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Branch analyser fixups

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This commit is contained in:
Sajid 2024-09-11 08:58:50 +06:00
parent 8d9a35a0f3
commit cbc914a43d
3 changed files with 54 additions and 28 deletions
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61
PowerAnalyse/function.cpp
View File

@ -2,6 +2,8 @@
#include <disasm.h>
#include <vector>
#include <bit>
#include <algorithm>
#include <cassert>
size_t Function::SearchBlock(size_t address) const
{
@ -39,7 +41,7 @@ Function Function::Analyze(const void* code, size_t size, size_t base)
blockStack.reserve(32);
blockStack.emplace_back();
#define RESTORE_DATA() if (!blockStack.empty()) data = (dataStart + (blocks[blockStack.back()].base / sizeof(*data))) - 1; // continue adds one
#define RESTORE_DATA() if (!blockStack.empty()) data = (dataStart + ((blocks[blockStack.back()].base + blocks[blockStack.back()].size) / sizeof(*data))) - 1; // continue adds one
// TODO: Branch fallthrough
for (; data <= dataEnd ; ++data)
@ -55,16 +57,13 @@ Function Function::Analyze(const void* code, size_t size, size_t base)
const auto op = PPC_OP(instruction);
const auto xop = PPC_XOP(instruction);
const auto isLink = instruction & 1; // call
const auto isLink = PPC_BL(instruction); // call
ppc_insn insn;
ppc::Disassemble(data, addr, insn);
if (curBlock.base == 0x28)
{
printf("");
}
// Sanity check
assert(addr == base + curBlock.base + curBlock.size);
if (curBlock.projectedSize != -1 && curBlock.size >= curBlock.projectedSize) // fallthrough
{
blockStack.pop_back();
@ -80,43 +79,46 @@ Function Function::Analyze(const void* code, size_t size, size_t base)
continue;
}
// TODO: carry projections over to false
curBlock.projectedSize = -1;
blockStack.pop_back();
// TODO: Handle absolute branches?
assert(!PPC_BA(instruction));
const auto branchDest = addr + PPC_BD(instruction);
// true/false paths
// left block: false case
// right block: true case
const auto lBase = (addr - base) + 4;
const auto rBase = insn.operands[1] - base;
const auto rBase = (addr + PPC_BD(instruction)) - base;
// these will be -1 if it's our first time seeing these blocks
auto lBlock = fn.SearchBlock(base + lBase);
if (lBlock == -1)
{
DEBUG(const auto blockBase = curBlock.base);
blocks.emplace_back(lBase, 0).projectedSize = rBase - lBase;
lBlock = blocks.size() - 1;
}
// push this first, this gets overriden by the true case as it'd be further away
if (lBlock != -1)
{
// push this first, this gets overriden by the true case as it'd be further away
DEBUG(blocks[lBlock].parent = blockBase);
blockStack.emplace_back(lBlock);
}
auto rBlock = fn.SearchBlock(base + rBase);
if (rBlock == -1)
{
blocks.emplace_back(insn.operands[1] - base, 0);
DEBUG(const auto blockBase = curBlock.base);
blocks.emplace_back(branchDest - base, 0);
rBlock = blocks.size() - 1;
DEBUG(blocks[rBlock].parent = blockBase);
blockStack.emplace_back(rBlock);
}
if (!blockStack.empty())
{
RESTORE_DATA();
}
RESTORE_DATA();
}
else if (op == PPC_OP_B || (op == PPC_OP_CTR && xop == 16) || instruction == 0) // b, blr, end padding
{
@ -127,8 +129,11 @@ Function Function::Analyze(const void* code, size_t size, size_t base)
// Keep analyzing if we have continuity
if (op == PPC_OP_B)
{
const auto branchBase = insn.operands[0] - base;
const auto branchBlock = fn.SearchBlock(insn.operands[0]);
assert(!PPC_BA(instruction));
const auto branchDest = addr + PPC_BI(instruction);
const auto branchBase = branchDest - base;
const auto branchBlock = fn.SearchBlock(branchDest);
// carry over our projection if blocks are next to each other
const auto isContinious = branchBase == curBlock.base + curBlock.size;
@ -140,25 +145,27 @@ Function Function::Analyze(const void* code, size_t size, size_t base)
if (branchBlock == -1)
{
DEBUG(const auto blockBase = curBlock.base);
blocks.emplace_back(branchBase, 0, sizeProjection);
blockStack.emplace_back(blocks.size() - 1);
DEBUG(blocks.back().parent = blockBase);
RESTORE_DATA();
continue;
}
}
}
if (!blockStack.empty())
{
RESTORE_DATA();
}
RESTORE_DATA();
}
}
}
fn.size = 0;
for (const auto& block : blocks)
{
// pick the block furthest away
fn.size = std::max(fn.size, block.base + block.size);
fn.size = std::max(size, block.base + block.size);
}
return fn;
}

9
PowerAnalyse/function.h
View File

@ -1,12 +1,19 @@
#pragma once
#include <vector>
#ifdef _DEBUG(X)
#define DEBUG(X) X
#else
#define DEBUG(X)
#endif
struct Function
{
struct Block
{
size_t base{};
size_t size{};
DEBUG(size_t parent{});
// scratch
size_t projectedSize{ static_cast<size_t>(-1) };
@ -15,7 +22,7 @@ struct Function
size_t base{};
size_t size{};
std::vector<Block> blocks{};
size_t SearchBlock(size_t address) const;
static Function Analyze(const void* code, size_t size, size_t base);
};

12
thirdparty/disasm/ppc.h vendored
View File

@ -7,6 +7,18 @@
/* A macro to extract the extended opcode from an instruction. */
#define PPC_XOP(i) (((i) >> 1) & 0x3ff)
/* A macro to extract the branch destination from a conditional instruction. */
#define PPC_BD(i) ((signed int)((((i) & 0xFFFC) ^ 0x8000) - 0x8000))
/* A macro to extract the branch destination from an immediate instruction. */
#define PPC_BI(i) ((signed int)((((i) & 0x3FFFFFC) ^ 0x2000000) - 0x2000000))
/* A macro to extract whether the branch is absolute. */
#define PPC_BA(i) (!!((i) & 2))
/* A macro to extract whether the branch is a link. */
#define PPC_BL(i) (!!((i) & 1))
#define PPC_OP_TDI 2
#define PPC_OP_TWI 3
#define PPC_OP_MULLI 7