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Change constants in BHive conversion script #39

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merged 2 commits into from
Feb 3, 2024
Merged

Change constants in BHive conversion script #39

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270305f
Change constants in BHive conversion script
boomanaiden154 Jan 27, 2024
9a63686
Add comment explaining constants
boomanaiden154 Feb 3, 2024
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19 changes: 16 additions & 3 deletions gematria/datasets/convert_bhive_to_llvm_exegesis_input.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -29,8 +29,13 @@
#include "gematria/llvm/llvm_architecture_support.h"
#include "gematria/utils/string.h"

constexpr uint64_t kInitialRegVal = 0x10000;
constexpr uint64_t kInitialMemVal = 0x7FFFFFFF;
// Use the constants from the BHive paper for setting initial register and
// memory values. These constants are set to a high enough value to avoid
// underflow and accesses within the first page, but low enough to avoid
// exceeding the virtual address space ceiling in most cases.
constexpr uint64_t kInitialRegVal = 0x12345600;
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constexpr uint64_t kInitialMemVal = 0x12345600;
constexpr unsigned kInitialMemValBitWidth = 64;
constexpr std::string_view kRegDefPrefix = "# LLVM-EXEGESIS-DEFREG ";
constexpr std::string_view kMemDefPrefix = "# LLVM-EXEGESIS-MEM-DEF ";
constexpr std::string_view kMemMapPrefix = "# LLVM-EXEGESIS-MEM-MAP ";
Expand Down Expand Up @@ -64,6 +69,14 @@ int main(int argc, char* argv[]) {
gematria::ConvertHexToString(kInitialRegVal);
std::string initial_mem_val_str =
gematria::ConvertHexToString(kInitialMemVal);
// Prefix the string with zeroes as llvm-exegesis assumes the bit width
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this is unrelated?

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Slightly unrelated, but necessary to make this patch work properly. We're assuming the memory value has a width of 64 bits, but only setting the first x bits. Exegesis determines the width of the value based on how many characters are in the string, so we need to explicitly print out the leading zeros.

// of the memory value based on the number of characters in the string.
if (kInitialMemValBitWidth > initial_mem_val_str.size() * 4)
initial_mem_val_str =
std::string(
(kInitialMemValBitWidth - initial_mem_val_str.size() * 4) / 4,
'0') +
initial_mem_val_str;
std::string register_defs_lines;
const std::unique_ptr<gematria::LlvmArchitectureSupport> llvm_support =
gematria::LlvmArchitectureSupport::X86_64();
Expand Down Expand Up @@ -173,4 +186,4 @@ int main(int argc, char* argv[]) {

file_counter++;
}
}
}
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