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Allow constants of different types to share constant pool entries
if they have compatible encodings. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85359 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -581,6 +581,47 @@ MachineConstantPool::~MachineConstantPool() {
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delete Constants[i].Val.MachineCPVal;
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}
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/// CanShareConstantPoolEntry - Test whether the given two constants
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/// can be allocated the same constant pool entry.
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static bool CanShareConstantPoolEntry(Constant *A, Constant *B,
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const TargetData *TD) {
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// Handle the trivial case quickly.
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if (A == B) return true;
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// If they have the same type but weren't the same constant, quickly
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// reject them.
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if (A->getType() == B->getType()) return false;
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// For now, only support constants with the same size.
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if (TD->getTypeStoreSize(A->getType()) != TD->getTypeStoreSize(B->getType()))
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return false;
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// If a floating-point value and an integer value have the same encoding,
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// they can share a constant-pool entry.
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if (ConstantFP *AFP = dyn_cast<ConstantFP>(A))
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if (ConstantInt *BI = dyn_cast<ConstantInt>(B))
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return AFP->getValueAPF().bitcastToAPInt() == BI->getValue();
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if (ConstantFP *BFP = dyn_cast<ConstantFP>(B))
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if (ConstantInt *AI = dyn_cast<ConstantInt>(A))
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return BFP->getValueAPF().bitcastToAPInt() == AI->getValue();
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// Two vectors can share an entry if each pair of corresponding
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// elements could.
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if (ConstantVector *AV = dyn_cast<ConstantVector>(A))
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if (ConstantVector *BV = dyn_cast<ConstantVector>(B)) {
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if (AV->getType()->getNumElements() != BV->getType()->getNumElements())
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return false;
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for (unsigned i = 0, e = AV->getType()->getNumElements(); i != e; ++i)
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if (!CanShareConstantPoolEntry(AV->getOperand(i), BV->getOperand(i), TD))
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return false;
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return true;
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}
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// TODO: Handle other cases.
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return false;
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}
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/// getConstantPoolIndex - Create a new entry in the constant pool or return
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/// an existing one. User must specify the log2 of the minimum required
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/// alignment for the object.
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@ -594,9 +635,12 @@ unsigned MachineConstantPool::getConstantPoolIndex(Constant *C,
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//
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// FIXME, this could be made much more efficient for large constant pools.
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for (unsigned i = 0, e = Constants.size(); i != e; ++i)
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if (Constants[i].Val.ConstVal == C &&
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(Constants[i].getAlignment() & (Alignment - 1)) == 0)
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if (!Constants[i].isMachineConstantPoolEntry() &&
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CanShareConstantPoolEntry(Constants[i].Val.ConstVal, C, TD)) {
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if ((unsigned)Constants[i].getAlignment() < Alignment)
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Constants[i].Alignment = Alignment;
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return i;
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}
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Constants.push_back(MachineConstantPoolEntry(C, Alignment));
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return Constants.size()-1;
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19
test/CodeGen/X86/constant-pool-sharing.ll
Normal file
19
test/CodeGen/X86/constant-pool-sharing.ll
Normal file
@ -0,0 +1,19 @@
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; RUN: llc < %s -march=x86-64 | FileCheck %s
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; llc should share constant pool entries between this integer vector
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; and this floating-point vector since they have the same encoding.
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; CHECK: LCPI1_0(%rip), %xmm0
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; CHECK: movaps %xmm0, (%rdi)
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; CHECK: movaps %xmm0, (%rsi)
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define void @foo(<4 x i32>* %p, <4 x float>* %q, i1 %t) nounwind {
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entry:
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br label %loop
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loop:
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store <4 x i32><i32 1073741824, i32 1073741824, i32 1073741824, i32 1073741824>, <4 x i32>* %p
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store <4 x float><float 2.0, float 2.0, float 2.0, float 2.0>, <4 x float>* %q
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br i1 %t, label %loop, label %ret
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ret:
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ret void
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}
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