[all-commits] [llvm/llvm-project] d43a80: Revert "[LAA] Remove loop-invariant check added in...

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d43a80936d437d217d5a6dbbaa5fb131c27e7085
      https://github.com/llvm/llvm-project/commit/d43a80936d437d217d5a6dbbaa5fb131c27e7085
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2024-08-27 (Tue, 27 Aug 2024)

  Changed paths:
    M llvm/lib/Analysis/LoopAccessAnalysis.cpp
    M llvm/test/Analysis/LoopAccessAnalysis/depend_diff_types.ll
    M llvm/test/Analysis/LoopAccessAnalysis/non-constant-strides-backward.ll
    M llvm/test/Transforms/LoopVectorize/global_alias.ll

  Log Message:
  -----------
  Revert "[LAA] Remove loop-invariant check added in 234cc40adc61."

This reverts commit a80053322b765eec93951e21db490c55521da2d8.

The new asserts exposed an underlying issue where the expanded bounds
could wrap, causing the parts of the code to incorrectly determine that
accesses do not overlap.

Reproducer below based on @mstorsjo's test case.

opt -passes='print<access-info>'

target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"

define i32 @j(ptr %P, i32 %x, i32 %y) {
entry:
  %gep.P.4 = getelementptr inbounds nuw i8, ptr %P, i32 4
  %gep.P.8 = getelementptr inbounds nuw i8, ptr %P, i32 8
  br label %loop

loop:
  %1 = phi i32 [ %x, %entry ], [ %sel, %loop.latch ]
  %iv = phi i32 [ %y, %entry ], [ %iv.next, %loop.latch ]
  %gep.iv = getelementptr inbounds i64, ptr %gep.P.8, i32 %iv
  %l = load i32, ptr %gep.iv, align 4
  %c.1 = icmp eq i32 %l, 3
  br i1 %c.1, label %loop.latch, label %if.then

if.then:                                          ; preds = %for.body
  store i64 0, ptr %gep.iv, align 4
  %l.2 = load i32, ptr %gep.P.4
  br label %loop.latch

loop.latch:
  %sel = phi i32 [ %l.2, %if.then ], [ %1, %loop ]
  %iv.next = add nsw i32 %iv, 1
  %c.2 = icmp slt i32 %iv.next, %sel
  br i1 %c.2, label %loop, label %exit

exit:
  %res = phi i32 [ %iv.next, %loop.latch ]
  ret i32 %res
}



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