[llvm] [LV] Create in-loop sub reductions (PR #147026)

[Sam Tebbs via llvm-commits]

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@@ -1288,6 +1308,10 @@ RecurrenceDescriptor::getReductionOpChain(PHINode *Phi, Loop *L) const {
     if (isFMulAddIntrinsic(Cur))
       return true;
 
+    // Recognize a sub reduction. It gets canonicalized to add(sub (0, ...)).
+    if (Cur->getOpcode() == Instruction::Sub && getOpcode() == Instruction::Add)
+      return true;
+
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SamTebbs33 wrote:

It isn't, thanks.

https://github.com/llvm/llvm-project/pull/147026