[llvm] 4ff45ee - [GlobalISel][KnownBits] Simplify G_CONSTANT handling (#91946)

[via llvm-commits]

Author: Pierre van Houtryve
Date: 2024-05-13T13:59:24+02:00
New Revision: 4ff45eee36f003cda18a3654df4086e69dc245b5

URL: https://github.com/llvm/llvm-project/commit/4ff45eee36f003cda18a3654df4086e69dc245b5
DIFF: https://github.com/llvm/llvm-project/commit/4ff45eee36f003cda18a3654df4086e69dc245b5.diff

LOG: [GlobalISel][KnownBits] Simplify G_CONSTANT handling (#91946)

We called getIConstantVRegVal which again queried MRI to get the VReg
def. We already have the def, so just get the CImm directly. It can't
fail.

Added: 
    

Modified: 
    llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp b/llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
index c8199a42d15c3..32d607cfd71a7 100644
--- a/llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
@@ -256,10 +256,7 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
     break;
   }
   case TargetOpcode::G_CONSTANT: {
-    auto CstVal = getIConstantVRegVal(R, MRI);
-    if (!CstVal)
-      break;
-    Known = KnownBits::makeConstant(*CstVal);
+    Known = KnownBits::makeConstant(MI.getOperand(1).getCImm()->getValue());
     break;
   }
   case TargetOpcode::G_FRAME_INDEX: {