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PR9634: Don't unconditionally tell the AliasSetTracker that the PreheaderLoad

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is equivalent to any other relevant value; it isn't true in general.
If it is equivalent, the LoopPromoter will tell the AST the equivalence.
Also, delete the PreheaderLoad if it is unused.

Chris, since you were the last one to make major changes here, can you check
that this is sane?



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129049 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2011-04-07 01:35:06 +00:00
parent 8424a60fc9
commit 0e382192c1
4 changed files with 45 additions and 23 deletions
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25
lib/Transforms/Scalar/LICM.cpp
View File

@ -743,30 +743,13 @@ void LICM::PromoteAliasSet(AliasSet &AS) {
Preheader->getTerminator());
SSA.AddAvailableValue(Preheader, PreheaderLoad);
// Copy any value stored to or loaded from a must-alias of the pointer.
if (PreheaderLoad->getType()->isPointerTy()) {
Value *SomeValue;
if (LoadInst *LI = dyn_cast<LoadInst>(LoopUses[0]))
SomeValue = LI;
else
SomeValue = cast<StoreInst>(LoopUses[0])->getValueOperand();
CurAST->copyValue(SomeValue, PreheaderLoad);
}
// Rewrite all the loads in the loop and remember all the definitions from
// stores in the loop.
Promoter.run(LoopUses);
// If the preheader load is itself a pointer, we need to tell alias analysis
// about the new pointer we created in the preheader block and about any PHI
// nodes that just got inserted.
if (PreheaderLoad->getType()->isPointerTy()) {
for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
CurAST->copyValue(PreheaderLoad, NewPHIs[i]);
}
// fwew, we're done!
// If the SSAUpdater didn't use the load in the preheader, just zap it now.
if (PreheaderLoad->use_empty())
PreheaderLoad->eraseFromParent();
}

2
test/Analysis/BasicAA/store-promote.ll
View File

@ -24,7 +24,7 @@ Out: ; preds = %Loop
; The Loop block should be empty after the load/store are promoted.
; CHECK: @test1
; CHECK: load i32* @B
; CHECK: load i32* @A
; CHECK: Loop:
; CHECK-NEXT: br i1 %c, label %Out, label %Loop
; CHECK: Out:

4
test/Transforms/LICM/2007-10-01-PromoteSafeValue.ll
View File

@ -1,4 +1,4 @@
; RUN: opt < %s -licm -S | grep promoted
; RUN: opt < %s -licm -S | FileCheck %s
; Promote value if at least one use is safe
@ -15,6 +15,8 @@ cond.true: ; preds = %loop.head
store i32 40, i32* %p
br label %loop.head
; CHECK: exit:
; CHECK: store i32 20, i32* %p
exit: ; preds = %loop.head
ret i32 0
}

37
test/Transforms/LICM/2011-04-06-PromoteResultOfPromotion.ll Normal file
View File

@ -0,0 +1,37 @@
; RUN: opt < %s -tbaa -licm -S | FileCheck %s
; PR9634
@g_58 = common global i32 0, align 4
@g_116 = common global i32* null, align 8
define void @f() nounwind {
; CHECK: entry:
; CHECK: alloca [9 x i16]
; CHECK: load i32* @g_58
; CHECK: br label %for.body
entry:
%l_87.i = alloca [9 x i16], align 16
br label %for.body
for.body: ; preds = %entry, %for.inc
%inc12 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
store i32* @g_58, i32** @g_116, align 8, !tbaa !0
%tmp2 = load i32** @g_116, align 8, !tbaa !0
%tmp3 = load i32* %tmp2, !tbaa !4
%or = or i32 %tmp3, 10
store i32 %or, i32* %tmp2, !tbaa !4
%inc = add nsw i32 %inc12, 1
%cmp = icmp slt i32 %inc, 4
br i1 %cmp, label %for.body, label %for.end
for.end: ; preds = %for.inc
ret void
}
!0 = metadata !{metadata !"any pointer", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA", null}
!3 = metadata !{metadata !"short", metadata !1}
!4 = metadata !{metadata !"int", metadata !1}