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Do not add PHIs with no users when creating LCSSA form. Patch by Andrew Clinton.

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llvm-svn: 127674
This commit is contained in:
Cameron Zwarich 2011-03-15 07:41:25 +00:00
parent e30c07ab2b
commit 7947e73536
3 changed files with 48 additions and 2 deletions
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10
lib/Transforms/Utils/LCSSA.cpp
View File

@ -207,6 +207,8 @@ bool LCSSA::ProcessInstruction(Instruction *Inst,
DomTreeNode *DomNode = DT->getNode(DomBB);
SmallVector<PHINode*, 16> AddedPHIs;
SSAUpdater SSAUpdate;
SSAUpdate.Initialize(Inst->getType(), Inst->getName());
@ -236,6 +238,8 @@ bool LCSSA::ProcessInstruction(Instruction *Inst,
&PN->getOperandUse(
PN->getOperandNumForIncomingValue(PN->getNumIncomingValues()-1)));
}
AddedPHIs.push_back(PN);
// Remember that this phi makes the value alive in this block.
SSAUpdate.AddAvailableValue(ExitBB, PN);
@ -262,6 +266,12 @@ bool LCSSA::ProcessInstruction(Instruction *Inst,
// Otherwise, do full PHI insertion.
SSAUpdate.RewriteUse(*UsesToRewrite[i]);
}
// Remove PHI nodes that did not have any uses rewritten.
for (unsigned i = 0, e = AddedPHIs.size(); i != e; ++i) {
if (!AddedPHIs[i]->hasNUsesOrMore(1))
AddedPHIs[i]->eraseFromParent();
}
return true;
}

2
test/Transforms/LCSSA/2006-06-03-IncorrectIDFPhis.ll
View File

@ -1,7 +1,5 @@
; RUN: opt < %s -loop-simplify -lcssa -S | \
; RUN: grep {%%SJE.0.0.lcssa = phi .struct.SetJmpMapEntry}
; RUN: opt < %s -loop-simplify -lcssa -S | \
; RUN: grep {%%SJE.0.0.lcssa1 = phi .struct.SetJmpMapEntry}
%struct.SetJmpMapEntry = type { i8*, i32, %struct.SetJmpMapEntry* }

38
test/Transforms/LCSSA/unused-phis.ll Normal file
View File

@ -0,0 +1,38 @@
; RUN: opt < %s -lcssa -S | FileCheck %s
; CHECK: exit1:
; CHECK: .lcssa =
; CHECK: exit2:
; CHECK: .lcssa2 =
; CHECK: exit3:
; CHECK-NOT: .lcssa1 =
; Test to ensure that when there are multiple exit blocks, PHI nodes are
; only inserted by LCSSA when there is a use dominated by a given exit
; block.
declare void @printf(i32 %i)
define i32 @unused_phis() nounwind {
entry:
br label %loop
loop:
%i = phi i32 [0, %entry], [1, %then2]
br i1 undef, label %exit1, label %then1
then1:
br i1 undef, label %exit2, label %then2
then2:
br i1 undef, label %exit3, label %loop
exit1:
call void @printf(i32 %i)
ret i32 %i
exit2:
ret i32 %i
exit3:
ret i32 0
}