[PATCH] D79261: [MergeFuncs] Don't merge shufflevectors with different masks

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: efriedma, vsk.
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efriedma accepted this revision.
efriedma added a comment.
This revision is now accepted and ready to land.

LGTM

I thought I caught all the places that needed new code to compare masks, but I missed this; thanks.


When the shufflevector mask operand was converted into special instruction data, the FunctionComparator was not updated to account for this. As such, MergeFuncs will happily merge shufflevectors with different masks.

This fixes https://bugs.llvm.org/show_bug.cgi?id=45773.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79261

Files:
  lib/Transforms/Utils/FunctionComparator.cpp
  test/Transforms/MergeFunc/shufflevector.ll


Index: test/Transforms/MergeFunc/shufflevector.ll
===================================================================
--- /dev/null
+++ test/Transforms/MergeFunc/shufflevector.ll
@@ -0,0 +1,40 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -mergefunc < %s | FileCheck %s
+
+define internal <2 x i32> @test1(<2 x i32> %v1, <2 x i32> %v2) {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:    [[X:%.*]] = shufflevector <2 x i32> [[V1:%.*]], <2 x i32> [[V2:%.*]], <2 x i32> <i32 0, i32 1>
+; CHECK-NEXT:    ret <2 x i32> [[X]]
+;
+  %x = shufflevector <2 x i32> %v1, <2 x i32> %v2, <2 x i32> <i32 0, i32 1>
+  ret <2 x i32> %x
+}
+
+; Same mask as test1.
+define internal <2 x i32> @test2(<2 x i32> %v1, <2 x i32> %v2) {
+  %x = shufflevector <2 x i32> %v1, <2 x i32> %v2, <2 x i32> <i32 0, i32 1>
+  ret <2 x i32> %x
+}
+
+; Different mask than test1, don't merge.
+define internal <2 x i32> @test3(<2 x i32> %v1, <2 x i32> %v2) {
+; CHECK-LABEL: @test3(
+; CHECK-NEXT:    [[X:%.*]] = shufflevector <2 x i32> [[V1:%.*]], <2 x i32> [[V2:%.*]], <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:    ret <2 x i32> [[X]]
+;
+  %x = shufflevector <2 x i32> %v1, <2 x i32> %v2, <2 x i32> <i32 1, i32 0>
+  ret <2 x i32> %x
+}
+
+define void @caller(<2 x i32> %v1, <2 x i32> %v2) {
+; CHECK-LABEL: @caller(
+; CHECK-NEXT:    [[TMP1:%.*]] = call <2 x i32> @test1(<2 x i32> [[V1:%.*]], <2 x i32> [[V2:%.*]])
+; CHECK-NEXT:    [[TMP2:%.*]] = call <2 x i32> @test1(<2 x i32> [[V1]], <2 x i32> [[V2]])
+; CHECK-NEXT:    [[TMP3:%.*]] = call <2 x i32> @test3(<2 x i32> [[V1]], <2 x i32> [[V2]])
+; CHECK-NEXT:    ret void
+;
+  call <2 x i32> @test1(<2 x i32> %v1, <2 x i32> %v2)
+  call <2 x i32> @test2(<2 x i32> %v1, <2 x i32> %v2)
+  call <2 x i32> @test3(<2 x i32> %v1, <2 x i32> %v2)
+  ret void
+}
Index: lib/Transforms/Utils/FunctionComparator.cpp
===================================================================
--- lib/Transforms/Utils/FunctionComparator.cpp
+++ lib/Transforms/Utils/FunctionComparator.cpp
@@ -656,6 +656,16 @@
     return cmpNumbers(RMWI->getSyncScopeID(),
                       cast<AtomicRMWInst>(R)->getSyncScopeID());
   }
+  if (const ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(L)) {
+    ArrayRef<int> LMask = SVI->getShuffleMask();
+    ArrayRef<int> RMask = cast<ShuffleVectorInst>(R)->getShuffleMask();
+    if (int Res = cmpNumbers(LMask.size(), RMask.size()))
+      return Res;
+    for (size_t i = 0, e = LMask.size(); i != e; ++i) {
+      if (int Res = cmpNumbers(LMask[i], RMask[i]))
+        return Res;
+    }
+  }
   if (const PHINode *PNL = dyn_cast<PHINode>(L)) {
     const PHINode *PNR = cast<PHINode>(R);
     // Ensure that in addition to the incoming values being identical


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