target/arm: Implement GCSPOPM

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20251008215613.300150-50-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpregs-gcs.c

@@ -100,6 +100,9 @@ static const ARMCPRegInfo gcs_reginfo[] = {
       .opc0 = 1, .opc1 = 3, .crn = 7, .crm = 7, .opc2 = 0,
       .access = PL0_W, .accessfn = access_gcspushm,
       .fgt = FGT_NGCSPUSHM_EL1, .type = ARM_CP_GCSPUSHM },
+    { .name = "GCSPOPM", .state = ARM_CP_STATE_AA64,
+      .opc0 = 1, .opc1 = 3, .crn = 7, .crm = 7, .opc2 = 1,
+      .access = PL0_R, .type = ARM_CP_GCSPOPM },
 };
 
 void define_gcs_cpregs(ARMCPU *cpu)

target/arm/cpregs.h

@@ -49,6 +49,7 @@ enum {
     ARM_CP_DC_GZVA               = 0x0007,
     /* Special: gcs instructions */
     ARM_CP_GCSPUSHM              = 0x0008,
+    ARM_CP_GCSPOPM               = 0x0009,
 
     /* Flag: reads produce resetvalue; writes ignored. */
     ARM_CP_CONST                 = 1 << 4,

target/arm/tcg/translate-a64.c

@@ -2521,6 +2521,24 @@ static void gen_sysreg_undef(DisasContext *s, bool isread,
     gen_exception_insn(s, 0, EXCP_UDEF, syndrome);
 }
 
+static void gen_gcspopm(DisasContext *s, int rt)
+{
+    TCGv_i64 gcspr = cpu_gcspr[s->current_el];
+    int mmuidx = core_gcs_mem_index(s->mmu_idx);
+    MemOp mop = finalize_memop(s, MO_64 | MO_ALIGN);
+    TCGv_i64 value = tcg_temp_new_i64();
+    TCGLabel *fail_label =
+        delay_exception(s, EXCP_UDEF, syn_gcs_data_check(GCS_IT_GCSPOPM, rt));
+
+    /* The value at top-of-stack must have low 2 bits clear. */
+    tcg_gen_qemu_ld_i64(value, clean_data_tbi(s, gcspr), mmuidx, mop);
+    tcg_gen_brcondi_i64(TCG_COND_TSTNE, value, 3, fail_label);
+
+    /* Complete the pop and return the value. */
+    tcg_gen_addi_i64(gcspr, gcspr, 8);
+    tcg_gen_mov_i64(cpu_reg(s, rt), value);
+}
+
 /*
  * Look up @key, returning the cpreg, which must exist.
  * Additionally, the new cpreg must also be accessible.
@@ -2832,6 +2850,12 @@ static void handle_sys(DisasContext *s, bool isread,
             gen_add_gcs_record(s, cpu_reg(s, rt));
         }
         return;
+    case ARM_CP_GCSPOPM:
+        /* Note that X[rt] is unchanged if !GCSEnabled. */
+        if (s->gcs_en) {
+            gen_gcspopm(s, rt);
+        }
+        return;
     default:
         g_assert_not_reached();
     }