fix issue 4996. (#5003)

cranelift/filetests/filetests/isa/riscv64/bitops.clif

@@ -120,7 +120,7 @@ block0(v0: i128):
 ;   li t0,64
 ;   select_reg t2,t3,zero##condition=(t0 eq a4)
 ;   add a0,a4,t2
-;   mv a1,zero
+;   li a1,0
 ;   ret
 
 function %c(i8) -> i8 {
@@ -194,8 +194,9 @@ block0(v0: i128):
 ;   li a5,64
 ;   select_reg a7,a3,zero##condition=(a5 eq t2)
 ;   add t4,t2,a7
+;   li t1,0
 ;   addi a0,t4,-1
-;   mv a1,zero
+;   li a1,0
 ;   ret
 
 function %d(i8) -> i8 {
@@ -254,7 +255,7 @@ block0(v0: i128):
 ;   li t0,64
 ;   select_reg t2,t3,zero##condition=(t0 eq a4)
 ;   add a0,a4,t2
-;   mv a1,zero
+;   li a1,0
 ;   ret
 
 function %d(i128) -> i128 {
@@ -267,7 +268,7 @@ block0(v0: i128):
 ;   popcnt a4,a0##ty=i64 tmp=a2 step=a3
 ;   popcnt t3,a1##ty=i64 tmp=a6 step=a7
 ;   add a0,a4,t3
-;   mv a1,zero
+;   li a1,0
 ;   ret
 
 function %d(i64) -> i64 {

cranelift/filetests/filetests/isa/riscv64/extend-op.clif

@@ -34,7 +34,7 @@ block0(v0: i64):
 }
 
 ; block0:
-;   mv a1,zero
+;   li a1,0
 ;   ret
 
 function %i128_sextend_i64(i64) -> i128 {
@@ -56,7 +56,7 @@ block0(v0: i32):
 
 ; block0:
 ;   uext.w a0,a0
-;   mv a1,zero
+;   li a1,0
 ;   ret
 
 function %i128_sextend_i32(i32) -> i128 {
@@ -79,7 +79,7 @@ block0(v0: i16):
 
 ; block0:
 ;   uext.h a0,a0
-;   mv a1,zero
+;   li a1,0
 ;   ret
 
 function %i128_sextend_i16(i16) -> i128 {
@@ -102,7 +102,7 @@ block0(v0: i8):
 
 ; block0:
 ;   uext.b a0,a0
-;   mv a1,zero
+;   li a1,0
 ;   ret
 
 function %i128_sextend_i8(i8) -> i128 {

cranelift/filetests/filetests/runtests/riscv64_issue_4996.clif

@@ -0,0 +1,24 @@
+test interpret
+test run
+set enable_llvm_abi_extensions=true
+target riscv64
+
+; This is a regression test for https://github.com/bytecodealliance/wasmtime/issues/4996.
+function %issue4996() -> i128, i64 system_v {
+    block0:
+        v5 = bconst.b1 false
+        brz v5, block3  ; v5 = false
+        jump block1
+    block1:
+        v12 = iconst.i64 0
+        v13 = uextend.i128 v12  ; v12 = 0
+        jump block5(v13)
+
+    block3:
+        v21 = iconst.i128 0
+        jump block5(v21)  ; v21 = 0
+    block5(v23: i128):
+        v29 = iconst.i64 0
+        return v23, v29  ; v29 = 0
+}
+; run: %issue4996() == [0,0]