[PATCH] D77560: [SCEV] don't try to query getSCEV() for incomplete PHIs

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

Somewhat better test (although needs further manual cleanup), that produces different results with/without the fix:

  ; RUN: opt %s -loop-reduce -S | FileCheck %s
  
  target datalayout = "e-m:e-i64:64-n32:64"
  target triple = "powerpc64le-unknown-linux-gnu"
  
  %0 = type <{ float }>
  
  define void @foo([0 x %0]* %arg) {
  bb:
    %i = getelementptr inbounds [0 x %0], [0 x %0]* %arg, i64 0, i64 -1
    %i1 = bitcast %0* %i to i8*
    %i2 = getelementptr i8, i8* %i1, i64 4
    br label %bb3
  
  bb3:                                              ; preds = %bb18, %bb
    %i4 = phi i64 [ %i20, %bb18 ], [ 0, %bb ]
    %i5 = phi i64 [ %i21, %bb18 ], [ 1, %bb ]
    br label %bb6
  
  bb6:                                              ; preds = %bb3
    br i1 undef, label %bb7, label %bb8
  
  bb7:                                              ; preds = %bb17, %bb6
    br label %bb22
  
  bb8:                                              ; preds = %bb6
    br label %bb9
  
  bb9:                                              ; preds = %bb9, %bb8
    %i10 = phi i64 [ 0, %bb8 ], [ %i16, %bb9 ]
    %i11 = add i64 %i10, %i4
    %i12 = shl i64 %i11, 2
    %i13 = getelementptr i8, i8* %i2, i64 %i12
    %i14 = bitcast i8* %i13 to float*
    %i15 = bitcast float* %i14 to <4 x float>*
    store <4 x float> undef, <4 x float>* %i15, align 4
    %i16 = add i64 %i10, 32
    br i1 true, label %bb17, label %bb9
  
  bb17:                                             ; preds = %bb9
    br i1 undef, label %bb18, label %bb7
  
  bb18:                                             ; preds = %bb17
    %i19 = add i64 undef, %i4
    %i20 = add i64 %i19, %i5
    %i21 = add nuw nsw i64 %i5, 1
    br label %bb3
  
  bb22:                                             ; preds = %bb22, %bb7
    %i23 = phi i64 [ %i26, %bb22 ], [ undef, %bb7 ]
    %i24 = add nsw i64 %i23, %i4
    %i25 = getelementptr %0, %0* %i, i64 %i24, i32 0
    store float undef, float* %i25, align 4
    %i26 = add nuw nsw i64 %i23, 1
    br label %bb22
  }

I would think `getSCEV()` should be returning `nullptr` if it is asked about an instruction that is currently being created, but i don't know.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77560/new/

https://reviews.llvm.org/D77560