[llvm] 8148b11 - [ValueTracking] Short-circuit GEP known bits calculation (NFC)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2020-05-02T12:29:26+02:00
New Revision: 8148b116474614c176d69de8c246fc21494faf5f

URL: https://github.com/llvm/llvm-project/commit/8148b116474614c176d69de8c246fc21494faf5f
DIFF: https://github.com/llvm/llvm-project/commit/8148b116474614c176d69de8c246fc21494faf5f.diff

LOG: [ValueTracking] Short-circuit GEP known bits calculation (NFC)

Don't compute known bits of all GEP operands, if we already know
that we don't know anything.

Added: 
    

Modified: 
    llvm/lib/Analysis/ValueTracking.cpp

Removed: 
    


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diff  --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 6fbf2462046c..3d1e627e3df9 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1454,6 +1454,10 @@ static void computeKnownBitsFromOperator(const Operator *I,
 
     gep_type_iterator GTI = gep_type_begin(I);
     for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
+      // TrailZ can only become smaller, short-circuit if we hit zero.
+      if (TrailZ == 0)
+        break;
+
       Value *Index = I->getOperand(i);
       if (StructType *STy = GTI.getStructTypeOrNull()) {
         // Handle struct member offset arithmetic.