[libc-commits] [compiler-rt] [clang] [clang-tools-extra] [llvm] [libc] [flang] [lldb] [GlobalIsel] Combine select of binops (PR #76763)

[Thorsten Schütt via libc-commits]

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@@ -6548,6 +6534,54 @@ bool CombinerHelper::tryFoldBoolSelectToLogic(GSelect *Select,
   return false;
 }
 
+bool CombinerHelper::tryFoldSelectOfBinOps(GSelect *Select,
+                                           BuildFnTy &MatchInfo) {
+  Register DstReg = Select->getReg(0);
+  Register Cond = Select->getCondReg();
+  Register False = Select->getFalseReg();
+  Register True = Select->getTrueReg();
+  LLT DstTy = MRI.getType(DstReg);
+
+  GBinOp *LHS = getOpcodeDef<GBinOp>(True, MRI);
+  GBinOp *RHS = getOpcodeDef<GBinOp>(False, MRI);
+
+  // We need two binops of the same kind on the true/false registers.
+  if (!LHS || !RHS || LHS->getOpcode() != RHS->getOpcode())
+    return false;
+
+  // Note that there are no constraints on CondTy.
+  unsigned Flags = (LHS->getFlags() & RHS->getFlags()) | Select->getFlags();
+  unsigned Opcode = LHS->getOpcode();
+
+  // Fold select(cond, binop(x, y), binop(z, y))
+  //  --> binop(select(cond, x, z), y)
+  if (LHS->getRHSReg() == RHS->getRHSReg()) {
+    MatchInfo = [=](MachineIRBuilder &B) {
+      B.setInstrAndDebugLoc(*Select);
+      auto Sel = B.buildSelect(DstTy, Cond, LHS->getLHSReg(), RHS->getLHSReg(),
+                               Select->getFlags());
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tschuett wrote:

And Flags are added to selects.

https://github.com/llvm/llvm-project/pull/76763