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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57557 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index faa351a51b486f20b023eb92c4fb7c03c98eff5a..a7fa80288c62a7a5a08e987c9cf09618796fd097 100644 (file)
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -891,3 +891,33 @@ vec2d foo () {
 }
 
 //===---------------------------------------------------------------------===//
+
+This C++ file:
+void g(); struct A { int n; int m; A& operator++(void) { ++n; if (n == m) g(); 
+return *this; }    A() : n(0), m(0) { } friend bool operator!=(A const& a1, 
+A const& a2) { return a1.n != a2.n; } }; void testfunction(A& iter) { A const 
+end; while (iter != end) ++iter; }
+
+Compiles down to:
+
+bb:            ; preds = %bb3.backedge, %bb.nph
+       %.rle = phi i32 [ %1, %bb.nph ], [ %7, %bb3.backedge ]          ; <i32> [#uses=1]
+       %4 = add i32 %.rle, 1           ; <i32> [#uses=2]
+       store i32 %4, i32* %0, align 4
+       %5 = load i32* %3, align 4              ; <i32> [#uses=1]
+       %6 = icmp eq i32 %4, %5         ; <i1> [#uses=1]
+       br i1 %6, label %bb1, label %bb3.backedge
+
+bb1:           ; preds = %bb
+       tail call void @_Z1gv()
+       br label %bb3.backedge
+
+bb3.backedge:          ; preds = %bb, %bb1
+       %7 = load i32* %0, align 4              ; <i32> [#uses=2]
+
+
+The %7 load is partially redundant with the store of %4 to %0, GVN's PRE 
+should remove it, but it doesn't apply to memory objects.
+
+//===---------------------------------------------------------------------===//
+