[PATCH] D154206: [InstCombine] Fold comparison of usub.sat

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:3438
+      Value *II1 = II->getOperand(1);
+      ICmpInst::Predicate EqPred =
+          Pred == ICmpInst::ICMP_EQ ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
----------------
`EqPred` is kind of confusing (since its a non-equality pred), maybe `NewPred`?


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp:3673
+    Value *II1 = II->getOperand(1);
+    if (match(II1, m_Constant())) {
+      if (ICmpInst::compare(APInt::getZero(C.getBitWidth()), C, Pred))
----------------
`m_ImmConstant()` here as well.


================
Comment at: llvm/test/Transforms/InstCombine/icmp-usub-sat.ll:120
+
+declare i8 @llvm.usub.sat.i8(i8, i8)
----------------
nikic wrote:
> Add a multi-use and vector test.
Can you split tests to seperate patch (make series with tests as Patch1 then impl as Patch2) so we can see the diff this patch causes.


Repository:
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  https://reviews.llvm.org/D154206/new/

https://reviews.llvm.org/D154206