[PATCH] D153698: [InstCombine] canonicalize multi xor as cmp+select

[Allen zhong via Phabricator via llvm-commits]

Allen updated this revision to Diff 534308.
Allen added a comment.

address comment


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153698/new/

https://reviews.llvm.org/D153698

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstCombine/select-cmp.ll


Index: llvm/test/Transforms/InstCombine/select-cmp.ll
===================================================================
--- llvm/test/Transforms/InstCombine/select-cmp.ll
+++ llvm/test/Transforms/InstCombine/select-cmp.ll
@@ -345,4 +345,18 @@
   ret i1 %r
 }
 
+; https://alive2.llvm.org/ce/z/TGgJTq
+define i32 @select_icmp_xor_multi_insn(i32 noundef %a, i32 noundef %b) {
+; CHECK-LABEL: @select_icmp_xor_multi_insn(
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[XOR1:%.*]] = xor i32 [[TMP1]], -1
+; CHECK-NEXT:    ret i32 [[XOR1]]
+;
+  %tobool = icmp eq i32 %a, %b
+  %not = xor i32 %a, -1
+  %xor1 = xor i32 %not, %b
+  %cond = select i1 %tobool, i32 -1, i32 %xor1
+  ret i32 %cond
+}
+
 declare void @use(i1)
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4253,13 +4253,10 @@
     return RepOp;
 
   // We cannot replace a constant, and shouldn't even try.
-  if (isa<Constant>(Op))
-    return nullptr;
-
-  auto *I = dyn_cast<Instruction>(V);
-  if (!I || !is_contained(I->operands(), Op))
+  if (isa<Constant>(Op) || !isa<Instruction>(V))
     return nullptr;
 
+  auto *I = cast<Instruction>(V);
   // The arguments of a phi node might refer to a value from a previous
   // cycle iteration.
   if (isa<PHINode>(I))
@@ -4278,6 +4275,25 @@
   transform(I->operands(), NewOps.begin(),
             [&](Value *V) { return V == Op ? RepOp : V; });
 
+  // TODO: support more type operator
+  if (dyn_cast<BinaryOperator>(I) && !is_contained(I->operands(), Op)) {
+    for (unsigned Idx = 0, E = I->getNumOperands(); Idx < E; ++Idx) {
+      Value *NewV = I->getOperand(Idx);
+      if (!isa<BinaryOperator>(NewV))
+        continue;
+      auto *NewI = cast<BinaryOperator>(NewV);
+      if (NewI->getParent() != I->getParent())
+        continue;
+      Value *S = simplifyWithOpReplaced(NewV, Op, RepOp, Q, AllowRefinement,
+                                        MaxRecurse - 1);
+      if (!S)
+        continue;
+      Constant *Cst = dyn_cast<Constant>(S);
+      if (Cst && Cst->isNullValue())
+        NewOps[Idx] = Cst;
+    }
+  }
+
   if (!AllowRefinement) {
     // General InstSimplify functions may refine the result, e.g. by returning
     // a constant for a potentially poison value. To avoid this, implement only


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