[PATCH] D137201: [AggressiveInstCombine] Handle the insert point of the merged load correctly.

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

We found another case, that looks like this where the p3 is read out of order. We are looking into getting that fixed too.

  define i32 @loadCombine_4consecutive_badinsert(ptr %p) {
  ; LE-LABEL: @loadCombine_4consecutive_badinsert(
  ; LE-NEXT:    [[P3:%.*]] = getelementptr i8, ptr [[P:%.*]], i32 3
  ; LE-NEXT:    [[L1:%.*]] = load i32, ptr [[P]], align 1
  ; LE-NEXT:    store i8 0, ptr [[P3]], align 1
  ; LE-NEXT:    ret i32 [[L1]]
  ;
    %p1 = getelementptr i8, ptr %p, i32 1
    %p2 = getelementptr i8, ptr %p, i32 2
    %p3 = getelementptr i8, ptr %p, i32 3
    %l2 = load i8, ptr %p1
    store i8 0, ptr %p3, align 1
    %l3 = load i8, ptr %p2
    %l4 = load i8, ptr %p3
    %l1 = load i8, ptr %p
  
    %e1 = zext i8 %l1 to i32
    %e2 = zext i8 %l2 to i32
    %e3 = zext i8 %l3 to i32
    %e4 = zext i8 %l4 to i32
  
    %s2 = shl i32 %e2, 8
    %s3 = shl i32 %e3, 16
    %s4 = shl i32 %e4, 24
  
    %o1 = or i32 %e1, %s2
    %o2 = or i32 %o1, %s3
    %o3 = or i32 %o2, %s4
    ret i32 %o3
  }


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D137201/new/

https://reviews.llvm.org/D137201