[llvm] [InstCombine] FP fold, cond ? x : -x == 0 into x == 0 #85250 (PR #85673)

[Yingwei Zheng via llvm-commits]

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@@ -7972,6 +7972,13 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
   Constant *RHSC;
   if (match(Op0, m_Instruction(LHSI)) && match(Op1, m_Constant(RHSC))) {
     switch (LHSI->getOpcode()) {
+    case Instruction::Select:
+      if ((Pred == FCmpInst::FCMP_UEQ || Pred == FCmpInst::FCMP_OEQ ||
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dtcxzyw wrote:

> I'm concerned this (half nofpclass(inf nan norm sub) %y) might cause test failures.

It is for alive2 proof, but not for tests.


https://github.com/llvm/llvm-project/pull/85673