[PATCH] D150360: [InstCombine] Optimize compares with multiple selects as operands

[Nikita Popov via Phabricator via llvm-commits]

nikic requested changes to this revision.
nikic added a comment.
This revision now requires changes to proceed.

Looks pretty reasonable.



================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:6596-6597
+    if (match(Op0, m_Select(m_Value(Cond1), m_Value(A), m_Value(B))) &&
+        match(Op1, m_Select(m_Value(Cond2), m_Value(C), m_Value(D))) &&
+        Cond1 == Cond2) {
+      // Check whether comparison of TrueValues can be simplified
----------------



================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:6600
+      if (Value *Res = simplifyICmpInst(Pred, A, C, SQ)) {
+        Builder.SetInsertPoint(&I);
+        Value *NewICMP = Builder.CreateICmp(Pred, B, D);
----------------
Setting the insertion point is unnecessary.


================
Comment at: llvm/test/Transforms/InstCombine/icmp-with-selects.ll:4
+
+define i1 @_Z3fooib(i32 noundef %param, i1 noundef zeroext %cond) {
+; CHECK-LABEL: define i1 @_Z3fooib
----------------
Drop the noundef and zeroext parameters.


================
Comment at: llvm/test/Transforms/InstCombine/icmp-with-selects.ll:77
+}
+
----------------
Add negative tests:
1. Select conditions are not the same.
2. Neither side simplifies.

Also add multi-use tests, where one/both selects have additional uses. You'll find that you need to add some one-use checks.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D150360/new/

https://reviews.llvm.org/D150360