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@llvm/pr-subscribers-backend-aarch64

@llvm/pr-subscribers-llvm-globalisel

Author: Pragyansh Chaturvedi (r41k0u)

diff --git a/llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp b/llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp
index 974fc40de6222..df1b325fa5baf 100644
--- a/llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp
@@ -697,6 +697,14 @@ void GISelValueTracking::computeKnownBitsImpl(Register R, KnownBits &Known,
     }
     break;
   }
+  case TargetOpcode::G_ABS: {
+    Register SrcReg = MI.getOperand(1).getReg();
+    computeKnownBitsImpl(SrcReg, Known, DemandedElts, Depth + 1);
+    Known = Known.abs();
+    Known.Zero.setHighBits(computeNumSignBits(SrcReg, DemandedElts, Depth + 1) -
+                           1);
+    break;
+  }
   }
 
   LLVM_DEBUG(dumpResult(MI, Known, Depth));

I ran the tests and found no new regressions. I am not sure how to add tests for this (as I saw in other PRs attached to the issue). I came across update_givaluetracking_test_checks.py as the test files in other PRs seem generated. If they are required, please point me towards a test writing guide and I'll add them to this PR as well.

I ran the tests and found no new regressions. I am not sure how to add tests for this (as I saw in other PRs attached to the issue). I came across update_givaluetracking_test_checks.py as the test files in other PRs seem generated.

The output is generated, the input is not. That's a new style to directly check the output. The older style is to write the simplest code that will optimize or not based on the analysis

If they are required, please point me towards a test writing guide and I'll add them to this PR as well.

https://llvm.org/docs/TestingGuide.html#generating-assertions-in-regression-tests

You're probably best off copy-pasting one of the tests from the recent GIValueTracking commits as a starting point

Hi @davemgreen, I've added a couple of tests for this. Please lmk if more of them are needed.
I also goofed up by not creating a new branch for this PR, so once this is approved I'll rebase this against main.