Potential Missed IPSCCP Optimization Due to Range Metadata

[GINN-Imp]

For the following case, due to the attached !range !0 metadata, the value %3 is constrained to the range [0, 2). Based on control flow, when entering block %5, %3 must be 0. However, under opt -O3, LLVM only optimizes the ret instruction and does not optimize the store instruction.

By comparing the differences, we suspect this may be a missed optimization in IPSCCP?

Godbolt: https://godbolt.org/z/W41K3j8b5
alive2 proof: https://alive2.llvm.org/ce/z/6TirEj

the reduced case:

define i8 @src(ptr %0, ptr %1){
  %3 = load i8, ptr %0, align 1, !range !0
  %4 = trunc i8 %3 to i1
  br i1 %4, label %common.ret, label %5

common.ret:                                       ; preds = %5, %1
  ret i8 0

5:                                                ; preds = %1
  store i8 %3, ptr %1, align 1
  ret i8 %3
}

!0 = !{i8 0, i8 2}

opt -O3:

define noundef range(i8 0, 2) i8 @src(ptr readonly captures(none) %0, ptr writeonly captures(none) %1) local_unnamed_addr #0 {
  %3 = load i8, ptr %0, align 1, !range !0
  %4 = trunc nuw i8 %3 to i1
  br i1 %4, label %common.ret1, label %5

common.ret1:                                      ; preds = %2, %5
  ret i8 0

5:                                                ; preds = %2
  store i8 %3, ptr %1, align 1
  br label %common.ret1
}

The reduced case is derived from https://github.com/ceres-solver/ceres-solver/blob/b5b63b5b66d4075c3b7726995b704428b3985e23/internal/ceres/solver.cc#L269.