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

[Chris Lattner]

Changes in directory llvm/lib/Target/PowerPC:

README.txt updated: 1.34 -> 1.35
---
Log message:

a bad case for bitfield insert


---
Diffs of the changes:  (+34 -0)

 README.txt |   34 ++++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+)


Index: llvm/lib/Target/PowerPC/README.txt
diff -u llvm/lib/Target/PowerPC/README.txt:1.34 llvm/lib/Target/PowerPC/README.txt:1.35
--- llvm/lib/Target/PowerPC/README.txt:1.34	Tue Oct 25 18:50:02 2005
+++ llvm/lib/Target/PowerPC/README.txt	Thu Oct 27 19:20:45 2005
@@ -185,3 +185,37 @@
 things like this, rather than forcing llvm to generate the equivalent
 
 (shl (add bitfield, C2), C1) with some kind of mask.
+
+===-------------------------------------------------------------------------===
+
+Compile this (standard bitfield insert of a constant):
+void %test(uint* %tmp1) {
+        %tmp2 = load uint* %tmp1                ; <uint> [#uses=1]
+        %tmp5 = or uint %tmp2, 257949696                ; <uint> [#uses=1]
+        %tmp6 = and uint %tmp5, 4018143231              ; <uint> [#uses=1]
+        store uint %tmp6, uint* %tmp1
+        ret void
+}
+
+to:
+
+_test:
+        lwz r0,0(r3)
+        li r2,123
+        rlwimi r0,r2,21,3,10
+        stw r0,0(r3)
+        blr
+
+instead of:
+
+_test:
+        lis r2, -4225
+        lwz r4, 0(r3)
+        ori r2, r2, 65535
+        oris r4, r4, 3936
+        and r2, r4, r2
+        stw r2, 0(r3)
+        blr
+
+
+