add a note
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25876 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/README.txt b/lib/Target/PowerPC/README.txt
index e23c6e7..eccdae7 100644
--- a/lib/Target/PowerPC/README.txt
+++ b/lib/Target/PowerPC/README.txt
@@ -435,3 +435,32 @@
same operands (but backwards) exists. In this case, this wouldn't save us
anything though, because the compares still wouldn't be shared.
+===-------------------------------------------------------------------------===
+
+The legalizer should lower this:
+
+bool %test(ulong %x) {
+ %tmp = setlt ulong %x, 4294967296
+ ret bool %tmp
+}
+
+into "if x.high == 0", not:
+
+_test:
+ addi r2, r3, -1
+ cntlzw r2, r2
+ cntlzw r3, r3
+ srwi r2, r2, 5
+ srwi r3, r3, 5
+ li r4, 0
+ cmpwi cr0, r2, 0
+ bne cr0, LBB1_2 ;
+LBB1_1:
+ or r4, r3, r3
+LBB1_2:
+ cmplw cr7, r4, r3
+ mfcr r2, 1
+ rlwinm r3, r2, 29, 31, 31
+ blr
+
+noticed in 2005-05-11-Popcount-ffs-fls.c.