[PATCH] D34515: [ARM] Materialise some boolean values to avoid a branch

[Roger Ferrer Ibanez via Phabricator via llvm-commits]

rogfer01 added inline comments.


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Comment at: lib/Target/ARM/ARMISelLowering.cpp:10015-10025
+  if (N->getOpcode() == ARMISD::SUBC) {
+    // (SUBC (ADDE 0, 0, C), 1) -> C
+    SDValue LHS = N->getOperand(0);
+    SDValue RHS = N->getOperand(1);
+    if (LHS->getOpcode() == ARMISD::ADDE &&
+        isNullConstant(LHS->getOperand(0)) &&
+        isNullConstant(LHS->getOperand(1)) && isOneConstant(RHS)) {
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I think this may make the `ADDC` combiner above redundant as `ADDC x, -1` will usually become `SUBC x, 1`. I'll try to see if I can remove the `ADDC` one.


https://reviews.llvm.org/D34515