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| -rw-r--r-- | lib/Target/README.txt | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index faa351a..a7fa802 100644 --- 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. + +//===---------------------------------------------------------------------===// + |