Index: regcprop.c
===================================================================
--- regcprop.c	(revision 204974)
+++ regcprop.c	(working copy)
@@ -747,6 +747,7 @@ copyprop_hardreg_forward_1 (basic_block 
       int n_ops, i, alt, predicated;
       bool is_asm, any_replacements;
       rtx set;
+      rtx link;
       bool replaced[MAX_RECOG_OPERANDS];
       bool changed = false;
       struct kill_set_value_data ksvd;
@@ -815,6 +816,23 @@ copyprop_hardreg_forward_1 (basic_block 
 	if (recog_op_alt[i][alt].earlyclobber)
 	  kill_value (recog_data.operand[i], vd);
 
+      /* If we have dead sets in the insn, then we need to note these as we
+	 would clobbers.  */
+      for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+	{
+	  if (REG_NOTE_KIND (link) == REG_UNUSED)
+	    {
+	      kill_value (XEXP (link, 0), vd);
+	      /* Furthermore, if the insn looked like a single-set,
+		 but the dead store kills the source value of that
+		 set, then we can no-longer use the plain move
+		 special case below.  */
+	      if (set
+		  && reg_overlap_mentioned_p (XEXP (link, 0), SET_SRC (set)))
+		set = NULL;
+	    }
+	}
+
       /* Special-case plain move instructions, since we may well
 	 be able to do the move from a different register class.  */
       if (set && REG_P (SET_SRC (set)))
Index: testsuite/gcc.target/arm/pr54300.C
===================================================================
--- testsuite/gcc.target/arm/pr54300.C	(revision 0)
+++ testsuite/gcc.target/arm/pr54300.C	(revision 0)
@@ -0,0 +1,61 @@
+/* { dg-do run } */
+/* { dg-require-effective-target arm_neon } */
+/* { dg-options "-O2" } */
+/* { dg-add-options arm_neon } */
+
+#include <arm_neon.h>
+#include <stdlib.h>
+
+struct __attribute__ ((aligned(8))) _v16u8_ {
+  uint8x16_t val;
+  _v16u8_( const int16x8_t &src) { val = vreinterpretq_u8_s16(src); }
+  operator int16x8_t () const { return vreinterpretq_s16_u8(val); }
+};
+typedef struct _v16u8_ v16u8;
+
+struct __attribute__ ((aligned(4))) _v8u8_ {
+  uint8x8_t val;
+  _v8u8_( const uint8x8_t &src) { val = src; }
+  operator int16x4_t () const { return vreinterpret_s16_u8(val); }
+};
+typedef struct _v8u8_ v8u8;
+
+typedef v16u8                v8i16;
+typedef int32x4_t            v4i32;
+typedef const short         cv1i16;
+typedef const unsigned char cv1u8;
+typedef const v8i16         cv8i16;
+
+static inline __attribute__((always_inline)) v8u8 zero_64(){ return vdup_n_u8( 0 ); }
+
+static inline __attribute__((always_inline)) v8i16 loadlo_8i16( cv8i16* p ){
+  return vcombine_s16( vld1_s16( (cv1i16 *)p ), zero_64() );
+}
+static inline __attribute__((always_inline)) v8i16 _loadlo_8i16( cv8i16* p, int offset ){
+  return loadlo_8i16( (cv8i16*)(&((cv1u8*)p)[offset]) );
+}
+
+void __attribute__((noinline))
+test(unsigned short *_Inp, int32_t *_Out,
+     unsigned int s1v, unsigned int dv0,
+     unsigned int smask_v)
+{
+  int32x4_t c = vdupq_n_s32(0);
+
+  for(unsigned int sv=0 ; sv!=dv0 ; sv=(sv+s1v)&smask_v )
+    {
+      int32x4_t s;
+      s = vmovl_s16( vget_low_s16( _loadlo_8i16( (cv8i16*) _Inp, sv ) ) );
+      c = vaddq_s32( c, s );
+    }
+  vst1q_s32( _Out, c );
+}
+
+main()
+{
+  unsigned short a[4] = {1, 2, 3, 4};
+  int32_t b[4] = {0, 0, 0, 0};
+  test(a, b, 1, 1, ~0);
+  if (b[0] != 1 || b[1] != 2 || b[2] != 3 || b[3] != 4)
+    abort();
+}