[llvm] [ConstraintElim] Simplify cmp after uadd.sat/usub.sat (PR #135603)

[Nikita Popov via llvm-commits]

================
@@ -0,0 +1,36 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=constraint-elimination -S %s | FileCheck %s
+
+declare i64 @llvm.uadd.sat.i64(i64, i64)
+declare i64 @llvm.usub.sat.i64(i64, i64)
+
+define i1 @uadd_sat_uge(i64 %a, i64 %b) {
+; CHECK-LABEL: define i1 @uadd_sat_uge(
+; CHECK-SAME: i64 [[A:%.*]], i64 [[B:%.*]]) {
+; CHECK-NEXT:    [[PRECOND:%.*]] = icmp ugt i64 [[A]], [[B]]
+; CHECK-NEXT:    call void @llvm.assume(i1 [[PRECOND]])
+; CHECK-NEXT:    [[ADD_SAT:%.*]] = call i64 @llvm.uadd.sat.i64(i64 [[A]], i64 1)
+; CHECK-NEXT:    ret i1 true
+;
+  %precond = icmp ugt i64 %a, %b
+  call void @llvm.assume(i1 %precond)
+  %add.sat = call i64 @llvm.uadd.sat.i64(i64 %a, i64 1)
+  %cmp = icmp ugt i64 %add.sat, %b
+  ret i1 %cmp
+}
+
+
+define i1 @usub_sat_ule(i64 %a, i64 %b) {
----------------
nikic wrote:

Add negative test that it's not ule the RHS?

https://github.com/llvm/llvm-project/pull/135603