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llvm-svn: 28572
2006-05-30 21:29:15 +00:00 · 2006-05-30 21:29:15 +00:00 · a5d4587296
parent b9342afa56
commit a5d4587296
1 changed files with 19 additions and 0 deletions
--- a/llvm/lib/Target/README.txt
+++ b/llvm/lib/Target/README.txt
@ -251,3 +251,22 @@ void %test(uint* %P) {
        ret void
 }

+//===---------------------------------------------------------------------===//
+
+dag/inst combine "clz(x)>>5 -> x==0" for 32-bit x.
+
+Compile:
+
+int bar(int x)
+{
+  int t = __builtin_clz(x);
+  return -(t>>5);
+}
+
+to:
+
+_bar:   addic r3,r3,-1
+        subfe r3,r3,r3
+        blr
+
+