arm: big-endian issue in gen_cpymem_ldrd_strd [PR105981]

The code in gen_cpymem_ldrd_strd has been incorrect for big-endian
since r230663.  The problem is that we use gen_lowpart, etc. to split
the 64-bit quantity, but fail to account for the fact that these
routines are really dealing with 64-bit /values/ and in big-endian the
ordering of the sub-registers changes.

To fix this, I've renamed the conceptually misnamed low_reg and hi_reg
as first_reg and second_reg, and then used different logic for
big-endian targets to initialize these values.  This makes the logic
clearer than trying to think about high bits and low bits.

gcc/ChangeLog:

	PR target/105981
	* config/arm/arm.c (gen_cpymem_ldrd_strd): Rename low_reg and hi_reg
	to first_reg and second_reg respectively.  Initialize them correctly
	when generating big-endian code.

(cherry picked from commit 8aaa948059a8b5f0a62ad010d0aa6346b7ac9cd3)

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 9e549285d0ca3c7dfaf26f1fc3b2b7a0a94a963c..730b1fe0071b270f94d4ada1448b4fddef2b7a58 100644 (file)
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -15546,13 +15546,21 @@ gen_cpymem_ldrd_strd (rtx *operands)
     {
       len -= 8;
       reg0 = gen_reg_rtx (DImode);
-      rtx low_reg = NULL_RTX;
-      rtx hi_reg = NULL_RTX;
+      rtx first_reg = NULL_RTX;
+      rtx second_reg = NULL_RTX;
 
       if (!src_aligned || !dst_aligned)
        {
-         low_reg = gen_lowpart (SImode, reg0);
-         hi_reg = gen_highpart_mode (SImode, DImode, reg0);
+         if (BYTES_BIG_ENDIAN)
+           {
+             second_reg = gen_lowpart (SImode, reg0);
+             first_reg = gen_highpart_mode (SImode, DImode, reg0);
+           }
+         else
+           {
+             first_reg = gen_lowpart (SImode, reg0);
+             second_reg = gen_highpart_mode (SImode, DImode, reg0);
+           }
        }
       if (MEM_ALIGN (src) >= 2 * BITS_PER_WORD)
        emit_move_insn (reg0, src);
@@ -15560,9 +15568,9 @@ gen_cpymem_ldrd_strd (rtx *operands)
        emit_insn (gen_unaligned_loaddi (reg0, src));
       else
        {
-         emit_insn (gen_unaligned_loadsi (low_reg, src));
+         emit_insn (gen_unaligned_loadsi (first_reg, src));
          src = next_consecutive_mem (src);
-         emit_insn (gen_unaligned_loadsi (hi_reg, src));
+         emit_insn (gen_unaligned_loadsi (second_reg, src));
        }
 
       if (MEM_ALIGN (dst) >= 2 * BITS_PER_WORD)
@@ -15571,9 +15579,9 @@ gen_cpymem_ldrd_strd (rtx *operands)
        emit_insn (gen_unaligned_storedi (dst, reg0));
       else
        {
-         emit_insn (gen_unaligned_storesi (dst, low_reg));
+         emit_insn (gen_unaligned_storesi (dst, first_reg));
          dst = next_consecutive_mem (dst);
-         emit_insn (gen_unaligned_storesi (dst, hi_reg));
+         emit_insn (gen_unaligned_storesi (dst, second_reg));
        }
 
       src = next_consecutive_mem (src);