[Qemu-devel] [PATCH 0/2] target-arm: Handle UNDEF cases for Neon load/stores

[Qemu-devel] [PATCH 0/2] target-arm: Handle UNDEF cases for Neon load/stores

[Peter Maydell]

These two simple patches make qemu correctly UNDEF where required in the
Neon load/store space. We also catch and UNDEF on an UNPREDICTABLE rather
than indexing off the end of the register file.

Tested in the usual way with random instruction sequences.

Peter Maydell (2):
  target-arm: Handle UNDEFs for Neon single element load/stores
  target-arm: Handle UNDEF cases for Neon VLD/VST multiple-structures

 target-arm/translate.c |   49 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 49 insertions(+), 0 deletions(-)

[Qemu-devel] [PATCH 1/2] target-arm: Handle UNDEFs for Neon single element load/stores

[Peter Maydell]

Handle the UNDEF and UNPREDICTABLE cases for Neon "single element to
one lane" VLD and "single element from one lane" VST.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/translate.c |   34 ++++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/target-arm/translate.c b/target-arm/translate.c
index 6190028..5820add 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -3975,6 +3975,7 @@ static int disas_neon_ls_insn(CPUState * env, DisasContext *s, uint32_t insn)
             stride = (1 << size) * nregs;
         } else {
             /* Single element.  */
+            int idx = (insn >> 4) & 0xf;
             pass = (insn >> 7) & 1;
             switch (size) {
             case 0:
@@ -3993,6 +3994,39 @@ static int disas_neon_ls_insn(CPUState * env, DisasContext *s, uint32_t insn)
                 abort();
             }
             nregs = ((insn >> 8) & 3) + 1;
+            /* Catch the UNDEF cases. This is unavoidably a bit messy. */
+            switch (nregs) {
+            case 1:
+                if (((idx & (1 << size)) != 0) ||
+                    (size == 2 && ((idx & 3) == 1 || (idx & 3) == 2))) {
+                    return 1;
+                }
+                break;
+            case 3:
+                if ((idx & 1) != 0) {
+                    return 1;
+                }
+                /* fall through */
+            case 2:
+                if (size == 2 && (idx & 2) != 0) {
+                    return 1;
+                }
+                break;
+            case 4:
+                if ((size == 2) && ((idx & 3) == 3)) {
+                    return 1;
+                }
+                break;
+            default:
+                abort();
+            }
+            if ((rd + stride * (nregs - 1)) > 31) {
+                /* Attempts to write off the end of the register file
+                 * are UNPREDICTABLE; we choose to UNDEF because otherwise
+                 * the neon_load_reg() would write off the end of the array.
+                 */
+                return 1;
+            }
             addr = tcg_temp_new_i32();
             load_reg_var(s, addr, rn);
             for (reg = 0; reg < nregs; reg++) {
-- 
1.7.1

[Qemu-devel] [PATCH 2/2] target-arm: Handle UNDEF cases for Neon VLD/VST multiple-structures

[Peter Maydell]

Correctly UNDEF for Neon VLD/VST "multiple structures" forms where the
align field is not valid.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/translate.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/target-arm/translate.c b/target-arm/translate.c
index 5820add..30ca7df 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -3830,6 +3830,21 @@ static int disas_neon_ls_insn(CPUState * env, DisasContext *s, uint32_t insn)
         size = (insn >> 6) & 3;
         if (op > 10)
             return 1;
+        /* Catch UNDEF cases for bad values of align field */
+        switch (op & 0xc) {
+        case 4:
+            if (((insn >> 5) & 1) == 1) {
+                return 1;
+            }
+            break;
+        case 8:
+            if (((insn >> 4) & 3) == 3) {
+                return 1;
+            }
+            break;
+        default:
+            break;
+        }
         nregs = neon_ls_element_type[op].nregs;
         interleave = neon_ls_element_type[op].interleave;
         spacing = neon_ls_element_type[op].spacing;
-- 
1.7.1

Re: [Qemu-devel] [PATCH 0/2] target-arm: Handle UNDEF cases for Neon load/stores

[Aurelien Jarno]

On Mon, Apr 18, 2011 at 07:07:10PM +0100, Peter Maydell wrote:
> These two simple patches make qemu correctly UNDEF where required in the
> Neon load/store space. We also catch and UNDEF on an UNPREDICTABLE rather
> than indexing off the end of the register file.
> 
> Tested in the usual way with random instruction sequences.
> 
> Peter Maydell (2):
>   target-arm: Handle UNDEFs for Neon single element load/stores
>   target-arm: Handle UNDEF cases for Neon VLD/VST multiple-structures
> 
>  target-arm/translate.c |   49 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 49 insertions(+), 0 deletions(-)
> 

Thanks, both applied.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net