[Delinerization] Require by offset to be zero.

[Meinersbur]

Summary

Fixes the same bug as D108885, without fixing the API.

[bmahjour]

LGTM

llvm/lib/Analysis/Delinearization.cpp

for (int i = Last; i >= 0; i--) {
     });
 
     Res = Q;
 
     // Do not record the last subscript corresponding to the size of elements in
     // the array.
     if (i == Last) {
 
-      // Bail out if the remainder is too complex.
-      if (isa<SCEVAddRecExpr>(R)) {
+      // Bail out if the byte offset is non-zero.
+      if (!R->isZero()) {
         Subscripts.clear();
         Sizes.clear();
         return;
       }
 
       continue;
     }
 

llvm/test/Analysis/Delinearization/byte_offset.ll

+; RUN: opt < %s -analyze -enable-new-pm=0 -delinearize | FileCheck %s
+; RUN: opt < %s -passes='print<delinearization>' -disable-output 2>&1 | FileCheck %s
+
+; CHECK: AccessFunction: ({0,+,%i2}<%outer.loop> + %unknown)
+; CHECK-NEXT: failed to delinearize
+
+; void foo(char A[], long i2, bool c) {
+;   for (long i = 0; ; ++i) {
+;     char *tmp = &A[i * i2];
+;     if (c)
+;       while (1)
+;          *((float*)&tmp[arg << arg]) = 0;
+;   }
+; }
+
+define void @foo(i8* %A, i64 %i2, i64 %arg, i1 %c) {
+entry:
+  br label %outer.loop
+
+outer.loop:
+  %outer.iv = phi i64 [ 0, %entry ], [ %outer.iv.next, %outer.latch ]
+  %i414 = mul nsw i64 %outer.iv, %i2
+  %tmp = getelementptr inbounds i8, i8* %A, i64 %i414
+  br i1 %c, label %inner.preheader, label %outer.latch
+
+inner.preheader:
+  %unknown = shl i64 %arg, %arg
+  %arrayidx = getelementptr inbounds i8, i8* %tmp, i64 %unknown
+  %ptr = bitcast i8* %arrayidx to float*
+  br label %inner.loop
+
+inner.loop:
+  store float 0.000000e+00, float* %ptr, align 4
+  br label %inner.loop
+
+outer.latch:
+  %outer.iv.next = add nuw nsw i64 %outer.iv, 1
+  br label %outer.loop
+}