Merge pull request #614 from aofei/min-max

ssa: add support for `min` and `max` built-in functions

ssa/expr.go

@@ -383,7 +383,7 @@ var boolPredOpToLLVM = []llvm.IntPredicate{
 	token.NEQ - predOpBase: llvm.IntNE,
 }
 
-// EQL NEQ LSS LEQ GTR GEQ      == != < <= < >=
+// EQL NEQ LSS LEQ GTR GEQ      == != < <= > >=
 func isPredOp(op token.Token) bool {
 	return op >= predOpBase && op <= predOpLast
 }
@@ -392,7 +392,7 @@ func isPredOp(op token.Token) bool {
 // op can be:
 // ADD SUB MUL QUO REM          + - * / %
 // AND OR XOR SHL SHR AND_NOT   & | ^ << >> &^
-// EQL NEQ LSS LEQ GTR GEQ      == != < <= < >=
+// EQL NEQ LSS LEQ GTR GEQ      == != < <= > >=
 func (b Builder) BinOp(op token.Token, x, y Expr) Expr {
 	if debugInstr {
 		log.Printf("BinOp %d, %v, %v\n", op, x.impl, y.impl)
@@ -490,7 +490,7 @@ func (b Builder) BinOp(op token.Token, x, y Expr) Expr {
 			llop := logicOpToLLVM[op-logicOpBase]
 			return Expr{llvm.CreateBinOp(b.impl, llop, x.impl, y.impl), x.Type}
 		}
-	case isPredOp(op): // op: == != < <= < >=
+	case isPredOp(op): // op: == != < <= > >=
 		prog := b.Prog
 		tret := prog.Bool()
 		kind := x.kind
@@ -1014,6 +1014,22 @@ func (b Builder) Do(da DoAction, fn Expr, args ...Expr) (ret Expr) {
 	return
 }
 
+// compareSelect performs a series of comparisons and selections based on the
+// given comparison op. It's used to implement operations like min and max.
+//
+// The function iterates through the provided expressions, comparing each with
+// the current result using the specified comparison op. It selects the
+// appropriate value based on the comparison.
+func (b Builder) compareSelect(op token.Token, x Expr, y ...Expr) Expr {
+	ret := x
+	for _, v := range y {
+		cond := b.BinOp(op, ret, v)
+		sel := llvm.CreateSelect(b.impl, cond.impl, ret.impl, v.impl)
+		ret = Expr{sel, ret.Type}
+	}
+	return ret
+}
+
 // A Builtin represents a specific use of a built-in function, e.g. len.
 //
 // Builtins are immutable values.  Builtins do not have addresses.
@@ -1124,6 +1140,14 @@ func (b Builder) BuiltinCall(fn string, args ...Expr) (ret Expr) {
 			b.Call(b.Pkg.rtFunc("MapClear"), t, m)
 			return
 		}
+	case "min":
+		if len(args) > 0 {
+			return b.compareSelect(token.LSS, args[0], args[1:]...)
+		}
+	case "max":
+		if len(args) > 0 {
+			return b.compareSelect(token.GTR, args[0], args[1:]...)
+		}
 	}
 	panic("todo: " + fn)
 }

ssa/ssa_test.go

@@ -521,3 +521,34 @@ func TestBasicType(t *testing.T) {
 		}
 	}
 }
+
+func TestCompareSelect(t *testing.T) {
+	prog := NewProgram(nil)
+	pkg := prog.NewPackage("bar", "foo/bar")
+
+	params := types.NewTuple(
+		types.NewVar(0, nil, "a", types.Typ[types.Int]),
+		types.NewVar(0, nil, "b", types.Typ[types.Int]),
+		types.NewVar(0, nil, "c", types.Typ[types.Int]),
+	)
+	rets := types.NewTuple(types.NewVar(0, nil, "", types.Typ[types.Int]))
+	sig := types.NewSignatureType(nil, nil, nil, params, rets, false)
+	fn := pkg.NewFunc("fn", sig, InGo)
+
+	b := fn.MakeBody(1)
+	result := b.compareSelect(token.GTR, fn.Param(0), fn.Param(1), fn.Param(2))
+	b.Return(result)
+
+	assertPkg(t, pkg, `; ModuleID = 'foo/bar'
+source_filename = "foo/bar"
+
+define i64 @fn(i64 %0, i64 %1, i64 %2) {
+_llgo_0:
+  %3 = icmp sgt i64 %0, %1
+  %4 = select i1 %3, i64 %0, i64 %1
+  %5 = icmp sgt i64 %4, %2
+  %6 = select i1 %5, i64 %4, i64 %2
+  ret i64 %6
+}
+`)
+}