This revision was automatically updated to reflect the committed changes.
Closed by commit rC339282: [Builtins] Implement __builtin_clrsb to be
compatible with gcc (authored by ctopper, committed by ).
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Repository:
rC Clang
https://reviews.llvm.org/D50168
bkramer accepted this revision.
bkramer added a comment.
This revision is now accepted and ready to land.
lg
https://reviews.llvm.org/D50168
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craig.topper updated this revision to Diff 159753.
craig.topper added a comment.
Use ctlz(zero_undef=false) and sub
https://reviews.llvm.org/D50168
Files:
include/clang/Basic/Builtins.def
lib/CodeGen/CGBuiltin.cpp
test/CodeGen/builtin_clrsb.c
Index: test/CodeGen/builtin_clrsb.c
spatel added a comment.
About the bit hacking: I don't think clang should be in the optimization
business. We should be able to take the most obvious/simple representation for
this builtin and reduce it as needed (either in instcombine or the backend). So
it would be better to use the version
craig.topper updated this revision to Diff 159627.
craig.topper added a comment.
Add the test case that I failed to pick up in the original diff.
https://reviews.llvm.org/D50168
Files:
include/clang/Basic/Builtins.def
lib/CodeGen/CGBuiltin.cpp
test/CodeGen/builtin_clrsb.c
Index:
bkramer added a comment.
Test case?
Comment at: lib/CodeGen/CGBuiltin.cpp:1563
+Value *Result = Builder.CreateCall(F, {Tmp, Builder.getTrue()});
+if (Result->getType() != ResultType)
+ Result = Builder.CreateIntCast(Result, ResultType, /*isSigned*/true,
craig.topper added a comment.
Ping
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craig.topper created this revision.
craig.topper added reviewers: bkramer, efriedma, spatel.
Herald added a reviewer: javed.absar.
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gcc defines an intrinsic called __builtin_clrsb which counts the number of
extra sign bits on a number. This is equivalent
