[llvm] [InstCombine] Decompose more icmps into masks (PR #110836)

[Yingwei Zheng via llvm-commits]

================
@@ -5919,29 +5919,14 @@ Instruction *InstCombinerImpl::foldICmpWithTrunc(ICmpInst &ICmp) {
   // This matches patterns corresponding to tests of the signbit as well as:
   // (trunc X) u< C --> (X & -C) == 0 (are all masked-high-bits clear?)
   // (trunc X) u> C --> (X & ~C) != 0 (are any masked-high-bits set?)
-  if (auto Res = decomposeBitTestICmp(Op0, Op1, Pred, /*WithTrunc=*/true)) {
+  if (auto Res = decomposeBitTestICmp(Op0, Op1, Pred, /*WithTrunc=*/true,
+                                      /*AllowNonZeroC=*/true)) {
     Value *And = Builder.CreateAnd(Res->X, Res->Mask);
-    Constant *Zero = ConstantInt::getNullValue(Res->X->getType());
+    Constant *Zero = ConstantInt::get(Res->X->getType(), Res->C);
----------------
dtcxzyw wrote:

Should update the comment and this variable name.


https://github.com/llvm/llvm-project/pull/110836