rat/include/Pass/Opt/Fold.h at main · hexratcc/rat · GitHub

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// peephole constant folding and algebraic simplification, applied as local
// graph rewrites in the spirit of parse-time pessimistic peepholes
//
// references:
// - C. Click and M. Paleczny, "A Simple Graph-Based Intermediate
//   Representation", ACM SIGPLAN Workshop on IRs, 1995
// - C. Click, "Combining Analyses, Combining Optimizations", PhD thesis,
//   Rice University, 1995 (peephole rewriting on the sea-of-nodes graph)

#ifndef RAT_PASS_OPT_FOLD_H
#define RAT_PASS_OPT_FOLD_H

#include "Core.h"
#include "IR/Opcode.h"
#include "Pass/Pass.h"

namespace rat {
	struct Function;
	struct Node;
	struct ConstantNode;
	struct Type;

	Node* constant(Function& fn, Type* type, I64 value);

	Node* foldBinary(Function& fn, Opcode op, Node* lhs, Node* rhs);
	Node* foldUnary(Function& fn, Opcode op, Node* operand);
	Node* foldCompare(Function& fn, Opcode op, Node* lhs, Node* rhs);
	Node* foldConvert(Function& fn, Opcode op, Node* operand, Type* destType);
	Node* foldBinaryConst(Function& fn, Opcode op, Type* ty, U32 w, I64 a, I64 b);
	Node* foldBinaryIdentity(Function& fn, Opcode op, Type* ty, U32 w, Node* lhs, Node* rhs);
	Node* foldBinaryReassoc(Function& fn, Opcode op, Type* ty, U32 w, Node* lhs, ConstantNode* cr);
	Node* foldBinaryStrength(Function& fn, Opcode op, Type* ty, U32 w, Node* lhs, Node* rhs);
	Node* foldShiftOfShift(Function& fn, Opcode op, Type* ty, U32 w, Node* lhs, Node* rhs);

	Node* simplify(Function& fn, Node* n); // dispatch to the matching fold*

	struct FoldPass : FunctionPass {
		const C8* name() const override;
		U32 runOnFunction(Function& fn) override;

		static U64 maskW(I64 v, U32 w);									 // zero-extend low w bits
		static B32 wouldSignedDivOverflow(I64 a, I64 b); // div by 0 or INT_MIN-1
		static I64 normalizeConst(I64 v, U32 w);				 // canonical w-bit representative

		static B32 isConstWithValue(Node* n, I64 want);
		static B32 isZeroConst(Node* n);
		static B32 isOneConst(Node* n);
		static B32 isAllOnesConst(Node* n, U32 w);
		static I32 pow2Log(Node* n, U32 w);
		static B32 matchVarConst(Node* n, Opcode want, Node*& base, I64& c);
	private:
		U32 foldFunction(Function& fn);
	};
} // namespace rat

#endif