[PATCH] D97550: [LLD][ELF][ARM] Refactor inBranchRange to use addend for PC Bias

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added inline comments.


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Comment at: lld/ELF/Arch/ARM.cpp:301
     uint64_t dst = (expr == R_PLT_PC) ? s.getPltVA() : s.getVA();
-    return !inBranchRange(type, branchAddr, dst);
+    return !inBranchRange(type, branchAddr, dst + a);
   }
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IIUC a is usually -8, so `dst+a-branchAddr` is the value to be encoded. So this simplifies understanding. `inBranchRange` can just use the regular `[-2**n, 2**n)` range instead of doing some compensation.


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Comment at: lld/ELF/Relocations.cpp:1937
+  // Compensate for the different ARM/Thumb PC bias so we can reuse more thunks.
+  int64_t keyAddend = rel.addend + getPCBias(rel.type);
 
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MaskRay wrote:
> This probably needs a test (similar to D70637) to test sharing, even if it is difficult to construct a test exercising the range limit.
Perhaps the comment can say that `keyAddend` is usually 0, even on ARM.


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  https://reviews.llvm.org/D97550/new/

https://reviews.llvm.org/D97550