[PATCH] D153963: [InstCombine] Fold add of select and zext/sext of select condition

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:1492
+  Constant *TrueC, *FalseC;
+  if ((match(RHS, m_ZExtOrSExt(m_Value(A))) &&
+       A->getType()->getScalarSizeInBits() == 1) &&
----------------
Redundant `()`.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:1496
+                          m_ImmConstant(FalseC)))) {
+    if (CondVal == A) {
+      if (isa<ZExtInst>(RHS))
----------------
In this case, we don't have to require that False is a constant, right?


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:1502
+
+    if (match(A, m_Not(m_Specific(CondVal)))) {
+      if (isa<ZExtInst>(RHS))
----------------
And in this case, True can be non-constant.


================
Comment at: llvm/test/Transforms/InstCombine/add.ll:3066
+  ret i64 %add
+}
+
----------------
Can you please add these additional tests:
 * Negative test where select and zext args are not the same.
 * Multi-use test.
 * Vector test.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D153963/new/

https://reviews.llvm.org/D153963