1 files changed, 33 insertions, 0 deletions
diff --git a/lib/Target/Alpha/README.txt b/lib/Target/Alpha/README.txt
new file mode 100644
index 0000000..2d1909a
--- /dev/null
+++ b/lib/Target/Alpha/README.txt
@@ -0,0 +1,33 @@
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+Fix Ordered/Unordered FP stuff
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+improve bytezap opertunities
+ulong %foo(ulong %y) {
+entry:
+        %tmp = and ulong %y,  65535
+        %tmp2 = shr ulong %tmp,  ubyte 3
+        ret ulong %tmp2
+}
+
+
+compiles to a 3 instruction sequence without instcombine
+        zapnot $16,3,$0
+        srl $0,3,$0
+        ret $31,($26),1
+ 
+After instcombine you get
+ulong %foo(ulong %y) {
+entry:
+        %tmp = shr ulong %y, ubyte 3            ; <ulong> [#uses=1]
+        %tmp2 = and ulong %tmp, 8191            ; <ulong> [#uses=1]
+        ret ulong %tmp2
+}
+
+which compiles to
+        lda $0,8191($31)
+        srl $16,3,$1
+        and $1,$0,$0
+        ret $31,($26),1
+