offload demandedElts to wrapper function

Author: vortex73

llvm/lib/Analysis/ValueTracking.cpp

@@ -3926,27 +3926,24 @@ static unsigned ComputeNumSignBitsImpl(const Value *V,
       Value *Src = U->getOperand(0);
       Type *SrcTy = Src->getType();
 
+      // Skip if the source type is not an integer or integer vector type
+      // This ensures we only process integer-like types
       if (!SrcTy->isIntOrIntVectorTy())
         break;
 
       unsigned SrcBits = SrcTy->getScalarSizeInBits();
 
+      // Bitcast 'large element' scalar/vector to 'small element' vector.
       if ((SrcBits % TyBits) != 0)
         break;
 
+      // Only proceed if the destination type is a fixed-size vector
       if (isa<FixedVectorType>(Ty)) {
-        if (auto *SrcVTy = dyn_cast<FixedVectorType>(SrcTy)) {
-          APInt SrcDemandedElts =
-              APInt::getSplat(SrcVTy->getNumElements(), APInt(1, 1));
-
-          Tmp = ComputeNumSignBits(Src, SrcDemandedElts, Depth + 1, Q);
-          if (Tmp == SrcBits)
-            return TyBits;
-        } else {
-          Tmp = ComputeNumSignBits(Src, APInt(1, 1), Depth + 1, Q);
-          if (Tmp == SrcBits)
-            return TyBits;
-        }
+        // Fast case - sign splat can be simply split across the small elements.
+        // This works for both vector and scalar sources
+        Tmp = ComputeNumSignBits(Src, Depth + 1, Q);
+        if (Tmp == SrcBits)
+          return TyBits;
       }
       break;
     }

llvm/test/Transforms/InstCombine/compute-sign-bits-bitcast.ll

@@ -47,7 +47,7 @@ define <8 x i8> @test_multiple_shifts(i1 %cond) {
   ret <8 x i8> %sra2
 }
 
-; Case 4: Test with non-sign-extended source
+; (Negative) Case 4: Test with non-sign-extended source
 define <4 x i8> @test_non_sign_extended(i32 %val) {
 ; CHECK-LABEL: define <4 x i8> @test_non_sign_extended(
 ; CHECK-SAME: i32 [[VAL:%.*]]) {