[llvm-commits] CVS: llvm/lib/Target/PowerPC/README.txt

[Chris Lattner]

Changes in directory llvm/lib/Target/PowerPC:

README.txt updated: 1.52 -> 1.53
---
Log message:

add a note


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Diffs of the changes:  (+29 -0)

 README.txt |   29 +++++++++++++++++++++++++++++
 1 files changed, 29 insertions(+)


Index: llvm/lib/Target/PowerPC/README.txt
diff -u llvm/lib/Target/PowerPC/README.txt:1.52 llvm/lib/Target/PowerPC/README.txt:1.53
--- llvm/lib/Target/PowerPC/README.txt:1.52	Wed Feb  1 01:19:44 2006
+++ llvm/lib/Target/PowerPC/README.txt	Wed Feb  1 11:54:23 2006
@@ -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.