[PATCH] D86843: [EarlyCSE] Equivalent SELECTs should hash equally

[Bryan Chan via Phabricator via llvm-commits]

bryanpkc updated this revision to Diff 288862.
bryanpkc added a comment.

Fixed linter warning.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D86843/new/

https://reviews.llvm.org/D86843

Files:
  llvm/lib/Transforms/Scalar/EarlyCSE.cpp
  llvm/test/Transforms/EarlyCSE/commute.ll


Index: llvm/test/Transforms/EarlyCSE/commute.ll
===================================================================
--- llvm/test/Transforms/EarlyCSE/commute.ll
+++ llvm/test/Transforms/EarlyCSE/commute.ll
@@ -684,6 +684,25 @@
   ret i32 %r
 }
 
+; This test is a reproducer for a bug involving inverted min/max selects
+; hashing differently but comparing as equal.  It exhibits such a pair of
+; values, and we run this test with -earlycse-debug-hash which would catch
+; the disagreement and fail if it regressed.
+define i32 @inverted_max(i32 %i) {
+; CHECK-LABEL: @inverted_max(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i32 0, [[I:%.*]]
+; CHECK-NEXT:    [[M1:%.*]] = select i1 [[CMP]], i32 [[I]], i32 0
+; CHECK-NEXT:    [[CMPINV:%.*]] = icmp sgt i32 0, [[I:%.*]]
+; CHECK-NEXT:    [[M2:%.*]] = select i1 [[CMPINV]], i32 0, i32 [[I]]
+; CHECK-NEXT:    [[R:%.*]] = add i32 [[M1]], [[M2]]
+; CHECK-NEXT:    ret i32 [[R]]
+  %cmp = icmp sle i32 0, %i
+  %m1 = select i1 %cmp, i32 %i, i32 0
+  %cmpinv = icmp sgt i32 0, %i
+  %m2 = select i1 %cmpinv, i32 0, i32 %i
+  %r = add i32 %m1, %m2
+  ret i32 %r
+}
 
 ; This test is a reproducer for a bug involving inverted min/max selects
 ; hashing differently but comparing as equal.  It exhibits such a pair of
Index: llvm/lib/Transforms/Scalar/EarlyCSE.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/EarlyCSE.cpp
+++ llvm/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -191,6 +191,19 @@
     Pred = ICmpInst::getSwappedPredicate(Pred);
   }
 
+  // Check for inverted variants of min/max by swapping operands.
+  switch (Pred) {
+  case CmpInst::ICMP_ULE:
+  case CmpInst::ICMP_UGE:
+  case CmpInst::ICMP_SLE:
+  case CmpInst::ICMP_SGE:
+    Pred = CmpInst::getInversePredicate(Pred);
+    std::swap(A, B);
+    break;
+  default:
+    break;
+  }
+
   switch (Pred) {
   case CmpInst::ICMP_UGT: Flavor = SPF_UMAX; break;
   case CmpInst::ICMP_ULT: Flavor = SPF_UMIN; break;


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