diff --git a/cranelift/codegen/src/isa/s390x/lower.isle b/cranelift/codegen/src/isa/s390x/lower.isle
index 1db1e8de32..fb6170c797 100644
--- a/cranelift/codegen/src/isa/s390x/lower.isle
+++ b/cranelift/codegen/src/isa/s390x/lower.isle
@@ -408,8 +408,8 @@
             (y_hi Reg (vec_extract_lane $I64X2 y 0 (zero_reg)))
             (y_lo Reg (vec_extract_lane $I64X2 y 1 (zero_reg)))
             (lo_pair RegPair (umul_wide x_lo y_lo))
-            (res_lo Reg (copy_reg $I64 (regpair_lo lo_pair)))
-            (res_hi_1 Reg (copy_reg $I64 (regpair_hi lo_pair)))
+            (res_lo Reg (regpair_lo lo_pair))
+            (res_hi_1 Reg (regpair_hi lo_pair))
             (res_hi_2 Reg (mul_reg $I64 x_lo y_hi))
             (res_hi_3 Reg (mul_reg $I64 x_hi y_lo))
             (res_hi Reg (add_reg $I64 res_hi_3 (add_reg $I64 res_hi_2 res_hi_1))))
@@ -435,7 +435,7 @@
 ;; Multiply high part unsigned, 64-bit types.  (Uses umul_wide.)
 (rule (lower (has_type $I64 (umulhi x y)))
       (let ((pair RegPair (umul_wide x y)))
-        (copy_reg $I64 (regpair_hi pair))))
+        (regpair_hi pair)))
 
 ;; Multiply high part unsigned, vector types with 8-, 16-, or 32-bit elements.
 (rule (lower (has_type $I8X16 (umulhi x y))) (vec_umulhi $I8X16 x y))
@@ -447,10 +447,10 @@
 (rule (lower (has_type $I64X2 (umulhi x y)))
       (let ((pair_0 RegPair (umul_wide (vec_extract_lane $I64X2 x 0 (zero_reg))
                                        (vec_extract_lane $I64X2 y 0 (zero_reg))))
-            (res_0 Reg (copy_reg $I64 (regpair_hi pair_0)))
+            (res_0 Reg (regpair_hi pair_0))
             (pair_1 RegPair (umul_wide (vec_extract_lane $I64X2 x 1 (zero_reg))
                                        (vec_extract_lane $I64X2 y 1 (zero_reg))))
-            (res_1 Reg (copy_reg $I64 (regpair_hi pair_1))))
+            (res_1 Reg (regpair_hi pair_1)))
         (mov_to_vec128 $I64X2 res_0 res_1)))
 
 
@@ -473,7 +473,7 @@
 ;; Multiply high part signed, 64-bit types.  (Uses smul_wide.)
 (rule (lower (has_type $I64 (smulhi x y)))
       (let ((pair RegPair (smul_wide x y)))
-        (copy_reg $I64 (regpair_hi pair))))
+        (regpair_hi pair)))
 
 ;; Multiply high part signed, vector types with 8-, 16-, or 32-bit elements.
 (rule (lower (has_type $I8X16 (smulhi x y))) (vec_smulhi $I8X16 x y))
@@ -488,7 +488,7 @@
             (res_0 Reg (copy_reg $I64 (regpair_hi pair_0)))
             (pair_1 RegPair (smul_wide (vec_extract_lane $I64X2 x 1 (zero_reg))
                                        (vec_extract_lane $I64X2 y 1 (zero_reg))))
-            (res_1 Reg (copy_reg $I64 (regpair_hi pair_1))))
+            (res_1 Reg (regpair_hi pair_1)))
         (mov_to_vec128 $I64X2 res_0 res_1)))
 
 
@@ -547,7 +547,7 @@
             ;; Emit the actual divide instruction.
             (pair RegPair (udivmod ext_ty ext_x ext_y)))
         ;; The quotient can be found in the low half of the result.
-        (copy_reg ty (regpair_lo pair))))
+        (regpair_lo pair)))
 
 ;; Implement `urem`.  Same as `udiv`, but finds the remainder in
 ;; the high half of the result register pair instead.
@@ -557,7 +557,7 @@
             (ext_y Reg (put_in_reg_zext32 y))
             (ext_ty Type (ty_ext32 ty))
             (pair RegPair (udivmod ext_ty ext_x ext_y)))
-        (copy_reg ty (regpair_hi pair))))
+        (regpair_hi pair)))
 
 
 ;;;; Rules for `sdiv` and `srem` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -591,7 +591,7 @@
             ;; Emit the actual divide instruction.
             (pair RegPair (sdivmod ext_ty ext_x ext_y)))
         ;; The quotient can be found in the low half of the result.
-        (copy_reg ty (regpair_lo pair))))
+        (regpair_lo pair)))
 
 ;; Implement `srem`.  Same as `sdiv`, but finds the remainder in
 ;; the high half of the result register pair instead.  Also, handle
@@ -603,7 +603,7 @@
             (ext_ty Type (ty_ext32 ty))
             (checked_x Reg (maybe_avoid_srem_overflow OFcheck ext_ty ext_x ext_y))
             (pair RegPair (sdivmod ext_ty checked_x ext_y)))
-        (copy_reg ty (regpair_hi pair))))
+        (regpair_hi pair)))
 
 ;; Determine whether we need to perform an integer-overflow check.
 ;;
@@ -1190,7 +1190,7 @@
 (rule (clz_offset $I8 x) (add_simm16 $I8 x -56))
 (rule (clz_offset $I16 x) (add_simm16 $I16 x -48))
 (rule (clz_offset $I32 x) (add_simm16 $I32 x -32))
-(rule (clz_offset $I64 x) (copy_reg $I64 x))
+(rule (clz_offset $I64 x) x)
 
 ;; Count leading zeros, via FLOGR on an input zero-extended to 64 bits,
 ;; with the result compensated for the extra bits.
diff --git a/cranelift/filetests/filetests/isa/s390x/arithmetic.clif b/cranelift/filetests/filetests/isa/s390x/arithmetic.clif
index 8803998743..3befae30a3 100644
--- a/cranelift/filetests/filetests/isa/s390x/arithmetic.clif
+++ b/cranelift/filetests/filetests/isa/s390x/arithmetic.clif
@@ -944,9 +944,9 @@ block0(v0: i128, v1: i128):
 }
 
 ; VCode:
-;   stmg %r7, %r15, 56(%r15)
+;   stmg %r6, %r15, 48(%r15)
 ; block0:
-;   lgr %r10, %r2
+;   lgr %r6, %r2
 ;   vl %v1, 0(%r3)
 ;   vl %v3, 0(%r4)
 ;   lgdr %r4, %f1
@@ -955,22 +955,21 @@ block0(v0: i128, v1: i128):
 ;   vlgvg %r9, %v3, 1
 ;   lgr %r3, %r5
 ;   mlgr %r2, %r9
-;   lgr %r8, %r2
-;   msgrkc %r2, %r5, %r7
+;   msgrkc %r14, %r5, %r7
 ;   msgrkc %r5, %r4, %r9
-;   agrk %r4, %r2, %r8
+;   agrk %r4, %r14, %r2
 ;   agr %r5, %r4
-;   vlvgp %v5, %r5, %r3
-;   lgr %r2, %r10
-;   vst %v5, 0(%r2)
-;   lmg %r7, %r15, 56(%r15)
+;   vlvgp %v1, %r5, %r3
+;   lgr %r2, %r6
+;   vst %v1, 0(%r2)
+;   lmg %r6, %r15, 48(%r15)
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   stmg %r7, %r15, 0x38(%r15)
+;   stmg %r6, %r15, 0x30(%r15)
 ; block1: ; offset 0x6
-;   lgr %r10, %r2
+;   lgr %r6, %r2
 ;   vl %v1, 0(%r3)
 ;   vl %v3, 0(%r4)
 ;   lgdr %r4, %f1
@@ -979,15 +978,14 @@ block0(v0: i128, v1: i128):
 ;   vlgvg %r9, %v3, 1
 ;   lgr %r3, %r5
 ;   mlgr %r2, %r9
-;   lgr %r8, %r2
-;   msgrkc %r2, %r5, %r7
+;   msgrkc %r14, %r5, %r7
 ;   msgrkc %r5, %r4, %r9
-;   agrk %r4, %r2, %r8
+;   agrk %r4, %r14, %r2
 ;   agr %r5, %r4
-;   vlvgp %v5, %r5, %r3
-;   lgr %r2, %r10
-;   vst %v5, 0(%r2)
-;   lmg %r7, %r15, 0x38(%r15)
+;   vlvgp %v1, %r5, %r3
+;   lgr %r2, %r6
+;   vst %v1, 0(%r2)
+;   lmg %r6, %r15, 0x30(%r15)
 ;   br %r14
 
 function %imul_i64(i64, i64) -> i64 {
@@ -1319,16 +1317,16 @@ block0(v0: i64, v1: i64):
 
 ; VCode:
 ; block0:
-;   lgr %r5, %r3
+;   lgr %r4, %r3
 ;   lgr %r3, %r2
-;   mlgr %r2, %r5
+;   mlgr %r2, %r4
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   lgr %r5, %r3
+;   lgr %r4, %r3
 ;   lgr %r3, %r2
-;   mlgr %r2, %r5
+;   mlgr %r2, %r4
 ;   br %r14
 
 function %umulhi_i32(i32, i32) -> i32 {
@@ -1541,34 +1539,34 @@ block0(v0: i32, v1: i32):
 }
 
 ; VCode:
-;   stmg %r7, %r15, 56(%r15)
+;   stmg %r6, %r15, 48(%r15)
 ; block0:
-;   lgr %r7, %r3
+;   lgr %r6, %r3
 ;   lgfr %r3, %r2
 ;   iilf %r4, 2147483647
 ;   xrk %r5, %r4, %r3
-;   lgr %r4, %r7
-;   nr %r5, %r4
-;   cite %r5, -1
-;   dsgfr %r2, %r4
+;   lgr %r2, %r6
+;   nrk %r4, %r5, %r2
+;   cite %r4, -1
+;   dsgfr %r2, %r2
 ;   lgr %r2, %r3
-;   lmg %r7, %r15, 56(%r15)
+;   lmg %r6, %r15, 48(%r15)
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   stmg %r7, %r15, 0x38(%r15)
+;   stmg %r6, %r15, 0x30(%r15)
 ; block1: ; offset 0x6
-;   lgr %r7, %r3
+;   lgr %r6, %r3
 ;   lgfr %r3, %r2
 ;   iilf %r4, 0x7fffffff
 ;   xrk %r5, %r4, %r3
-;   lgr %r4, %r7
-;   nr %r5, %r4
-;   cite %r5, -1 ; trap: int_ovf
-;   dsgfr %r2, %r4 ; trap: int_divz
+;   lgr %r2, %r6
+;   nrk %r4, %r5, %r2
+;   cite %r4, -1 ; trap: int_ovf
+;   dsgfr %r2, %r2 ; trap: int_divz
 ;   lgr %r2, %r3
-;   lmg %r7, %r15, 0x38(%r15)
+;   lmg %r6, %r15, 0x30(%r15)
 ;   br %r14
 
 function %sdiv_i32_imm(i32) -> i32 {
@@ -1813,34 +1811,32 @@ block0(v0: i16, v1: i16):
 }
 
 ; VCode:
-;   stmg %r8, %r15, 64(%r15)
+;   stmg %r7, %r15, 56(%r15)
 ; block0:
 ;   lgr %r4, %r3
 ;   lhi %r5, 0
-;   lgr %r8, %r5
+;   lgr %r7, %r5
 ;   llhr %r3, %r2
-;   lgr %r5, %r4
-;   llhr %r5, %r5
-;   lgr %r2, %r8
+;   llhr %r5, %r4
+;   lgr %r2, %r7
 ;   dlr %r2, %r5
 ;   lgr %r2, %r3
-;   lmg %r8, %r15, 64(%r15)
+;   lmg %r7, %r15, 56(%r15)
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   stmg %r8, %r15, 0x40(%r15)
+;   stmg %r7, %r15, 0x38(%r15)
 ; block1: ; offset 0x6
 ;   lgr %r4, %r3
 ;   lhi %r5, 0
-;   lgr %r8, %r5
+;   lgr %r7, %r5
 ;   llhr %r3, %r2
-;   lgr %r5, %r4
-;   llhr %r5, %r5
-;   lgr %r2, %r8
+;   llhr %r5, %r4
+;   lgr %r2, %r7
 ;   dlr %r2, %r5 ; trap: int_divz
 ;   lgr %r2, %r3
-;   lmg %r8, %r15, 0x40(%r15)
+;   lmg %r7, %r15, 0x38(%r15)
 ;   br %r14
 
 function %udiv_i16_imm(i16) -> i16 {
@@ -1879,34 +1875,32 @@ block0(v0: i8, v1: i8):
 }
 
 ; VCode:
-;   stmg %r8, %r15, 64(%r15)
+;   stmg %r7, %r15, 56(%r15)
 ; block0:
 ;   lgr %r4, %r3
 ;   lhi %r5, 0
-;   lgr %r8, %r5
+;   lgr %r7, %r5
 ;   llcr %r3, %r2
-;   lgr %r5, %r4
-;   llcr %r5, %r5
-;   lgr %r2, %r8
+;   llcr %r5, %r4
+;   lgr %r2, %r7
 ;   dlr %r2, %r5
 ;   lgr %r2, %r3
-;   lmg %r8, %r15, 64(%r15)
+;   lmg %r7, %r15, 56(%r15)
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   stmg %r8, %r15, 0x40(%r15)
+;   stmg %r7, %r15, 0x38(%r15)
 ; block1: ; offset 0x6
 ;   lgr %r4, %r3
 ;   lhi %r5, 0
-;   lgr %r8, %r5
+;   lgr %r7, %r5
 ;   llcr %r3, %r2
-;   lgr %r5, %r4
-;   llcr %r5, %r5
-;   lgr %r2, %r8
+;   llcr %r5, %r4
+;   lgr %r2, %r7
 ;   dlr %r2, %r5 ; trap: int_divz
 ;   lgr %r2, %r3
-;   lmg %r8, %r15, 0x40(%r15)
+;   lmg %r7, %r15, 0x38(%r15)
 ;   br %r14
 
 function %udiv_i8_imm(i8) -> i8 {
@@ -1950,7 +1944,8 @@ block0(v0: i64, v1: i64):
 ;   lgr %r4, %r3
 ;   lgr %r3, %r2
 ;   locghie %r3, 0
-;   dsgr %r2, %r4
+;   lgr %r2, %r4
+;   dsgr %r2, %r2
 ;   br %r14
 ; 
 ; Disassembled:
@@ -1959,7 +1954,8 @@ block0(v0: i64, v1: i64):
 ;   lgr %r4, %r3
 ;   lgr %r3, %r2
 ;   locghie %r3, 0
-;   dsgr %r2, %r4 ; trap: int_divz
+;   lgr %r2, %r4
+;   dsgr %r2, %r2 ; trap: int_divz
 ;   br %r14
 
 function %srem_i32(i32, i32) -> i32 {
@@ -1972,16 +1968,14 @@ block0(v0: i32, v1: i32):
 ; block0:
 ;   lgr %r5, %r3
 ;   lgfr %r3, %r2
-;   lgr %r2, %r5
-;   dsgfr %r2, %r2
+;   dsgfr %r2, %r5
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
 ;   lgr %r5, %r3
 ;   lgfr %r3, %r2
-;   lgr %r2, %r5
-;   dsgfr %r2, %r2 ; trap: int_divz
+;   dsgfr %r2, %r5 ; trap: int_divz
 ;   br %r14
 
 function %srem_i16(i16, i16) -> i16 {
@@ -1992,17 +1986,19 @@ block0(v0: i16, v1: i16):
 
 ; VCode:
 ; block0:
-;   lgr %r4, %r3
+;   lgr %r5, %r3
 ;   lghr %r3, %r2
-;   lhr %r4, %r4
+;   lgr %r2, %r5
+;   lhr %r4, %r2
 ;   dsgfr %r2, %r4
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   lgr %r4, %r3
+;   lgr %r5, %r3
 ;   lghr %r3, %r2
-;   lhr %r4, %r4
+;   lgr %r2, %r5
+;   lhr %r4, %r2
 ;   dsgfr %r2, %r4 ; trap: int_divz
 ;   br %r14
 
@@ -2014,17 +2010,19 @@ block0(v0: i8, v1: i8):
 
 ; VCode:
 ; block0:
-;   lgr %r4, %r3
+;   lgr %r5, %r3
 ;   lgbr %r3, %r2
-;   lbr %r4, %r4
+;   lgr %r2, %r5
+;   lbr %r4, %r2
 ;   dsgfr %r2, %r4
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   lgr %r4, %r3
+;   lgr %r5, %r3
 ;   lgbr %r3, %r2
-;   lbr %r4, %r4
+;   lgr %r2, %r5
+;   lbr %r4, %r2
 ;   dsgfr %r2, %r4 ; trap: int_divz
 ;   br %r14
 
@@ -2079,32 +2077,30 @@ block0(v0: i16, v1: i16):
 }
 
 ; VCode:
-;   stmg %r8, %r15, 64(%r15)
+;   stmg %r7, %r15, 56(%r15)
 ; block0:
 ;   lgr %r4, %r3
 ;   lhi %r5, 0
-;   lgr %r8, %r5
+;   lgr %r7, %r5
 ;   llhr %r3, %r2
-;   lgr %r5, %r4
-;   llhr %r5, %r5
-;   lgr %r2, %r8
+;   llhr %r5, %r4
+;   lgr %r2, %r7
 ;   dlr %r2, %r5
-;   lmg %r8, %r15, 64(%r15)
+;   lmg %r7, %r15, 56(%r15)
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   stmg %r8, %r15, 0x40(%r15)
+;   stmg %r7, %r15, 0x38(%r15)
 ; block1: ; offset 0x6
 ;   lgr %r4, %r3
 ;   lhi %r5, 0
-;   lgr %r8, %r5
+;   lgr %r7, %r5
 ;   llhr %r3, %r2
-;   lgr %r5, %r4
-;   llhr %r5, %r5
-;   lgr %r2, %r8
+;   llhr %r5, %r4
+;   lgr %r2, %r7
 ;   dlr %r2, %r5 ; trap: int_divz
-;   lmg %r8, %r15, 0x40(%r15)
+;   lmg %r7, %r15, 0x38(%r15)
 ;   br %r14
 
 function %urem_i8(i8, i8) -> i8 {
@@ -2114,31 +2110,29 @@ block0(v0: i8, v1: i8):
 }
 
 ; VCode:
-;   stmg %r8, %r15, 64(%r15)
+;   stmg %r7, %r15, 56(%r15)
 ; block0:
 ;   lgr %r4, %r3
 ;   lhi %r5, 0
-;   lgr %r8, %r5
+;   lgr %r7, %r5
 ;   llcr %r3, %r2
-;   lgr %r5, %r4
-;   llcr %r5, %r5
-;   lgr %r2, %r8
+;   llcr %r5, %r4
+;   lgr %r2, %r7
 ;   dlr %r2, %r5
-;   lmg %r8, %r15, 64(%r15)
+;   lmg %r7, %r15, 56(%r15)
 ;   br %r14
 ; 
 ; Disassembled:
 ; block0: ; offset 0x0
-;   stmg %r8, %r15, 0x40(%r15)
+;   stmg %r7, %r15, 0x38(%r15)
 ; block1: ; offset 0x6
 ;   lgr %r4, %r3
 ;   lhi %r5, 0
-;   lgr %r8, %r5
+;   lgr %r7, %r5
 ;   llcr %r3, %r2
-;   lgr %r5, %r4
-;   llcr %r5, %r5
-;   lgr %r2, %r8
+;   llcr %r5, %r4
+;   lgr %r2, %r7
 ;   dlr %r2, %r5 ; trap: int_divz
-;   lmg %r8, %r15, 0x40(%r15)
+;   lmg %r7, %r15, 0x38(%r15)
 ;   br %r14
 
diff --git a/cranelift/filetests/filetests/isa/s390x/vec-arithmetic.clif b/cranelift/filetests/filetests/isa/s390x/vec-arithmetic.clif
index 960477cbbd..d1074b3d2b 100644
--- a/cranelift/filetests/filetests/isa/s390x/vec-arithmetic.clif
+++ b/cranelift/filetests/filetests/isa/s390x/vec-arithmetic.clif
@@ -1148,11 +1148,11 @@ block0(v0: i64x2, v1: i64x2):
 ;   vlgvg %r3, %v24, 0
 ;   vlgvg %r4, %v25, 0
 ;   mlgr %r2, %r4
-;   lgr %r5, %r2
+;   lgr %r4, %r2
 ;   vlgvg %r3, %v24, 1
-;   vlgvg %r4, %v25, 1
-;   mlgr %r2, %r4
-;   vlvgp %v24, %r5, %r2
+;   vlgvg %r2, %v25, 1
+;   mlgr %r2, %r2
+;   vlvgp %v24, %r4, %r2
 ;   br %r14
 ; 
 ; Disassembled:
@@ -1160,11 +1160,11 @@ block0(v0: i64x2, v1: i64x2):
 ;   vlgvg %r3, %v24, 0
 ;   vlgvg %r4, %v25, 0
 ;   mlgr %r2, %r4
-;   lgr %r5, %r2
+;   lgr %r4, %r2
 ;   vlgvg %r3, %v24, 1
-;   vlgvg %r4, %v25, 1
-;   mlgr %r2, %r4
-;   vlvgp %v24, %r5, %r2
+;   vlgvg %r2, %v25, 1
+;   mlgr %r2, %r2
+;   vlvgp %v24, %r4, %r2
 ;   br %r14
 
 function %umulhi_i32x4(i32x4, i32x4) -> i32x4 {