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gvn now hoists this load out of the hot non-call path. 

llvm-svn: 61028
This commit is contained in:
Chris Lattner 2008-12-15 06:34:48 +00:00
parent 0c68ae0603
commit 3c2c36b590
2 changed files with 54 additions and 29 deletions
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29
llvm/lib/Target/README.txt
View File

@ -1404,32 +1404,3 @@ void foo (int a, struct T b)
//===---------------------------------------------------------------------===//
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.
//===---------------------------------------------------------------------===//

54
llvm/test/Transforms/GVN/lpre-call-wrap.ll Normal file
View File

@ -0,0 +1,54 @@
; RUN: llvm-as < %s | opt -gvn -enable-load-pre | llvm-dis > %t
; RUN: %prcontext bb3.backedge: 2 < %t | grep phi
; RUN: %prcontext bb3.backedge: 2 < %t | not grep load
;
; Make sure the load in bb3.backedge is removed and moved into bb1 after the
; call. This makes the non-call case faster.
;
; This test is derived from this C++ code:
; 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; }
;
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin7"
%struct.A = type { i32, i32 }
define void @_Z12testfunctionR1A(%struct.A* %iter) {
entry:
%0 = getelementptr %struct.A* %iter, i32 0, i32 0 ; <i32*> [#uses=3]
%1 = load i32* %0, align 4 ; <i32> [#uses=2]
%2 = icmp eq i32 %1, 0 ; <i1> [#uses=1]
br i1 %2, label %return, label %bb.nph
bb.nph: ; preds = %entry
%3 = getelementptr %struct.A* %iter, i32 0, i32 1 ; <i32*> [#uses=1]
br label %bb
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]
%8 = icmp eq i32 %7, 0 ; <i1> [#uses=1]
br i1 %8, label %return, label %bb
return: ; preds = %bb3.backedge, %entry
ret void
}
declare void @_Z1gv()