.1 calls stbs).
+
+ - sth: 0x09, store a halfword from a general register (1.1 calls
+ sths).
+
+ - stw: 0x0a, store a word from a general register (1.1 calls stws).
+
+ - std: 0x0b: store a doubleword from a general register (2.0 only)
+
+ Implement fast byte moves (stores) to unaligned word or doubleword
+ destination.
+
+ - stby: 0x0c, for unaligned word (1.1 calls stbys).
+
+ - stdby: 0x0d for unaligned doubleword (2.0 only).
+
+ Store a word or doubleword using an absolute memory address formed
+ using short or long displacement or indexed
+
+ - stwa: 0x0e, store a word from a general register to an absolute
+ address (1.0 calls stwas).
+
+ - stda: 0x0f, store a doubleword from a general register to an
+ absolute address (2.0 only). */
+
+static int
+inst_saves_gr (unsigned long inst)
+{
+ switch ((inst >> 26) & 0x0f)
+ {
+ case 0x03:
+ switch ((inst >> 6) & 0x0f)
+ {
+ case 0x08:
+ case 0x09:
+ case 0x0a:
+ case 0x0b:
+ case 0x0c:
+ case 0x0d:
+ case 0x0e:
+ case 0x0f:
+ return hppa_extract_5R_store (inst);
+ default:
+ return 0;
+ }
+ case 0x18:
+ case 0x19:
+ case 0x1a:
+ case 0x1b:
+ case 0x1c:
+ /* no 0x1d or 0x1e -- according to parisc 2.0 document */
+ case 0x1f:
+ return hppa_extract_5R_store (inst);
+ default:
+ return 0;
+ }
}

/* Return the register number for a FR which is saved by INST or
--
1.9.3