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

[Nikita Popov via llvm-commits]

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@@ -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) {
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nikic wrote:

It doesn't look like this was done. There are still 9 tests with scalar poison.

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