[PATCH] D130103: [InstCombine] Add mul with negated power of 2 constant to canEvaluateShifted.

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp:691
+  case Instruction::Mul: {
+    auto *Neg = BinaryOperator::CreateNeg(I->getOperand(0));
+    IC.InsertNewInstWith(Neg, *I);
----------------
Can we assert !isLeftShift and/or this is a mul with negated-pow2-constant?


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp:692
+    auto *Neg = BinaryOperator::CreateNeg(I->getOperand(0));
+    IC.InsertNewInstWith(Neg, *I);
+    unsigned TypeWidth = I->getType()->getScalarSizeInBits();
----------------
Is there a difference between using IC.Builder vs. manually inserting?


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Comment at: llvm/test/Transforms/InstCombine/shift.ll:1844
 
 define i64 @lshr_mul_negpow2_2(i64 %x) {
 ; CHECK-LABEL: @lshr_mul_negpow2_2(
----------------
Do we have a negative test with an extra use of the mul?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D130103/new/

https://reviews.llvm.org/D130103