For WHILE, we have the count of enabled predicates, so we don't
need to search to compute the PredTest result.  Reuse the logic
that will shortly be required for counted predicates.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/arm/tcg/sve_helper.c | 47 ++++++++++++++++++++++---------------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff --git a/target/arm/tcg/sve_helper.c b/target/arm/tcg/sve_helper.c
index 0e59ad2262..8fb9d0241d 100644
--- a/target/arm/tcg/sve_helper.c
+++ b/target/arm/tcg/sve_helper.c
@@ -4102,20 +4102,35 @@ uint64_t HELPER(sve_cntp)(void *vn, void *vg, uint32_t pred_desc)
     return sum;
 }
 
+/* C.f. Arm pseudocode PredCountTest */
+static uint32_t pred_count_test(uint32_t elements, uint32_t count, bool invert)
+{
+    uint32_t flags;
+
+    if (count == 0) {
+        flags = 1;                              /* !N, Z, C */
+    } else if (!invert) {
+        flags = (1u << 31) | 2;                 /* N, !Z */
+        flags |= count != elements;             /* C */
+    } else {
+        flags = 2;                              /* !Z, !C */
+        flags |= (count == elements) << 31;     /* N */
+    }
+    return flags;
+}
+
 uint32_t HELPER(sve_whilel)(void *vd, uint32_t count, uint32_t pred_desc)
 {
     intptr_t oprsz = FIELD_EX32(pred_desc, PREDDESC, OPRSZ);
     intptr_t esz = FIELD_EX32(pred_desc, PREDDESC, ESZ);
     uint64_t esz_mask = pred_esz_masks[esz];
     ARMPredicateReg *d = vd;
-    uint32_t flags;
-    intptr_t i;
+    intptr_t i, oprbits = oprsz * 8;
+
+    tcg_debug_assert(count <= oprbits);
 
     /* Begin with a zero predicate register.  */
-    flags = do_zero(d, oprsz);
-    if (count == 0) {
-        return flags;
-    }
+    do_zero(d, oprsz);
 
     /* Set all of the requested bits.  */
     for (i = 0; i < count / 64; ++i) {
@@ -4125,7 +4140,7 @@ uint32_t HELPER(sve_whilel)(void *vd, uint32_t count, uint32_t pred_desc)
         d->p[i] = MAKE_64BIT_MASK(0, count & 63) & esz_mask;
     }
 
-    return predtest_ones(d, oprsz, esz_mask);
+    return pred_count_test(oprbits, count, false);
 }
 
 uint32_t HELPER(sve_whileg)(void *vd, uint32_t count, uint32_t pred_desc)
@@ -4134,16 +4149,15 @@ uint32_t HELPER(sve_whileg)(void *vd, uint32_t count, uint32_t pred_desc)
     intptr_t esz = FIELD_EX32(pred_desc, PREDDESC, ESZ);
     uint64_t esz_mask = pred_esz_masks[esz];
     ARMPredicateReg *d = vd;
-    intptr_t i, invcount, oprbits;
+    intptr_t i, invcount, oprbits = oprsz * 8;
     uint64_t bits;
 
-    if (count == 0) {
-        return do_zero(d, oprsz);
-    }
-
-    oprbits = oprsz * 8;
     tcg_debug_assert(count <= oprbits);
 
+    /* Begin with a zero predicate register.  */
+    do_zero(d, oprsz);
+
+    /* Set all of the requested bits.  */
     bits = esz_mask;
     if (oprbits & 63) {
         bits &= MAKE_64BIT_MASK(0, oprbits & 63);
@@ -4154,14 +4168,9 @@ uint32_t HELPER(sve_whileg)(void *vd, uint32_t count, uint32_t pred_desc)
         d->p[i] = bits;
         bits = esz_mask;
     }
-
     d->p[i] = bits & MAKE_64BIT_MASK(invcount & 63, 64);
 
-    while (--i >= 0) {
-        d->p[i] = 0;
-    }
-
-    return predtest_ones(d, oprsz, esz_mask);
+    return pred_count_test(oprbits, count, true);
 }
 
 /* Recursive reduction on a function;
-- 
2.43.0

On 7/2/25 06:33, Richard Henderson wrote:
> For WHILE, we have the count of enabled predicates, so we don't
> need to search to compute the PredTest result.  Reuse the logic
> that will shortly be required for counted predicates.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   target/arm/tcg/sve_helper.c | 47 ++++++++++++++++++++++---------------
>   1 file changed, 28 insertions(+), 19 deletions(-)

Hmm.

> @@ -4134,16 +4149,15 @@ uint32_t HELPER(sve_whileg)(void *vd, uint32_t count, uint32_t pred_desc)
>       intptr_t esz = FIELD_EX32(pred_desc, PREDDESC, ESZ);
>       uint64_t esz_mask = pred_esz_masks[esz];
>       ARMPredicateReg *d = vd;
> -    intptr_t i, invcount, oprbits;
> +    intptr_t i, invcount, oprbits = oprsz * 8;
>       uint64_t bits;
>   
> -    if (count == 0) {
> -        return do_zero(d, oprsz);
> -    }

It's possible this breaks sve_whileg until it's fixed by patch 63.


r~