Add instructions using CPU flags.

Add integer and floating comparison instructions that return CPU flags:
ifcmp, ifcmp_imm, and ffcmp.

Add conditional branch instructions that check CPU flags: brif, brff

Add instructions that check a condition in the CPU flags and return a
b1: trueif, trueff.

lib/cretonne/src/ir/instructions.rs

@@ -141,11 +141,21 @@ pub enum InstructionData {
         arg: Value,
         imm: Imm64,
     },
+    IntCond {
+        opcode: Opcode,
+        cond: IntCC,
+        arg: Value,
+    },
     FloatCompare {
         opcode: Opcode,
         cond: FloatCC,
         args: [Value; 2],
     },
+    FloatCond {
+        opcode: Opcode,
+        cond: FloatCC,
+        arg: Value,
+    },
     Jump {
         opcode: Opcode,
         destination: Ebb,
@@ -162,6 +172,18 @@ pub enum InstructionData {
         destination: Ebb,
         args: ValueList,
     },
+    BranchInt {
+        opcode: Opcode,
+        cond: IntCC,
+        destination: Ebb,
+        args: ValueList,
+    },
+    BranchFloat {
+        opcode: Opcode,
+        cond: FloatCC,
+        destination: Ebb,
+        args: ValueList,
+    },
     BranchTable {
         opcode: Opcode,
         arg: Value,