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Teach BasicAA::getModRefInfo(CallSite, CallSite) some

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tricks based on readnone/readonly functions.

Teach memdep to look past readonly calls when analyzing
deps for a readonly call.  This allows elimination of a
few more calls from 403.gcc:

before:
     63 gvn    - Number of instructions PRE'd
 153986 gvn    - Number of instructions deleted
  50069 gvn    - Number of loads deleted

after:
     63 gvn    - Number of instructions PRE'd
 153991 gvn    - Number of instructions deleted
  50069 gvn    - Number of loads deleted

5 calls isn't much, but this adds plumbing for the next change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60794 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2008-12-09 21:19:42 +00:00
parent 3579e44bf3
commit 20d6f0982a
4 changed files with 82 additions and 22 deletions
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29
test/Transforms/GVN/readonly-calls.ll Normal file
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@@ -0,0 +1,29 @@
; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep {call.*strlen} | count 1
; Should delete the second call to strlen even though the intervening strchr call exists.
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"
define i8* @test(i8* %P, i8* %Q, i32 %x, i32 %y) nounwind readonly {
entry:
%0 = tail call i32 @strlen(i8* %P) nounwind readonly ; <i32> [#uses=2]
%1 = icmp eq i32 %0, 0 ; <i1> [#uses=1]
br i1 %1, label %bb, label %bb1
bb: ; preds = %entry
%2 = sdiv i32 %x, %y ; <i32> [#uses=1]
br label %bb1
bb1: ; preds = %bb, %entry
%x_addr.0 = phi i32 [ %2, %bb ], [ %x, %entry ] ; <i32> [#uses=1]
%3 = tail call i8* @strchr(i8* %Q, i32 97) nounwind readonly ; <i8*> [#uses=1]
%4 = tail call i32 @strlen(i8* %P) nounwind readonly ; <i32> [#uses=1]
%5 = add i32 %x_addr.0, %0 ; <i32> [#uses=1]
%.sum = sub i32 %5, %4 ; <i32> [#uses=1]
%6 = getelementptr i8* %3, i32 %.sum ; <i8*> [#uses=1]
ret i8* %6
}
declare i32 @strlen(i8*) nounwind readonly
declare i8* @strchr(i8*, i32) nounwind readonly