Add ineg legalization for scalar integer types (#1385)

cranelift/filetests/filetests/isa/x86/legalize-custom.clif

@@ -90,3 +90,44 @@ block0(v0: f32, v1: f32):
     ; check: $done(v2: f32):
     ; nextln: return v2
 }
+
+function %ineg_legalized_i8() {
+block0:
+    v0 = iconst.i8 1
+    v1 = ineg v0
+    ; check: v2 = iconst.i32 1
+    ; nextln: v0 = ireduce.i8 v2
+    ; nextln: v3 = iconst.i8 0
+    ; nextln: v4 = uextend.i32 v3
+    ; nextln: v5 = uextend.i32 v0
+    ; nextln: v6 = isub v4, v5
+    ; nextln: v1 = ireduce.i8 v6
+
+    return
+}
+
+function %ineg_legalized_i16() {
+block0:
+    v0 = iconst.i16 1
+    v1 = ineg v0
+    ; check: v2 = iconst.i32 1
+    ; nextln: v0 = ireduce.i16 v2
+    ; nextln: v3 = iconst.i16 0
+    ; nextln: v4 = uextend.i32 v3
+    ; nextln: v5 = uextend.i32 v0
+    ; nextln: v6 = isub v4, v5
+    ; nextln: v1 = ireduce.i16 v6
+
+    return
+}
+
+function %ineg_legalized_i32() {
+block0:
+    v0 = iconst.i32 1
+    v1 = ineg v0
+    ; check: v0 = iconst.i32 1
+    ; nextln: v2 = iconst.i32 0
+    ; nextln: v1 = isub v2, v0
+
+    return
+}

cranelift/filetests/filetests/isa/x86/legalize-i64.clif

@@ -338,3 +338,20 @@ block0(v1: i64):
     ; nextln: v10 = bor $b1, $c2
     return v10
 }
+
+function %ineg_legalized_i64() {
+block0:
+    v0 = iconst.i64 1
+    v1 = ineg v0
+    ; check: v2 = iconst.i32 1
+    ; nextln: v3 = iconst.i32 0
+    ; nextln: v0 = iconcat v2, v3
+    ; nextln: v5 = iconst.i32 0
+    ; nextln: v6 = iconst.i32 0
+    ; nextln: v4 = iconcat v5, v6
+    ; nextln: v7, v8 = isub_ifbout v5, v2
+    ; nextln: v9 = isub_ifbin v6, v3, v8
+    ; nextln: v1 = iconcat v7, v9
+
+    return
+}

cranelift/filetests/filetests/isa/x86/legalize-ineg-x86_64.clif

@@ -0,0 +1,13 @@
+; Test the custom legalization of ineg.i64 on x86_64.
+test legalizer
+target x86_64
+
+function %ineg_legalized_i64() {
+block0:
+    v0 = iconst.i64 1
+    v1 = ineg v0
+    ; check: v0 = iconst.i64 1
+    ; nextln: v2 = iconst.i64 0
+    ; nextln: v1 = isub v2, v0
+    return
+}