[codegen] add intcc conditions for reading carry flag

Add conditions to IntCC for checking the carry flag (Carry, NotCarry).

Fixes: https://github.com/CraneStation/cranelift/issues/980

cranelift/codegen/src/isa/arm32/mod.rs

@@ -126,6 +126,14 @@ impl TargetIsa for Isa {
     fn emit_function_to_memory(&self, func: &ir::Function, sink: &mut MemoryCodeSink) {
         emit_function(func, binemit::emit_inst, sink, self)
     }
+
+    fn unsigned_add_overflow_condition(&self) -> ir::condcodes::IntCC {
+        ir::condcodes::IntCC::UnsignedLessThan
+    }
+
+    fn unsigned_sub_overflow_condition(&self) -> ir::condcodes::IntCC {
+        ir::condcodes::IntCC::UnsignedGreaterThanOrEqual
+    }
 }
 
 impl fmt::Display for Isa {

cranelift/codegen/src/isa/arm64/mod.rs

@@ -114,6 +114,14 @@ impl TargetIsa for Isa {
     fn emit_function_to_memory(&self, func: &ir::Function, sink: &mut MemoryCodeSink) {
         emit_function(func, binemit::emit_inst, sink, self)
     }
+
+    fn unsigned_add_overflow_condition(&self) -> ir::condcodes::IntCC {
+        ir::condcodes::IntCC::UnsignedLessThan
+    }
+
+    fn unsigned_sub_overflow_condition(&self) -> ir::condcodes::IntCC {
+        ir::condcodes::IntCC::UnsignedGreaterThanOrEqual
+    }
 }
 
 impl fmt::Display for Isa {

cranelift/codegen/src/isa/mod.rs

@@ -371,4 +371,10 @@ pub trait TargetIsa: fmt::Display + Sync {
 
     /// Emit a whole function into memory.
     fn emit_function_to_memory(&self, func: &ir::Function, sink: &mut binemit::MemoryCodeSink);
+
+    /// IntCC condition for Unsigned Addition Overflow (Carry).
+    fn unsigned_add_overflow_condition(&self) -> ir::condcodes::IntCC;
+
+    /// IntCC condition for Unsigned Subtraction Overflow (Borrow/Carry).
+    fn unsigned_sub_overflow_condition(&self) -> ir::condcodes::IntCC;
 }

cranelift/codegen/src/isa/riscv/mod.rs

@@ -121,6 +121,14 @@ impl TargetIsa for Isa {
     fn emit_function_to_memory(&self, func: &ir::Function, sink: &mut MemoryCodeSink) {
         emit_function(func, binemit::emit_inst, sink, self)
     }
+
+    fn unsigned_add_overflow_condition(&self) -> ir::condcodes::IntCC {
+        unimplemented!()
+    }
+
+    fn unsigned_sub_overflow_condition(&self) -> ir::condcodes::IntCC {
+        unimplemented!()
+    }
 }
 
 #[cfg(test)]

cranelift/codegen/src/isa/x86/mod.rs

@@ -142,6 +142,14 @@ impl TargetIsa for Isa {
         let _tt = timing::prologue_epilogue();
         abi::prologue_epilogue(func, self)
     }
+
+    fn unsigned_add_overflow_condition(&self) -> ir::condcodes::IntCC {
+        ir::condcodes::IntCC::UnsignedLessThan
+    }
+
+    fn unsigned_sub_overflow_condition(&self) -> ir::condcodes::IntCC {
+        ir::condcodes::IntCC::UnsignedLessThan
+    }
 }
 
 impl fmt::Display for Isa {