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[PATCH] target/arm: Fix sve pred_desc decoding

Richard Henderson posted 1 patch 3 years, 4 months ago
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Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20201230172522.33629-1-richard.henderson@linaro.org
Maintainers: Peter Maydell <peter.maydell@linaro.org>
There is a newer version of this series
target/arm/sve_helper.c | 46 ++++++++++++++++++++---------------------
1 file changed, 23 insertions(+), 23 deletions(-)
[PATCH] target/arm: Fix sve pred_desc decoding
Posted by Richard Henderson 3 years, 4 months ago 
There was an inconsistency between encoding, which uses
SIMD_DATA_SHIFT, and decoding which used SIMD_OPRSZ_BITS.
This happened to be ok, until e2e7168a214, which reduced
the size of SIMD_OPRSZ_BITS, which lead to truncating all
predicate vector lengths.

Cc: qemu-stable@nongnu.org
Buglink: https://bugs.launchpad.net/bugs/1908551
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---

Ouch.  The patch that exposed this, e2e7168a214, went in near
the start of the 5.2 devel period, and I never noticed.  I've
been doing most of my testing vs ArmIE of late, which due to
lack of a proper sve signal frame restricts RISU to sve128,
which worked fine with this truncation.  I need to spend some
time getting FVP working again...


r~

---
 target/arm/sve_helper.c | 46 ++++++++++++++++++++---------------------
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
index 5f037c3a8f..99e4b70d2f 100644
--- a/target/arm/sve_helper.c
+++ b/target/arm/sve_helper.c
@@ -914,7 +914,7 @@ uint32_t HELPER(sve_pfirst)(void *vd, void *vg, uint32_t words)
 
 uint32_t HELPER(sve_pnext)(void *vd, void *vg, uint32_t pred_desc)
 {
-    intptr_t words = extract32(pred_desc, 0, SIMD_OPRSZ_BITS);
+    intptr_t words = extract32(pred_desc, 0, SIMD_DATA_SHIFT);
     intptr_t esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
     uint32_t flags = PREDTEST_INIT;
     uint64_t *d = vd, *g = vg, esz_mask;
@@ -1867,7 +1867,7 @@ static uint64_t compress_bits(uint64_t x, int n)
 
 void HELPER(sve_zip_p)(void *vd, void *vn, void *vm, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     int esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
     intptr_t high = extract32(pred_desc, SIMD_DATA_SHIFT + 2, 1);
     uint64_t *d = vd;
@@ -1928,7 +1928,7 @@ void HELPER(sve_zip_p)(void *vd, void *vn, void *vm, uint32_t pred_desc)
 
 void HELPER(sve_uzp_p)(void *vd, void *vn, void *vm, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     int esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
     int odd = extract32(pred_desc, SIMD_DATA_SHIFT + 2, 1) << esz;
     uint64_t *d = vd, *n = vn, *m = vm;
@@ -1985,7 +1985,7 @@ void HELPER(sve_uzp_p)(void *vd, void *vn, void *vm, uint32_t pred_desc)
 
 void HELPER(sve_trn_p)(void *vd, void *vn, void *vm, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     uintptr_t esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
     bool odd = extract32(pred_desc, SIMD_DATA_SHIFT + 2, 1);
     uint64_t *d = vd, *n = vn, *m = vm;
@@ -2035,7 +2035,7 @@ static uint8_t reverse_bits_8(uint8_t x, int n)
 
 void HELPER(sve_rev_p)(void *vd, void *vn, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     int esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
     intptr_t i, oprsz_2 = oprsz / 2;
 
@@ -2065,7 +2065,7 @@ void HELPER(sve_rev_p)(void *vd, void *vn, uint32_t pred_desc)
 
 void HELPER(sve_punpk_p)(void *vd, void *vn, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     intptr_t high = extract32(pred_desc, SIMD_DATA_SHIFT + 2, 1);
     uint64_t *d = vd;
     intptr_t i;
@@ -2221,7 +2221,7 @@ void HELPER(sve_compact_d)(void *vd, void *vn, void *vg, uint32_t desc)
  */
 int32_t HELPER(sve_last_active_element)(void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     intptr_t esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
 
     return last_active_element(vg, DIV_ROUND_UP(oprsz, 8), esz);
@@ -2694,7 +2694,7 @@ static uint32_t do_zero(ARMPredicateReg *d, intptr_t oprsz)
 void HELPER(sve_brkpa)(void *vd, void *vn, void *vm, void *vg,
                        uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     if (last_active_pred(vn, vg, oprsz)) {
         compute_brk_z(vd, vm, vg, oprsz, true);
     } else {
@@ -2705,7 +2705,7 @@ void HELPER(sve_brkpa)(void *vd, void *vn, void *vm, void *vg,
 uint32_t HELPER(sve_brkpas)(void *vd, void *vn, void *vm, void *vg,
                             uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     if (last_active_pred(vn, vg, oprsz)) {
         return compute_brks_z(vd, vm, vg, oprsz, true);
     } else {
@@ -2716,7 +2716,7 @@ uint32_t HELPER(sve_brkpas)(void *vd, void *vn, void *vm, void *vg,
 void HELPER(sve_brkpb)(void *vd, void *vn, void *vm, void *vg,
                        uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     if (last_active_pred(vn, vg, oprsz)) {
         compute_brk_z(vd, vm, vg, oprsz, false);
     } else {
@@ -2727,7 +2727,7 @@ void HELPER(sve_brkpb)(void *vd, void *vn, void *vm, void *vg,
 uint32_t HELPER(sve_brkpbs)(void *vd, void *vn, void *vm, void *vg,
                             uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     if (last_active_pred(vn, vg, oprsz)) {
         return compute_brks_z(vd, vm, vg, oprsz, false);
     } else {
@@ -2737,55 +2737,55 @@ uint32_t HELPER(sve_brkpbs)(void *vd, void *vn, void *vm, void *vg,
 
 void HELPER(sve_brka_z)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     compute_brk_z(vd, vn, vg, oprsz, true);
 }
 
 uint32_t HELPER(sve_brkas_z)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     return compute_brks_z(vd, vn, vg, oprsz, true);
 }
 
 void HELPER(sve_brkb_z)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     compute_brk_z(vd, vn, vg, oprsz, false);
 }
 
 uint32_t HELPER(sve_brkbs_z)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     return compute_brks_z(vd, vn, vg, oprsz, false);
 }
 
 void HELPER(sve_brka_m)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     compute_brk_m(vd, vn, vg, oprsz, true);
 }
 
 uint32_t HELPER(sve_brkas_m)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     return compute_brks_m(vd, vn, vg, oprsz, true);
 }
 
 void HELPER(sve_brkb_m)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     compute_brk_m(vd, vn, vg, oprsz, false);
 }
 
 uint32_t HELPER(sve_brkbs_m)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     return compute_brks_m(vd, vn, vg, oprsz, false);
 }
 
 void HELPER(sve_brkn)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
 
     if (!last_active_pred(vn, vg, oprsz)) {
         do_zero(vd, oprsz);
@@ -2811,7 +2811,7 @@ static uint32_t predtest_ones(ARMPredicateReg *d, intptr_t oprsz,
 
 uint32_t HELPER(sve_brkns)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
 
     if (last_active_pred(vn, vg, oprsz)) {
         return predtest_ones(vd, oprsz, -1);
@@ -2822,7 +2822,7 @@ uint32_t HELPER(sve_brkns)(void *vd, void *vn, void *vg, uint32_t pred_desc)
 
 uint64_t HELPER(sve_cntp)(void *vn, void *vg, uint32_t pred_desc)
 {
-    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     intptr_t esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
     uint64_t *n = vn, *g = vg, sum = 0, mask = pred_esz_masks[esz];
     intptr_t i;
@@ -2836,7 +2836,7 @@ uint64_t HELPER(sve_cntp)(void *vn, void *vg, uint32_t pred_desc)
 
 uint32_t HELPER(sve_while)(void *vd, uint32_t count, uint32_t pred_desc)
 {
-    uintptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
+    uintptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
     intptr_t esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
     uint64_t esz_mask = pred_esz_masks[esz];
     ARMPredicateReg *d = vd;
-- 
2.25.1
Re: [PATCH] target/arm: Fix sve pred_desc decoding
Posted by Peter Maydell 3 years, 4 months ago 
On Wed, 30 Dec 2020 at 17:25, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> There was an inconsistency between encoding, which uses
> SIMD_DATA_SHIFT, and decoding which used SIMD_OPRSZ_BITS.
> This happened to be ok, until e2e7168a214, which reduced
> the size of SIMD_OPRSZ_BITS, which lead to truncating all
> predicate vector lengths.
>
> Cc: qemu-stable@nongnu.org
> Buglink: https://bugs.launchpad.net/bugs/1908551
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>
> Ouch.  The patch that exposed this, e2e7168a214, went in near
> the start of the 5.2 devel period, and I never noticed.  I've
> been doing most of my testing vs ArmIE of late, which due to
> lack of a proper sve signal frame restricts RISU to sve128,
> which worked fine with this truncation.  I need to spend some
> time getting FVP working again...
>
>
> r~
>
> ---
>  target/arm/sve_helper.c | 46 ++++++++++++++++++++---------------------
>  1 file changed, 23 insertions(+), 23 deletions(-)
>
> diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
> index 5f037c3a8f..99e4b70d2f 100644
> --- a/target/arm/sve_helper.c
> +++ b/target/arm/sve_helper.c
> @@ -914,7 +914,7 @@ uint32_t HELPER(sve_pfirst)(void *vd, void *vg, uint32_t words)
>
>  uint32_t HELPER(sve_pnext)(void *vd, void *vg, uint32_t pred_desc)
>  {
> -    intptr_t words = extract32(pred_desc, 0, SIMD_OPRSZ_BITS);
> +    intptr_t words = extract32(pred_desc, 0, SIMD_DATA_SHIFT);
>      intptr_t esz = extract32(pred_desc, SIMD_DATA_SHIFT, 2);
>      uint32_t flags = PREDTEST_INIT;
>      uint64_t *d = vd, *g = vg, esz_mask;
> @@ -1867,7 +1867,7 @@ static uint64_t compress_bits(uint64_t x, int n)
>
>  void HELPER(sve_zip_p)(void *vd, void *vn, void *vm, uint32_t pred_desc)
>  {
> -    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
> +    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;

Why do we not get oprsz by extracting SIMD_OPRSZ_BITS starting at
SIMD_OPRSZ_SHIFT ? (or even by calling simd_oprsz(), which
certainly looks like it ought to be a helper function for
extracting the oprsz...)

If the encoding constants in tcg-gvec-desc.h are right then
"SIMD_DATA_SHIFT bits starting at bit 0" is two fields glued
together (MAXSZ and OPRSZ).

thanks
-- PMM
Re: [PATCH] target/arm: Fix sve pred_desc decoding
Posted by Richard Henderson 3 years, 4 months ago 
On 1/7/21 8:02 AM, Peter Maydell wrote:
>>  void HELPER(sve_zip_p)(void *vd, void *vn, void *vm, uint32_t pred_desc)
>>  {
>> -    intptr_t oprsz = extract32(pred_desc, 0, SIMD_OPRSZ_BITS) + 2;
>> +    intptr_t oprsz = extract32(pred_desc, 0, SIMD_DATA_SHIFT) + 2;
> 
> Why do we not get oprsz by extracting SIMD_OPRSZ_BITS starting at
> SIMD_OPRSZ_SHIFT ? (or even by calling simd_oprsz(), which
> certainly looks like it ought to be a helper function for
> extracting the oprsz...)

The predicate operations are small -- minimum 2 bytes -- and cannot encode with
the real simd_oprsz (minumum 8, then multiples of 16).

This is shear abuse of the SIMD_* defines.  You're right that I shouldn't have
done this in the first place, and should probably rename everything having to
do with predicates.


r~

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