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-rw-r--r--llvm/lib/Target/README.txt6
1 files changed, 6 insertions, 0 deletions
diff --git a/llvm/lib/Target/README.txt b/llvm/lib/Target/README.txt
index 86c231bf319..1f982b7f76a 100644
--- a/llvm/lib/Target/README.txt
+++ b/llvm/lib/Target/README.txt
@@ -240,4 +240,10 @@ _bar: addic r3,r3,-1
subfe r3,r3,r3
blr
+//===---------------------------------------------------------------------===//
+
+Legalize should lower ctlz like this:
+ ctlz(x) = popcnt((x-1) & ~x)
+
+on targets that have popcnt but not ctlz. itanium, what else?
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