[PATCH] D132252: [RISCV] Optimize x <s -1 ? x : -1. Improve x >u 1 ? x : 1.

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:4025
     // x > 1 ? x : 1 -> x > 0 ? x : 1
-    if (isOneConstant(LHS) && !isa<ConstantSDNode>(RHS) &&
-        (CCVal == ISD::SETLT || CCVal == ISD::SETULT) && RHS == TrueV &&
-        isOneConstant(FalseV)) {
+    if (isOneConstant(LHS) && (CCVal == ISD::SETLT || CCVal == ISD::SETULT) &&
+        RHS == TrueV && LHS == FalseV) {
----------------
I dropped the non-constant RHS check here because it doesn't matter for the correctness of the combine and an all constant setcc should have been DAG combined away.


================
Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:4026
+    if (isOneConstant(LHS) && (CCVal == ISD::SETLT || CCVal == ISD::SETULT) &&
+        RHS == TrueV && LHS == FalseV) {
       LHS = DAG.getConstant(0, DL, VT);
----------------
Remove the second call to isOneConstant by checking if LHS == FalseV since we already know LHS is 1. These two changes improve the similarity with the new combine introduced here.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132252/new/

https://reviews.llvm.org/D132252