[PowerPC] Add another test for load/store with update

We now produce the desired code as noted in the README.txt file. Remove the
README entry and add a regression test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225205 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/README.txt

@@ -31,40 +31,6 @@ Ick.
 
 ===-------------------------------------------------------------------------===
 
-Support 'update' load/store instructions.  These are cracked on the G5, but are
-still a codesize win.
-
-With preinc enabled, this:
-
-long *%test4(long *%X, long *%dest) {
-        %Y = getelementptr long* %X, int 4
-        %A = load long* %Y
-        store long %A, long* %dest
-        ret long* %Y
-}
-
-compiles to:
-
-_test4:
-        mr r2, r3
-        lwzu r5, 32(r2)
-        lwz r3, 36(r3)
-        stw r5, 0(r4)
-        stw r3, 4(r4)
-        mr r3, r2
-        blr 
-
-with -sched=list-burr, I get:
-
-_test4:
-        lwz r2, 36(r3)
-        lwzu r5, 32(r3)
-        stw r2, 4(r4)
-        stw r5, 0(r4)
-        blr 
-
-===-------------------------------------------------------------------------===
-
 We compile the hottest inner loop of viterbi to:
 
         li r6, 0

test/CodeGen/PowerPC/ld-st-upd.ll

@@ -0,0 +1,19 @@
+; RUN: llc -mcpu=pwr7 < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc-unknown-linux-gnu"
+
+; Function Attrs: nounwind
+define i32* @test4(i32* readonly %X, i32* nocapture %dest) #0 {
+  %Y = getelementptr i32* %X, i64 4
+  %A = load i32* %Y, align 4
+  store i32 %A, i32* %dest, align 4
+  ret i32* %Y
+
+; CHECK-LABEL: @test4
+; CHECK: lwzu [[REG1:[0-9]+]], 16(3)
+; CHECK: stw [[REG1]], 0(4)
+; CHECK: blr
+}
+
+attributes #0 = { nounwind }
+