[PATCH] D116469: [AMDGPU] Correct the known bits calculation for MUL_I24.

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp:4629
     if (Opc == AMDGPUISD::MUL_I24) {
-      unsigned LHSValBits = 24 - LHSKnown.countMinSignBits();
-      unsigned RHSValBits = 24 - RHSKnown.countMinSignBits();
-      unsigned MaxValBits = std::min(LHSValBits + RHSValBits, 32u);
-      if (MaxValBits >= 32)
+      unsigned LHSValBits = 24 - LHSKnown.countMinSignBits() + 1;
+      unsigned RHSValBits = 24 - RHSKnown.countMinSignBits() + 1;
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Do you think it'd be confusing if we added KnownBits::getMinSignedBits() to match APInt::getMinSignedBits() ?


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Comment at: llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp:4648
       unsigned LHSValBits = 24 - LHSKnown.countMinLeadingZeros();
       unsigned RHSValBits = 24 - RHSKnown.countMinLeadingZeros();
       unsigned MaxValBits = std::min(LHSValBits + RHSValBits, 32u);
----------------
Use KnownBits::countMaxActiveBits() ?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D116469/new/

https://reviews.llvm.org/D116469