[Qemu-devel] [PULL 27/52] target-arm: A64: Fix vector register access on bigendian hosts

[Peter Maydell <peter.maydell@linaro.org>]

The A64 128 bit vector registers are stored as a pair of
uint64_t values in the register array. This means that if
we're directly loading or storing a value of size less than
64 bits we must adjust the offset appropriately to account
for whether the host is bigendian or not. Provide utility
functions to abstract away the offsetof() calculations for
the FP registers.

For do_fp_st() we can sidestep most of the issues for 64 bit
and smaller reg-to-mem transfers by always doing a 64 bit
load from the register and writing just the piece we need
to memory.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
---
 target-arm/translate-a64.c | 69 +++++++++++++++++++++++-----------------------
 1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
index 326f36d..ba9573a 100644
--- a/target-arm/translate-a64.c
+++ b/target-arm/translate-a64.c
@@ -308,6 +308,26 @@ static TCGv_i64 read_cpu_reg_sp(DisasContext *s, int reg, int sf)
     return v;
 }
 
+/* Return the offset into CPUARMState of a slice (from
+ * the least significant end) of FP register Qn (ie
+ * Dn, Sn, Hn or Bn).
+ * (Note that this is not the same mapping as for A32; see cpu.h)
+ */
+static inline int fp_reg_offset(int regno, TCGMemOp size)
+{
+    int offs = offsetof(CPUARMState, vfp.regs[regno * 2]);
+#ifdef HOST_WORDS_BIGENDIAN
+    offs += (8 - (1 << size));
+#endif
+    return offs;
+}
+
+/* Offset of the high half of the 128 bit vector Qn */
+static inline int fp_reg_hi_offset(int regno)
+{
+    return offsetof(CPUARMState, vfp.regs[regno * 2 + 1]);
+}
+
 /* Set ZF and NF based on a 64 bit result. This is alas fiddlier
  * than the 32 bit equivalent.
  */
@@ -538,31 +558,15 @@ static void do_gpr_ld(DisasContext *s, TCGv_i64 dest, TCGv_i64 tcg_addr,
 static void do_fp_st(DisasContext *s, int srcidx, TCGv_i64 tcg_addr, int size)
 {
     /* This writes the bottom N bits of a 128 bit wide vector to memory */
-    int freg_offs = offsetof(CPUARMState, vfp.regs[srcidx * 2]);
     TCGv_i64 tmp = tcg_temp_new_i64();
-
+    tcg_gen_ld_i64(tmp, cpu_env, fp_reg_offset(srcidx, MO_64));
     if (size < 4) {
-        switch (size) {
-        case 0:
-            tcg_gen_ld8u_i64(tmp, cpu_env, freg_offs);
-            break;
-        case 1:
-            tcg_gen_ld16u_i64(tmp, cpu_env, freg_offs);
-            break;
-        case 2:
-            tcg_gen_ld32u_i64(tmp, cpu_env, freg_offs);
-            break;
-        case 3:
-            tcg_gen_ld_i64(tmp, cpu_env, freg_offs);
-            break;
-        }
         tcg_gen_qemu_st_i64(tmp, tcg_addr, get_mem_index(s), MO_TE + size);
     } else {
         TCGv_i64 tcg_hiaddr = tcg_temp_new_i64();
-        tcg_gen_ld_i64(tmp, cpu_env, freg_offs);
         tcg_gen_qemu_st_i64(tmp, tcg_addr, get_mem_index(s), MO_TEQ);
         tcg_gen_qemu_st64(tmp, tcg_addr, get_mem_index(s));
-        tcg_gen_ld_i64(tmp, cpu_env, freg_offs + sizeof(float64));
+        tcg_gen_ld_i64(tmp, cpu_env, fp_reg_hi_offset(srcidx));
         tcg_gen_addi_i64(tcg_hiaddr, tcg_addr, 8);
         tcg_gen_qemu_st_i64(tmp, tcg_hiaddr, get_mem_index(s), MO_TEQ);
         tcg_temp_free_i64(tcg_hiaddr);
@@ -577,7 +581,6 @@ static void do_fp_st(DisasContext *s, int srcidx, TCGv_i64 tcg_addr, int size)
 static void do_fp_ld(DisasContext *s, int destidx, TCGv_i64 tcg_addr, int size)
 {
     /* This always zero-extends and writes to a full 128 bit wide vector */
-    int freg_offs = offsetof(CPUARMState, vfp.regs[destidx * 2]);
     TCGv_i64 tmplo = tcg_temp_new_i64();
     TCGv_i64 tmphi;
 
@@ -596,8 +599,8 @@ static void do_fp_ld(DisasContext *s, int destidx, TCGv_i64 tcg_addr, int size)
         tcg_temp_free_i64(tcg_hiaddr);
     }
 
-    tcg_gen_st_i64(tmplo, cpu_env, freg_offs);
-    tcg_gen_st_i64(tmphi, cpu_env, freg_offs + sizeof(float64));
+    tcg_gen_st_i64(tmplo, cpu_env, fp_reg_offset(destidx, MO_64));
+    tcg_gen_st_i64(tmphi, cpu_env, fp_reg_hi_offset(destidx));
 
     tcg_temp_free_i64(tmplo);
     tcg_temp_free_i64(tmphi);
@@ -3224,7 +3227,6 @@ static void handle_fmov(DisasContext *s, int rd, int rn, int type, bool itof)
      */
 
     if (itof) {
-        int freg_offs = offsetof(CPUARMState, vfp.regs[rd * 2]);
         TCGv_i64 tcg_rn = cpu_reg(s, rn);
 
         switch (type) {
@@ -3233,9 +3235,9 @@ static void handle_fmov(DisasContext *s, int rd, int rn, int type, bool itof)
             /* 32 bit */
             TCGv_i64 tmp = tcg_temp_new_i64();
             tcg_gen_ext32u_i64(tmp, tcg_rn);
-            tcg_gen_st_i64(tmp, cpu_env, freg_offs);
+            tcg_gen_st_i64(tmp, cpu_env, fp_reg_offset(rd, MO_64));
             tcg_gen_movi_i64(tmp, 0);
-            tcg_gen_st_i64(tmp, cpu_env, freg_offs + sizeof(float64));
+            tcg_gen_st_i64(tmp, cpu_env, fp_reg_hi_offset(rd));
             tcg_temp_free_i64(tmp);
             break;
         }
@@ -3243,32 +3245,31 @@ static void handle_fmov(DisasContext *s, int rd, int rn, int type, bool itof)
         {
             /* 64 bit */
             TCGv_i64 tmp = tcg_const_i64(0);
-            tcg_gen_st_i64(tcg_rn, cpu_env, freg_offs);
-            tcg_gen_st_i64(tmp, cpu_env, freg_offs + sizeof(float64));
+            tcg_gen_st_i64(tcg_rn, cpu_env, fp_reg_offset(rd, MO_64));
+            tcg_gen_st_i64(tmp, cpu_env, fp_reg_hi_offset(rd));
             tcg_temp_free_i64(tmp);
             break;
         }
         case 2:
             /* 64 bit to top half. */
-            tcg_gen_st_i64(tcg_rn, cpu_env, freg_offs + sizeof(float64));
+            tcg_gen_st_i64(tcg_rn, cpu_env, fp_reg_hi_offset(rd));
             break;
         }
     } else {
-        int freg_offs = offsetof(CPUARMState, vfp.regs[rn * 2]);
         TCGv_i64 tcg_rd = cpu_reg(s, rd);
 
         switch (type) {
         case 0:
             /* 32 bit */
-            tcg_gen_ld32u_i64(tcg_rd, cpu_env, freg_offs);
+            tcg_gen_ld32u_i64(tcg_rd, cpu_env, fp_reg_offset(rn, MO_32));
             break;
-        case 2:
-            /* 64 bits from top half */
-            freg_offs += sizeof(float64);
-            /* fall through */
         case 1:
             /* 64 bit */
-            tcg_gen_ld_i64(tcg_rd, cpu_env, freg_offs);
+            tcg_gen_ld_i64(tcg_rd, cpu_env, fp_reg_offset(rn, MO_64));
+            break;
+        case 2:
+            /* 64 bits from top half */
+            tcg_gen_ld_i64(tcg_rd, cpu_env, fp_reg_hi_offset(rn));
             break;
         }
     }
-- 
1.8.5