[PATCH v5 22/31] target/arm: Enforce alignment for VLDn (all lanes)

From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>, qemu-arm@nongnu.org
Subject: [PATCH v5 22/31] target/arm: Enforce alignment for VLDn (all lanes)
Date: Mon, 19 Apr 2021 13:22:48 -0700	[thread overview]
Message-ID: <20210419202257.161730-23-richard.henderson@linaro.org> (raw)
In-Reply-To: <20210419202257.161730-1-richard.henderson@linaro.org>

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v2: Fix alignment for n in {2, 4}.
---
 target/arm/translate.h          |  1 +
 target/arm/translate.c          | 15 +++++++++++++
 target/arm/translate-neon.c.inc | 37 +++++++++++++++++++++++++--------
 3 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/target/arm/translate.h b/target/arm/translate.h
index 0c60b83b3d..ccf60c96d8 100644
--- a/target/arm/translate.h
+++ b/target/arm/translate.h
@@ -204,6 +204,7 @@ void arm_test_cc(DisasCompare *cmp, int cc);
 void arm_free_cc(DisasCompare *cmp);
 void arm_jump_cc(DisasCompare *cmp, TCGLabel *label);
 void arm_gen_test_cc(int cc, TCGLabel *label);
+MemOp pow2_align(unsigned i);
 
 /* Return state of Alternate Half-precision flag, caller frees result */
 static inline TCGv_i32 get_ahp_flag(void)
diff --git a/target/arm/translate.c b/target/arm/translate.c
index 4decb2610e..0cf6da7e79 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -908,6 +908,21 @@ static inline void store_reg_from_load(DisasContext *s, int reg, TCGv_i32 var)
 #define IS_USER_ONLY 0
 #endif
 
+MemOp pow2_align(unsigned i)
+{
+    static const MemOp mop_align[] = {
+        0, MO_ALIGN_2, MO_ALIGN_4, MO_ALIGN_8, MO_ALIGN_16,
+        /*
+         * FIXME: TARGET_PAGE_BITS_MIN affects TLB_FLAGS_MASK such
+         * that 256-bit alignment (MO_ALIGN_32) cannot be supported:
+         * see get_alignment_bits(). Enforce only 128-bit alignment for now.
+         */
+        MO_ALIGN_16
+    };
+    g_assert(i < ARRAY_SIZE(mop_align));
+    return mop_align[i];
+}
+
 /*
  * Abstractions of "generate code to do a guest load/store for
  * AArch32", where a vaddr is always 32 bits (and is zero
diff --git a/target/arm/translate-neon.c.inc b/target/arm/translate-neon.c.inc
index 18d9042130..9c2b076027 100644
--- a/target/arm/translate-neon.c.inc
+++ b/target/arm/translate-neon.c.inc
@@ -522,6 +522,7 @@ static bool trans_VLD_all_lanes(DisasContext *s, arg_VLD_all_lanes *a)
     int size = a->size;
     int nregs = a->n + 1;
     TCGv_i32 addr, tmp;
+    MemOp mop, align;
 
     if (!arm_dc_feature(s, ARM_FEATURE_NEON)) {
         return false;
@@ -532,18 +533,33 @@ static bool trans_VLD_all_lanes(DisasContext *s, arg_VLD_all_lanes *a)
         return false;
     }
 
+    align = 0;
     if (size == 3) {
         if (nregs != 4 || a->a == 0) {
             return false;
         }
         /* For VLD4 size == 3 a == 1 means 32 bits at 16 byte alignment */
-        size = 2;
-    }
-    if (nregs == 1 && a->a == 1 && size == 0) {
-        return false;
-    }
-    if (nregs == 3 && a->a == 1) {
-        return false;
+        size = MO_32;
+        align = MO_ALIGN_16;
+    } else if (a->a) {
+        switch (nregs) {
+        case 1:
+            if (size == 0) {
+                return false;
+            }
+            align = MO_ALIGN;
+            break;
+        case 2:
+            align = pow2_align(size + 1);
+            break;
+        case 3:
+            return false;
+        case 4:
+            align = pow2_align(size + 2);
+            break;
+        default:
+            g_assert_not_reached();
+        }
     }
 
     if (!vfp_access_check(s)) {
@@ -556,12 +572,12 @@ static bool trans_VLD_all_lanes(DisasContext *s, arg_VLD_all_lanes *a)
      */
     stride = a->t ? 2 : 1;
     vec_size = nregs == 1 ? stride * 8 : 8;
-
+    mop = size | align;
     tmp = tcg_temp_new_i32();
     addr = tcg_temp_new_i32();
     load_reg_var(s, addr, a->rn);
     for (reg = 0; reg < nregs; reg++) {
-        gen_aa32_ld_i32(s, tmp, addr, get_mem_index(s), size);
+        gen_aa32_ld_i32(s, tmp, addr, get_mem_index(s), mop);
         if ((vd & 1) && vec_size == 16) {
             /*
              * We cannot write 16 bytes at once because the
@@ -577,6 +593,9 @@ static bool trans_VLD_all_lanes(DisasContext *s, arg_VLD_all_lanes *a)
         }
         tcg_gen_addi_i32(addr, addr, 1 << size);
         vd += stride;
+
+        /* Subsequent memory operations inherit alignment */
+        mop &= ~MO_AMASK;
     }
     tcg_temp_free_i32(tmp);
     tcg_temp_free_i32(addr);
-- 
2.25.1


