add a missed case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45141 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index 37c0a359a2b28584d8ad3c80ab776669169a388d..c942d944712581fa3695bef8429d71924daad56e 100644 (file)
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -464,3 +464,21 @@ entry:
 }
 
 //===---------------------------------------------------------------------===//
+
+This code is often produced by the SMAX expansion in SCEV:
+
+define i32 @foo(i32 %a) {
+entry:
+        %tmp15 = sub i32 99, %a         ; <i32> [#uses=2]
+        %tmp16 = icmp slt i32 %tmp15, 0         ; <i1> [#uses=1]
+        %smax = select i1 %tmp16, i32 0, i32 %tmp15             ; <i32> [#uses=1]
+        %tmp12 = add i32 %smax, %a              ; <i32> [#uses=1]
+        %tmp13 = add i32 %tmp12, 1              ; <i32> [#uses=1]
+        ret i32 %tmp13
+}
+
+Note that the tmp12 add can be pushed through the select operands, turning
+it into a "select %tmp16, %a, 99".  We apparently already do this in dag 
+combine because it isn't present in X86 output.
+
+//===---------------------------------------------------------------------===//