[llvm] [InstCombine] Canonicalize more saturated-add variants (PR #100008)

[Rose Silicon via llvm-commits]

================
@@ -1395,6 +1395,348 @@ define i32 @uadd_sat(i32 %x, i32 %y) {
   %r = select i1 %c, i32 -1, i32 %a
   ret i32 %r
 }
+
+define i32 @uadd_sat_flipped(i32 %x) {
+; CHECK-LABEL: @uadd_sat_flipped(
+; CHECK-NEXT:    [[COND:%.*]] = call i32 @llvm.uadd.sat.i32(i32 [[X:%.*]], i32 9)
+; CHECK-NEXT:    ret i32 [[COND]]
+;
+  %cmp = icmp ugt i32 %x, -11
+  %add = add i32 %x, 9
+  %cond = select i1 %cmp, i32 -1, i32 %add
+  ret i32 %cond
+}
+
+define i32 @uadd_sat_flipped2(i32 %x) {
+; CHECK-LABEL: @uadd_sat_flipped2(
+; CHECK-NEXT:    [[COND:%.*]] = call i32 @llvm.uadd.sat.i32(i32 [[X:%.*]], i32 9)
+; CHECK-NEXT:    ret i32 [[COND]]
+;
+  %cmp = icmp ugt i32 %x, -10
+  %add = add i32 %x, 9
+  %cond = select i1 %cmp, i32 -1, i32 %add
+  ret i32 %cond
+}
+
+define i32 @uadd_sat_flipped3(i32 %x) {
+; CHECK-LABEL: @uadd_sat_flipped3(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i32 [[X:%.*]], -8
+; CHECK-NEXT:    [[ADD:%.*]] = add nuw i32 [[X]], 9
+; CHECK-NEXT:    [[COND:%.*]] = select i1 [[CMP]], i32 -1, i32 [[ADD]]
+; CHECK-NEXT:    ret i32 [[COND]]
+;
+  %cmp = icmp ugt i32 %x, -8
+  %add = add nuw i32 %x, 9
+  %cond = select i1 %cmp, i32 -1, i32 %add
+  ret i32 %cond
+}
+
+; Negative Test
+
+define i32 @uadd_sat_flipped3_neg_no_nuw(i32 %x) {
+; CHECK-LABEL: @uadd_sat_flipped3_neg_no_nuw(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i32 [[X:%.*]], -8
+; CHECK-NEXT:    [[ADD:%.*]] = add i32 [[X]], 9
+; CHECK-NEXT:    [[COND:%.*]] = select i1 [[CMP]], i32 -1, i32 [[ADD]]
+; CHECK-NEXT:    ret i32 [[COND]]
+;
+  %cmp = icmp ugt i32 %x, -8
+  %add = add i32 %x, 9
+  %cond = select i1 %cmp, i32 -1, i32 %add
+  ret i32 %cond
+}
+
+define i32 @uadd_sat_negative_one(i32 %x) {
+; CHECK-LABEL: @uadd_sat_negative_one(
+; CHECK-NEXT:    [[COND:%.*]] = call i32 @llvm.uadd.sat.i32(i32 [[X:%.*]], i32 1)
+; CHECK-NEXT:    ret i32 [[COND]]
+;
+  %cmp = icmp eq i32 %x, -1
+  %add = add i32 %x, 1
+  %cond = select i1 %cmp, i32 -1, i32 %add
+  ret i32 %cond
+}
+
+define i32 @uadd_sat_negative_one_poison(i32 %x) {
----------------
RSilicon wrote:

> I don't know if the scalar poison tests are interesting. The icmp with poison operand will folded to poison before the select is visited. The add with poison operand will also be folded to poison before the select is visited.

Addressed!

https://github.com/llvm/llvm-project/pull/100008