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Add a testcase for GCC PR 23455, which lpre handles now. Add some

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comments about why we're not getting other cases.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61032 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-12-15 07:49:24 +00:00
parent fd7eb7252f
commit 8f416f3afd
3 changed files with 50 additions and 5 deletions
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14
lib/Target/README.txt
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@ -1323,8 +1323,13 @@ for () {
}
*P = tmp;
We now hoist the reload after the call (Transforms/GVN/lpre-call-wrap.ll), but
we don't sink the store. We need partially dead store sinking.
//===---------------------------------------------------------------------===//
[PHI TRANSLATE GEPs]
GCC PR37166: Sinking of loads prevents SROA'ing the "g" struct on the stack
leading to excess stack traffic. This could be handled by GVN with some crazy
symbolic phi translation. The code we get looks like (g is on the stack):
@ -1350,10 +1355,11 @@ There are many load PRE testcases in testsuite/gcc.dg/tree-ssa/loadpre* in the
GCC testsuite. There are many pre testcases as ssa-pre-*.c
Other simple load PRE cases:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35287
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34677 (licm does this)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29789 (SPEC2K6)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23455
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35287 [LPRE crit edge splitting]
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34677 (licm does this, LPRE crit edge)
llvm-gcc t2.c -S -o - -O0 -emit-llvm | llvm-as | opt -mem2reg -simplifycfg -gvn | llvm-dis
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14705
//===---------------------------------------------------------------------===//

39
test/Transforms/GVN/lpre-call-wrap-2.ll Normal file
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@ -0,0 +1,39 @@
; RUN: llvm-as < %s | opt -gvn -enable-load-pre | llvm-dis > %t
; RUN: %prcontext bb1: 2 < %t | grep phi
; RUN: %prcontext bb1: 2 < %t | not grep load
;
; The partially redundant load in bb1 should be hoisted to "bb". This comes
; from this C code (GCC PR 23455):
; unsigned outcnt; extern void flush_outbuf(void);
; void bi_windup(unsigned char *outbuf, unsigned char bi_buf) {
; outbuf[outcnt] = bi_buf;
; if (outcnt == 16384)
; flush_outbuf();
; outbuf[outcnt] = bi_buf;
; }
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"
@outcnt = common global i32 0 ; <i32*> [#uses=3]
define void @bi_windup(i8* %outbuf, i8 zeroext %bi_buf) nounwind {
entry:
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
%0 = load i32* @outcnt, align 4 ; <i32> [#uses=1]
%1 = getelementptr i8* %outbuf, i32 %0 ; <i8*> [#uses=1]
store i8 %bi_buf, i8* %1, align 1
%2 = load i32* @outcnt, align 4 ; <i32> [#uses=1]
%3 = icmp eq i32 %2, 16384 ; <i1> [#uses=1]
br i1 %3, label %bb, label %bb1
bb: ; preds = %entry
call void @flush_outbuf() nounwind
br label %bb1
bb1: ; preds = %bb, %entry
%4 = load i32* @outcnt, align 4 ; <i32> [#uses=1]
%5 = getelementptr i8* %outbuf, i32 %4 ; <i8*> [#uses=1]
store i8 %bi_buf, i8* %5, align 1
ret void
}
declare void @flush_outbuf()

2
test/Transforms/GVN/lpre-call-wrap.ll
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@ -5,7 +5,7 @@
; 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:
; This test is derived from this C++ code (GCC PR 37810):
; void g();
; struct A {
; int n; int m;