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Fix PR16508.

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When phis get lowered, destination copies are inserted using an iterator that is
determined once for all phis in the block, which BuildMI interprets as a request
to insert an instruction directly before the iterator. In the case of a cyclic
phi, source copies may also be inserted directly before this iterator, which can
cause source copies to be inserted before destination copies. The fix is to keep
an iterator to the last phi and then advance it while lowering each phi in order
to insert destination copies directly after the phis.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185363 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Cameron Zwarich 2013-07-01 19:42:46 +00:00
parent b5f7b0f978
commit 03fae50cfa
2 changed files with 36 additions and 4 deletions
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12
lib/CodeGen/PHIElimination.cpp
View File

@ -66,7 +66,7 @@ namespace {
///
bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB);
void LowerPHINode(MachineBasicBlock &MBB,
MachineBasicBlock::iterator AfterPHIsIt);
MachineBasicBlock::iterator LastPHIIt);
/// analyzePHINodes - Gather information about the PHI nodes in
/// here. In particular, we want to map the number of uses of a virtual
@ -185,10 +185,11 @@ bool PHIElimination::EliminatePHINodes(MachineFunction &MF,
// Get an iterator to the first instruction after the last PHI node (this may
// also be the end of the basic block).
MachineBasicBlock::iterator AfterPHIsIt = MBB.SkipPHIsAndLabels(MBB.begin());
MachineBasicBlock::iterator LastPHIIt =
prior(MBB.SkipPHIsAndLabels(MBB.begin()));
while (MBB.front().isPHI())
LowerPHINode(MBB, AfterPHIsIt);
LowerPHINode(MBB, LastPHIIt);
return true;
}
@ -218,8 +219,11 @@ static bool isSourceDefinedByImplicitDef(const MachineInstr *MPhi,
/// LowerPHINode - Lower the PHI node at the top of the specified block,
///
void PHIElimination::LowerPHINode(MachineBasicBlock &MBB,
MachineBasicBlock::iterator AfterPHIsIt) {
MachineBasicBlock::iterator LastPHIIt) {
++NumLowered;
MachineBasicBlock::iterator AfterPHIsIt = next(LastPHIIt);
// Unlink the PHI node from the basic block, but don't delete the PHI yet.
MachineInstr *MPhi = MBB.remove(MBB.begin());

28
test/CodeGen/PowerPC/2013-07-01-PHIElimBug.ll Normal file
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@ -0,0 +1,28 @@
; RUN: llc < %s -verify-machineinstrs | FileCheck %s
target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
@g_51 = external global [8 x i32], align 4
; CHECK: func_7
; Function Attrs: nounwind
define fastcc void @func_7() #0 {
entry:
%arrayidx638 = getelementptr inbounds [3 x [1 x i32]]* undef, i64 0, i64 1, i64 0
br i1 undef, label %for.cond940, label %if.end1018
for.cond940: ; preds = %for.cond940, %if.else876
%l_655.1 = phi i32* [ getelementptr inbounds ([8 x i32]* @g_51, i64 0, i64 6), %entry ], [ %l_654.0, %for.cond940 ]
%l_654.0 = phi i32* [ null, %entry ], [ %arrayidx638, %for.cond940 ]
%exitcond = icmp eq i32 undef, 20
br i1 %exitcond, label %if.end1018, label %for.cond940
if.end1018: ; preds = %for.end957, %for.end834
%l_655.3.ph33 = phi i32* [ %l_655.1, %for.cond940 ], [ getelementptr inbounds ([8 x i32]* @g_51, i64 0, i64 6), %entry ]
store i32 0, i32* %l_655.3.ph33, align 4
ret void
}
attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }