x64: Lower stack_addr, udiv, sdiv, urem, srem, umulhi, smulhi in ISLE (#4741)

Lower stack_addr, udiv, sdiv, urem, srem, umulhi, and smulhi in ISLE.

For udiv, sdiv, urem, and srem I opted to move the original lowering into an extern constructor, as the interactions with rax and rdx for the div instruction didn't seem meaningful to implement in ISLE. However, I'm happy to revisit this choice and move more of the embedding into ISLE.

cranelift/codegen/src/isa/x64/inst/mod.rs

@@ -208,23 +208,6 @@ impl Inst {
         }
     }
 
-    pub(crate) fn mul_hi(size: OperandSize, signed: bool, rhs: RegMem) -> Inst {
-        debug_assert!(size.is_one_of(&[
-            OperandSize::Size16,
-            OperandSize::Size32,
-            OperandSize::Size64
-        ]));
-        rhs.assert_regclass_is(RegClass::Int);
-        Inst::MulHi {
-            size,
-            signed,
-            src1: Gpr::new(regs::rax()).unwrap(),
-            src2: GprMem::new(rhs).unwrap(),
-            dst_lo: WritableGpr::from_reg(Gpr::new(regs::rax()).unwrap()),
-            dst_hi: WritableGpr::from_reg(Gpr::new(regs::rdx()).unwrap()),
-        }
-    }
-
     pub(crate) fn checked_div_or_rem_seq(
         kind: DivOrRemKind,
         size: OperandSize,