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brg
InstSelectSimple.cpp: Add some comments that say what I'm going to do for calls and casts. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4832 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -363,9 +363,9 @@ ISel::visitBranchInst (BranchInst & BI)
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}
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}
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void
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ISel::visitCallInst (CallInst &CI)
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{
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/// visitCallInst - Have to push args and do a procedure call
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/// instruction, if the target address is known.
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void ISel::visitCallInst (CallInst &CI) {
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visitInstruction (CI);
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}
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@ -581,9 +581,39 @@ void ISel::visitPHINode(PHINode &PN) {
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}
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}
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/// visitCastInst - Here we have various kinds of copying with or without
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/// sign extension going on.
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void
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ISel::visitCastInst (CastInst &CI)
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{
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//> cast larger int to smaller int --> copy least significant byte/word w/ mov?
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//
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//I'm not really sure what to do with this. We could insert a pseudo-op
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//that says take the low X bits of a Y bit register, but for now we can just
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//force the value into, say, EAX, then rip out AL or AX. The advantage of
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//the former is that the register allocator could use any register it wants,
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//but for now this obviously doesn't matter. :)
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// if target type is bool
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// Emit Compare
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// Emit Set-if-not-zero
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// if size of target type == size of source type
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// Emit Mov reg(target) <- reg(source)
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// if size of target type > size of source type
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// if both types are integer types
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// if source type is signed
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// sbyte to short, ushort: Emit movsx 8->16
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// sbyte to int, uint: Emit movsx 8->32
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// short to int, uint: Emit movsx 16->32
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// else if source type is unsigned
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// ubyte to short, ushort: Emit movzx 8->16
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// ubyte to int, uint: Emit movzx 8->32
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// ushort to int, uint: Emit movzx 16->32
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// if both types are fp types
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// float to double: Emit fstp, fld (???)
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visitInstruction (CI);
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}
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@ -363,9 +363,9 @@ ISel::visitBranchInst (BranchInst & BI)
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}
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}
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void
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ISel::visitCallInst (CallInst &CI)
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{
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/// visitCallInst - Have to push args and do a procedure call
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/// instruction, if the target address is known.
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void ISel::visitCallInst (CallInst &CI) {
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visitInstruction (CI);
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}
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@ -581,9 +581,39 @@ void ISel::visitPHINode(PHINode &PN) {
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}
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}
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/// visitCastInst - Here we have various kinds of copying with or without
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/// sign extension going on.
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void
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ISel::visitCastInst (CastInst &CI)
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{
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//> cast larger int to smaller int --> copy least significant byte/word w/ mov?
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//
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//I'm not really sure what to do with this. We could insert a pseudo-op
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//that says take the low X bits of a Y bit register, but for now we can just
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//force the value into, say, EAX, then rip out AL or AX. The advantage of
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//the former is that the register allocator could use any register it wants,
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//but for now this obviously doesn't matter. :)
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// if target type is bool
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// Emit Compare
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// Emit Set-if-not-zero
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// if size of target type == size of source type
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// Emit Mov reg(target) <- reg(source)
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// if size of target type > size of source type
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// if both types are integer types
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// if source type is signed
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// sbyte to short, ushort: Emit movsx 8->16
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// sbyte to int, uint: Emit movsx 8->32
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// short to int, uint: Emit movsx 16->32
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// else if source type is unsigned
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// ubyte to short, ushort: Emit movzx 8->16
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// ubyte to int, uint: Emit movzx 8->32
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// ushort to int, uint: Emit movzx 16->32
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// if both types are fp types
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// float to double: Emit fstp, fld (???)
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visitInstruction (CI);
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}
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