cranelift: Rename i{min,max} to s{min,max} (#5187)

This brings these instructions with our general naming convention
of signed instructions being prefixed with `s`.

cranelift/codegen/src/isa/riscv64/inst/args.rs

@@ -1493,7 +1493,7 @@ impl AtomicOP {
     }
 
     /// like extract but sign extend the value.
-    /// suitable for imax.
+    /// suitable for smax.
     pub(crate) fn extract_sext(
         rd: WritableReg,
         offset: Reg,
@@ -1594,9 +1594,9 @@ impl IntSelectOP {
     #[inline]
     pub(crate) fn from_ir_op(op: crate::ir::Opcode) -> Self {
         match op {
-            crate::ir::Opcode::Imax => Self::Imax,
+            crate::ir::Opcode::Smax => Self::Smax,
             crate::ir::Opcode::Umax => Self::Umax,
-            crate::ir::Opcode::Imin => Self::Imin,
+            crate::ir::Opcode::Smin => Self::Smin,
             crate::ir::Opcode::Umin => Self::Umin,
             _ => unreachable!(),
         }
@@ -1604,18 +1604,18 @@ impl IntSelectOP {
     #[inline]
     pub(crate) fn op_name(self) -> &'static str {
         match self {
-            IntSelectOP::Imax => "imax",
+            IntSelectOP::Smax => "smax",
             IntSelectOP::Umax => "umax",
-            IntSelectOP::Imin => "imin",
+            IntSelectOP::Smin => "smin",
             IntSelectOP::Umin => "umin",
         }
     }
     #[inline]
     pub(crate) fn to_int_cc(self) -> IntCC {
         match self {
-            IntSelectOP::Imax => IntCC::SignedGreaterThan,
+            IntSelectOP::Smax => IntCC::SignedGreaterThan,
             IntSelectOP::Umax => IntCC::UnsignedGreaterThan,
-            IntSelectOP::Imin => IntCC::SignedLessThan,
+            IntSelectOP::Smin => IntCC::SignedLessThan,
             IntSelectOP::Umin => IntCC::UnsignedLessThan,
         }
     }

cranelift/codegen/src/isa/riscv64/inst/emit_tests.rs

@@ -2188,7 +2188,7 @@ fn riscv64_worst_case_instruction_size() {
     candidates.push(Inst::IntSelect {
         dst: vec![writable_a0(), writable_a0()],
         ty: I128,
-        op: IntSelectOP::Imax,
+        op: IntSelectOP::Smax,
         x: ValueRegs::two(x_reg(1), x_reg(2)),
         y: ValueRegs::two(x_reg(3), x_reg(4)),
     });