[llvm] [GlobalISel] Add G_SUB for computeNumSignBits (PR #158384)
    Matt Arsenault via llvm-commits 
    llvm-commits at lists.llvm.org
       
    Tue Sep 16 06:28:40 PDT 2025
    
    
  
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@@ -1976,6 +1976,42 @@ unsigned GISelValueTracking::computeNumSignBits(Register R,
 
     break;
   }
+  case TargetOpcode::G_SUB: {
+    Register Src1 = MI.getOperand(1).getReg();
+    unsigned Src1NumSignBits =
+        computeNumSignBits(Src1, DemandedElts, Depth + 1);
+    if (Src1NumSignBits == 1)
+      return 1; // Early Out.
+
+    Register Src2 = MI.getOperand(2).getReg();
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arsenm wrote:
swap 1/2
https://github.com/llvm/llvm-project/pull/158384
    
    
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