ValueMapping Struct Reference

Helper struct that represents how a value is mapped through different register banks. More...

#include "llvm/CodeGen/GlobalISel/RegisterBankInfo.h"

Collaboration diagram for ValueMapping:

Public Member Functions
	ValueMapping ()
	The default constructor creates an invalid (isValid() == false) instance. More...
	ValueMapping (const PartialMapping *BreakDown, unsigned NumBreakDowns)
	Initialize a ValueMapping with the given parameter. More...
const PartialMapping *	begin () const
	Iterators through the PartialMappings. More...
const PartialMapping *	end () const
bool	isValid () const
	Check if this ValueMapping is valid. More...
bool	verify (unsigned MeaningfulBitWidth) const
	Verify that this mapping makes sense for a value of MeaningfulBitWidth. More...
void	dump () const
	Print this on dbgs() stream. More...
void	print (raw_ostream &OS) const
	Print this on OS;. More...

Public Attributes
const PartialMapping *	BreakDown
	How the value is broken down between the different register banks. More...
unsigned	NumBreakDowns
	Number of partial mapping to break down this value. More...

Detailed Description

Helper struct that represents how a value is mapped through different register banks.

Note

: So far we do not have any users of the complex mappings (mappings with more than one partial mapping), but when we do, we would have needed to duplicate partial mappings. The alternative could be to use an array of pointers of partial mapping (i.e., PartialMapping **BreakDown) and duplicate the pointers instead.

E.g., Let say we have a 32-bit add and a <2 x 32-bit> vadd. We can expand the <2 x 32-bit> add into 2 x 32-bit add.

Currently the TableGen-like file would look like:

   PartialMapping[] = {
   /*32-bit add*/    {0, 32, GPR}, // Scalar entry repeated for first vec elt.
   /*2x32-bit add*/  {0, 32, GPR}, {32, 32, GPR},
   /*<2x32-bit> vadd {0, 64, VPR}
*  }; // PartialMapping duplicated.
  
*  ValueMapping[] {
*    /*plain 32-bit add*/ {&PartialMapping[0], 1},
     /*expanded vadd on 2xadd*/ {&PartialMapping[1], 2},
     /*plain <2x32-bit> vadd*/ {&PartialMapping[3], 1}
   };

With the array of pointer, we would have:

   PartialMapping[] = {
   /*32-bit add lower */ {0, 32, GPR},
   /*32-bit add upper */ {32, 32, GPR},
   /*<2x32-bit> vadd {0, 64, VPR}
*  }; // No more duplication.
  
*  BreakDowns[] = {
*  /*AddBreakDown*/ &PartialMapping[0],
   /*2xAddBreakDown*/ &PartialMapping[0], &PartialMapping[1],
   /*VAddBreakDown*/ &PartialMapping[2]
   }; // Addresses of PartialMapping duplicated (smaller).
  
   ValueMapping[] {
     /*plain 32-bit add*/ {&BreakDowns[0], 1},
     /*expanded vadd on 2xadd*/ {&BreakDowns[1], 2},
     /*plain <2x32-bit> vadd*/ {&BreakDowns[3], 1}
   };

Given that a PartialMapping is actually small, the code size impact is actually a degradation. Moreover the compile time will be hit by the additional indirection. If PartialMapping gets bigger we may reconsider.

Definition at line 859 of file RegisterBankInfo.h.

Constructor & Destructor Documentation

ValueMapping() [1/2]

ValueMapping::ValueMapping ( )

inline

The default constructor creates an invalid (isValid() == false) instance.

Definition at line 868 of file RegisterBankInfo.h.

ValueMapping() [2/2]

ValueMapping::ValueMapping ( const PartialMapping *  BreakDown, unsigned  NumBreakDowns  )

inline

Initialize a ValueMapping with the given parameter.

BreakDown needs to have a life time at least as long as this instance.

Definition at line 873 of file RegisterBankInfo.h.

Member Function Documentation

begin()

const PartialMapping* ValueMapping::begin ( ) const

inline

Iterators through the PartialMappings.

Definition at line 877 of file RegisterBankInfo.h.

dump()

void ValueMapping::dump

(

)

const

Print this on dbgs() stream.

end()

const PartialMapping* ValueMapping::end ( ) const

inline

Definition at line 878 of file RegisterBankInfo.h.

isValid()

bool ValueMapping::isValid ( ) const

inline

Check if this ValueMapping is valid.

Definition at line 881 of file RegisterBankInfo.h.

print()

void ValueMapping::print

(

raw_ostream &

OS

)

const

Print this on OS;.

verify()

bool ValueMapping::verify

(

unsigned

MeaningfulBitWidth

)

const

Verify that this mapping makes sense for a value of MeaningfulBitWidth.

Note

This method does not check anything when assertions are disabled.

Returns

True is the check was successful.

Member Data Documentation

BreakDown

const PartialMapping* ValueMapping::BreakDown

How the value is broken down between the different register banks.

Definition at line 861 of file RegisterBankInfo.h.

NumBreakDowns

unsigned ValueMapping::NumBreakDowns

Number of partial mapping to break down this value.

Definition at line 864 of file RegisterBankInfo.h.

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The documentation for this struct was generated from the following file:

• include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h