redgpu/ispc: Intel® Implicit SPMD Program Compiler

src/opt/IsCompileTimeConstant.cpp
114 строк5 KB
Dmitry Babokin
Build with LLVM16: fix ReplaceInstWithValue() calls
31 янв 2023, 10:16
31 янв 2023, 10:160ec76b3
/*
  Copyright (c) 2022-2023, Intel Corporation
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.

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      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.

    * Neither the name of Intel Corporation nor the names of its
      contributors may be used to endorse or promote products derived from
      this software without specific prior written permission.


   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "IsCompileTimeConstant.h"

namespace ispc {

char IsCompileTimeConstantPass::ID = 0;

bool IsCompileTimeConstantPass::lowerCompileTimeConstant(llvm::BasicBlock &bb) {
    DEBUG_START_BB("IsCompileTimeConstantPass");

    llvm::Function *funcs[] = {m->module->getFunction("__is_compile_time_constant_mask"),
                               m->module->getFunction("__is_compile_time_constant_uniform_int32"),
                               m->module->getFunction("__is_compile_time_constant_varying_int32")};

    bool modifiedAny = false;
restart:
    for (llvm::BasicBlock::iterator i = bb.begin(), e = bb.end(); i != e; ++i) {
        // Iterate through the instructions looking for calls to the
        // __is_compile_time_constant_*() functions
        llvm::CallInst *callInst = llvm::dyn_cast<llvm::CallInst>(&*i);
        if (callInst == NULL)
            continue;

        int j;
        int nFuncs = sizeof(funcs) / sizeof(funcs[0]);
        for (j = 0; j < nFuncs; ++j) {
            if (funcs[j] != NULL && callInst->getCalledFunction() == funcs[j])
                break;
        }
        if (j == nFuncs)
            // not a __is_compile_time_constant_* function
            continue;

        // This optimization pass can be disabled with both the (poorly
        // named) disableGatherScatterFlattening option and
        // disableMaskAllOnOptimizations.
        if (g->opt.disableGatherScatterFlattening || g->opt.disableMaskAllOnOptimizations) {
            ReplaceInstWithValueWrapper(i, LLVMFalse);
            modifiedAny = true;
            goto restart;
        }

        // Is it a constant?  Bingo, turn the call's value into a constant
        // true value.
        llvm::Value *operand = callInst->getArgOperand(0);
        if (llvm::isa<llvm::Constant>(operand)) {
            ReplaceInstWithValueWrapper(i, LLVMTrue);
            modifiedAny = true;
            goto restart;
        }

        // This pass runs multiple times during optimization.  Up until the
        // very last time, it only replaces the call with a 'true' if the
        // value is known to be constant and otherwise leaves the call
        // alone, in case further optimization passes can help resolve its
        // value.  The last time through, it eventually has to give up, and
        // replaces any remaining ones with 'false' constants.
        if (isLastTry) {
            ReplaceInstWithValueWrapper(i, LLVMFalse);
            modifiedAny = true;
            goto restart;
        }
    }

    DEBUG_END_BB("IsCompileTimeConstantPass");

    return modifiedAny;
}

bool IsCompileTimeConstantPass::runOnFunction(llvm::Function &F) {

    llvm::TimeTraceScope FuncScope("IsCompileTimeConstantPass::runOnFunction", F.getName());
    bool modifiedAny = false;
    for (llvm::BasicBlock &BB : F) {
        modifiedAny |= lowerCompileTimeConstant(BB);
    }
    return modifiedAny;
}

llvm::Pass *CreateIsCompileTimeConstantPass(bool isLastTry) { return new IsCompileTimeConstantPass(isLastTry); }

} // namespace ispc