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b1fd3cd78f
The old PPCCTRLoops pass, like the Hexagon pass version from which it was
derived, could only handle some simple loops in canonical form. We cannot
directly adapt the new Hexagon hardware loops pass, however, because the
Hexagon pass contains a fundamental assumption that non-constant-trip-count
loops will contain a guard, and this is not always true (the result being that
incorrect negative counts can be generated). With this commit, we replace the
pass with a late IR-level pass which makes use of SE to calculate the
backedge-taken counts and safely generate the loop-count expressions (including
any necessary max() parts). This IR level pass inserts custom intrinsics that
are lowered into the desired decrement-and-branch instructions.
The most fragile part of this new implementation is that interfering uses of
the counter register must be detected on the IR level (and, on PPC, this also
includes any indirect branches in addition to function calls). Also, to make
all of this work, we need a variant of the mtctr instruction that is marked
as having side effects. Without this, machine-code level CSE, DCE, etc.
illegally transform the resulting code. Hopefully, this can be improved
in the future.
This new pass is smaller than the original (and much smaller than the new
Hexagon hardware loops pass), and can handle many additional cases correctly.
In addition, the preheader-creation code has been copied from LoopSimplify, and
after we decide on where it belongs, this code will be refactored so that it
can be explicitly shared (making this implementation even smaller).
The new test-case files ctrloop-{le,lt,ne}.ll have been adapted from tests for
the new Hexagon pass. There are a few classes of loops that this pass does not
transform (noted by FIXMEs in the files), but these deficiencies can be
addressed within the SE infrastructure (thus helping many other passes as well).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181927 91177308-0d34-0410-b5e6-96231b3b80d8
92 lines
3.0 KiB
C++
92 lines
3.0 KiB
C++
//===-- PPC.h - Top-level interface for PowerPC Target ----------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains the entry points for global functions defined in the LLVM
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// PowerPC back-end.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TARGET_POWERPC_H
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#define LLVM_TARGET_POWERPC_H
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#include "MCTargetDesc/PPCMCTargetDesc.h"
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#include <string>
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// GCC #defines PPC on Linux but we use it as our namespace name
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#undef PPC
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namespace llvm {
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class PPCTargetMachine;
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class FunctionPass;
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class ImmutablePass;
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class JITCodeEmitter;
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class MachineInstr;
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class AsmPrinter;
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class MCInst;
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FunctionPass *createPPCCTRLoops(PPCTargetMachine &TM);
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FunctionPass *createPPCEarlyReturnPass();
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FunctionPass *createPPCBranchSelectionPass();
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FunctionPass *createPPCISelDag(PPCTargetMachine &TM);
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FunctionPass *createPPCJITCodeEmitterPass(PPCTargetMachine &TM,
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JITCodeEmitter &MCE);
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void LowerPPCMachineInstrToMCInst(const MachineInstr *MI, MCInst &OutMI,
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AsmPrinter &AP, bool isDarwin);
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/// \brief Creates an PPC-specific Target Transformation Info pass.
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ImmutablePass *createPPCTargetTransformInfoPass(const PPCTargetMachine *TM);
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namespace PPCII {
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/// Target Operand Flag enum.
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enum TOF {
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//===------------------------------------------------------------------===//
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// PPC Specific MachineOperand flags.
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MO_NO_FLAG,
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/// MO_DARWIN_STUB - On a symbol operand "FOO", this indicates that the
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/// reference is actually to the "FOO$stub" symbol. This is used for calls
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/// and jumps to external functions on Tiger and earlier.
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MO_DARWIN_STUB = 1,
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/// MO_PIC_FLAG - If this bit is set, the symbol reference is relative to
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/// the function's picbase, e.g. lo16(symbol-picbase).
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MO_PIC_FLAG = 2,
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/// MO_NLP_FLAG - If this bit is set, the symbol reference is actually to
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/// the non_lazy_ptr for the global, e.g. lo16(symbol$non_lazy_ptr-picbase).
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MO_NLP_FLAG = 4,
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/// MO_NLP_HIDDEN_FLAG - If this bit is set, the symbol reference is to a
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/// symbol with hidden visibility. This causes a different kind of
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/// non-lazy-pointer to be generated.
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MO_NLP_HIDDEN_FLAG = 8,
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/// The next are not flags but distinct values.
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MO_ACCESS_MASK = 0xf0,
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/// MO_LO16, MO_HA16 - lo16(symbol) and ha16(symbol)
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MO_LO16 = 1 << 4,
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MO_HA16 = 2 << 4,
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MO_TPREL16_HA = 3 << 4,
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MO_TPREL16_LO = 4 << 4,
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/// These values identify relocations on immediates folded
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/// into memory operations.
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MO_DTPREL16_LO = 5 << 4,
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MO_TLSLD16_LO = 6 << 4,
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MO_TOC16_LO = 7 << 4
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};
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} // end namespace PPCII
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} // end namespace llvm;
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#endif
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