[PATCH] D159209: [CodeGen] Fix incorrect insertion point selection for reduction nodes in ComplexDeinterleavingPass

[Igor Kirillov via Phabricator via llvm-commits]

igor.kirillov created this revision.
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When replacing ComplexDeinterleavingPass::ReductionOperation, we can do it
either from the Real or Imaginary part. The correct way is to take whichever
is later in the BasicBlock, but before the patch, we just always took the
Real part.

Fixes https://github.com/llvm/llvm-project/issues/65044


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159209

Files:
  llvm/lib/CodeGen/ComplexDeinterleavingPass.cpp
  llvm/test/CodeGen/AArch64/complex-deinterleaving-crash.ll


Index: llvm/test/CodeGen/AArch64/complex-deinterleaving-crash.ll
===================================================================
--- llvm/test/CodeGen/AArch64/complex-deinterleaving-crash.ll
+++ llvm/test/CodeGen/AArch64/complex-deinterleaving-crash.ll
@@ -1,4 +1,4 @@
-; XFAIL: *
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
 ; RUN: llc %s --mattr=+complxnum -o - | FileCheck %s
 
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-ni:1-p2:32:8:8:32-ni:2"
@@ -6,6 +6,10 @@
 
 ; Check that deinterleaving pass doesn't generate broken IR
 define void @check_deinterleave_crash() #0 {
+; CHECK-LABEL: check_deinterleave_crash:
+; CHECK:       // %bb.0: // %bb
+; CHECK-NEXT:    mov x8, xzr
+; CHECK-NEXT:    str wzr, [x8]
 bb:
   br label %bb173
 
Index: llvm/lib/CodeGen/ComplexDeinterleavingPass.cpp
===================================================================
--- llvm/lib/CodeGen/ComplexDeinterleavingPass.cpp
+++ llvm/lib/CodeGen/ComplexDeinterleavingPass.cpp
@@ -1424,7 +1424,17 @@
   // CompositeNode we should choose only one either Real or Imag instruction to
   // use as an anchor for generating complex instruction.
   auto It = RootToNode.find(RootI);
-  if (It != RootToNode.end() && It->second->Real == RootI) {
+  if (It != RootToNode.end()) {
+    auto RootNode = It->second;
+    assert(RootNode->Operation ==
+           ComplexDeinterleavingOperation::ReductionOperation);
+    // Find out which part, Real or Imag, comes later, and only if we come to
+    // the latest part, add it to OrderedRoots.
+    auto *R = cast<Instruction>(RootNode->Real);
+    auto *I = cast<Instruction>(RootNode->Imag);
+    auto *ReplacementAnchor = R->comesBefore(I) ? I : R;
+    if (ReplacementAnchor != RootI)
+      return false;
     OrderedRoots.push_back(RootI);
     return true;
   }


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