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If LSR went through a lot of trouble to put constants (e.g. the addr of a global
in a specific BB, don't undo this!). This allows us to compile CodeGen/X86/loop-hoist.ll into: _foo: xorl %eax, %eax *** movl L_Arr$non_lazy_ptr, %ecx movl 4(%esp), %edx LBB1_1: #cond_true movl %eax, (%ecx,%eax,4) incl %eax cmpl %edx, %eax jne LBB1_1 #cond_true LBB1_2: #return ret instead of: _foo: xorl %eax, %eax movl 4(%esp), %ecx LBB1_1: #cond_true *** movl L_Arr$non_lazy_ptr, %edx movl %eax, (%edx,%eax,4) incl %eax cmpl %ecx, %eax jne LBB1_1 #cond_true LBB1_2: #return ret This was noticed in 464.h264ref. This doesn't usually affect PPC, but strikes X86 all the time. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30290 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -3234,6 +3234,15 @@ bool SelectionDAGISel::runOnFunction(Function &Fn) {
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if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
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MadeChange |= OptimizeGEPExpression(GEPI, TLI.getTargetData());
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} else if (CastInst *CI = dyn_cast<CastInst>(I)) {
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// If the source of the cast is a constant, then this should have
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// already been constant folded. The only reason NOT to constant fold
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// it is if something (e.g. LSR) was careful to place the constant
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// evaluation in a block other than then one that uses it (e.g. to hoist
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// the address of globals out of a loop). If this is the case, we don't
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// want to forward-subst the cast.
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if (isa<Constant>(CI->getOperand(0)))
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continue;
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// If this is a noop copy, sink it into user blocks to reduce the number
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// of virtual registers that must be created and coallesced.
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MVT::ValueType SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
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