[PATCH] D135957: [AArch64][SeperateConstOffsetFromGEP] Prevent pass from splitting GEP if an index has more than one use

[Zain Jaffal via Phabricator via llvm-commits]

zjaffal updated this revision to Diff 469296.
zjaffal added a comment.
Herald added subscribers: pcwang-thead, frasercrmck, luismarques, apazos, sameer.abuasal, s.egerton, Jim, jocewei, PkmX, the_o, brucehoult, MartinMosbeck, rogfer01, edward-jones, zzheng, MaskRay, jrtc27, niosHD, sabuasal, simoncook, johnrusso, rbar, asb.

Fix test case and modify riscv test


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D135957/new/

https://reviews.llvm.org/D135957

Files:
  llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
  llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll
  llvm/test/Transforms/SeparateConstOffsetFromGEP/RISCV/split-gep.ll


Index: llvm/test/Transforms/SeparateConstOffsetFromGEP/RISCV/split-gep.ll
===================================================================
--- llvm/test/Transforms/SeparateConstOffsetFromGEP/RISCV/split-gep.ll
+++ llvm/test/Transforms/SeparateConstOffsetFromGEP/RISCV/split-gep.ll
@@ -11,13 +11,13 @@
 ; CHECK-LABEL: @test1(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[I:%.*]], 5
-; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr i64, i64* [[ARRAY:%.*]], i64 [[I]]
-; CHECK-NEXT:    [[GEP4:%.*]] = getelementptr inbounds i64, i64* [[TMP0]], i64 5
-; CHECK-NEXT:    store i64 [[J:%.*]], i64* [[GEP4]], align 4
-; CHECK-NEXT:    [[GEP26:%.*]] = getelementptr inbounds i64, i64* [[TMP0]], i64 6
-; CHECK-NEXT:    store i64 [[J]], i64* [[GEP26]], align 4
-; CHECK-NEXT:    [[GEP38:%.*]] = getelementptr inbounds i64, i64* [[TMP0]], i64 35
-; CHECK-NEXT:    store i64 [[ADD]], i64* [[GEP38]], align 4
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds i64, i64* [[ARRAY:%.*]], i64 [[ADD]]
+; CHECK-NEXT:    store i64 [[J:%.*]], i64* [[GEP]], align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr i64, i64* [[ARRAY]], i64 [[I]]
+; CHECK-NEXT:    [[GEP22:%.*]] = getelementptr inbounds i64, i64* [[TMP0]], i64 6
+; CHECK-NEXT:    store i64 [[J]], i64* [[GEP22]], align 4
+; CHECK-NEXT:    [[GEP34:%.*]] = getelementptr inbounds i64, i64* [[TMP0]], i64 35
+; CHECK-NEXT:    store i64 [[ADD]], i64* [[GEP34]], align 4
 ; CHECK-NEXT:    ret i64 undef
 ;
 entry:
Index: llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll
===================================================================
--- llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll
+++ llvm/test/CodeGen/AArch64/aarch64-loop-gep-opt.ll
@@ -48,3 +48,29 @@
   br label %do.body.i.backedge
 }
 
+
+define i64 @test_loop2(i64* %arg, i64* %save, i64 %tmp1) {
+bb:
+; CHECK-LABEL: bb:
+; CHECK %tmp1 = load i64, i64* null, align 8
+; CHECK %tmp22 = add nsw i64 %tmp1, -1
+; CHECK-NOT %uglygep = getelementptr i8, i8* %0, i64 %1
+; CHECK-NOT %uglygep2 = getelementptr i8, i8* %uglygep, i64 -8
+
+  %tmp22 = add nsw i64 %tmp1, -1
+  %tmp23 = getelementptr inbounds i64, i64* %arg, i64 %tmp22
+  %tmp24 = load i64, i64* %tmp23, align 2
+  br label %bb25
+
+bb25:                                             ; preds = %bb25, %bb18
+  %tmp26 = phi i64 [ 1, %bb ], [ 0, %bb25 ]
+  %tmp29 = icmp eq i64 0, %tmp24
+  %tmp30 = select i1 %tmp29, i64 0, i64 %tmp26
+  store i64 %tmp30, i64* %save
+  %tmp31 = icmp eq i64 0, %tmp22
+  br i1 %tmp31, label %bb32, label %bb25
+
+bb32:                                             ; preds = %bb25
+  ret i64 0
+
+}
\ No newline at end of file
Index: llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
+++ llvm/lib/Transforms/Scalar/SeparateConstOffsetFromGEP.cpp
@@ -1003,6 +1003,15 @@
   // one. If LowerGEP is enabled, a structure index is accumulated in the
   // constant offset. LowerToSingleIndexGEPs or lowerToArithmetics will later
   // handle the constant offset and won't need a new structure index.
+
+  // If GEP only has one index and it is used by non-gep instructions,
+  // it is not benificial to do the split.
+  if (GEP->getNumOperands() == 2) {
+    Value *Idx = GEP->getOperand(1);
+    if (!llvm::all_of(Idx->users(),
+                      [](const User *U) { return isa<GetElementPtrInst>(U); }))
+      return false;
+  }
   gep_type_iterator GTI = gep_type_begin(*GEP);
   for (unsigned I = 1, E = GEP->getNumOperands(); I != E; ++I, ++GTI) {
     if (GTI.isSequential()) {


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