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MDevereauMDevereau
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Constant Fold logf128 calls (#90611)
This is a second attempt to land #84501 which failed on several targets. This patch adds the HAS_IEE754_FLOAT128 define which makes the check for typedef'ing float128 more precise by checking whether __uint128_t is available and checking if the host does not use __ibm128 which is prevalent on power pc targets and replaces IEEE754 float128s.
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‎llvm/CMakeLists.txt‎

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@@ -560,6 +560,8 @@ set(LLVM_USE_STATIC_ZSTD FALSE CACHE BOOL "Use static version of zstd. Can be TR
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set(LLVM_ENABLE_CURL "OFF" CACHE STRING "Use libcurl for the HTTP client if available. Can be ON, OFF, or FORCE_ON")
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set(LLVM_HAS_LOGF128 "OFF" CACHE STRING "Use logf128 to constant fold fp128 logarithm calls. Can be ON, OFF, or FORCE_ON")
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set(LLVM_ENABLE_HTTPLIB "OFF" CACHE STRING "Use cpp-httplib HTTP server library if available. Can be ON, OFF, or FORCE_ON")
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set(LLVM_Z3_INSTALL_DIR "" CACHE STRING "Install directory of the Z3 solver.")

‎llvm/cmake/config-ix.cmake‎

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@@ -247,6 +247,17 @@ else()
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set(HAVE_LIBEDIT 0)
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endif()
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if(LLVM_HAS_LOGF128)
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include(CheckCXXSymbolExists)
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check_cxx_symbol_exists(logf128 math.h HAS_LOGF128)
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if(LLVM_HAS_LOGF128 STREQUAL FORCE_ON AND NOT HAS_LOGF128)
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message(FATAL_ERROR "Failed to configure logf128")
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endif()
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set(LLVM_HAS_LOGF128 "${HAS_LOGF128}")
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endif()
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# function checks
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check_symbol_exists(arc4random "stdlib.h" HAVE_DECL_ARC4RANDOM)
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find_package(Backtrace)

‎llvm/include/llvm/ADT/APFloat.h‎

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@@ -19,6 +19,7 @@
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/FloatingPointMode.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/float128.h"
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#include <memory>
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#define APFLOAT_DISPATCH_ON_SEMANTICS(METHOD_CALL) \
@@ -354,6 +355,9 @@ class IEEEFloat final : public APFloatBase {
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Expected<opStatus> convertFromString(StringRef, roundingMode);
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APInt bitcastToAPInt() const;
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double convertToDouble() const;
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#ifdef HAS_IEE754_FLOAT128
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float128 convertToQuad() const;
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#endif
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float convertToFloat() const;
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/// @}
@@ -1218,6 +1222,15 @@ class APFloat : public APFloatBase {
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/// shorter semantics, like IEEEsingle and others.
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double convertToDouble() const;
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/// Converts this APFloat to host float value.
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///
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/// \pre The APFloat must be built using semantics, that can be represented by
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/// the host float type without loss of precision. It can be IEEEquad and
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/// shorter semantics, like IEEEdouble and others.
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#ifdef HAS_IEE754_FLOAT128
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float128 convertToQuad() const;
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#endif
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/// Converts this APFloat to host float value.
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///
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/// \pre The APFloat must be built using semantics, that can be represented by

‎llvm/include/llvm/ADT/APInt.h‎

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@@ -17,6 +17,7 @@
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/float128.h"
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#include <cassert>
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#include <climits>
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#include <cstring>
@@ -1677,6 +1678,13 @@ class [[nodiscard]] APInt {
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/// any bit width. Exactly 64 bits will be translated.
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double bitsToDouble() const { return llvm::bit_cast<double>(getWord(0)); }
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#ifdef HAS_IEE754_FLOAT128
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float128 bitsToQuad() const {
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__uint128_t ul = ((__uint128_t)U.pVal[1] << 64) + U.pVal[0];
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return llvm::bit_cast<float128>(ul);
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}
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#endif
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/// Converts APInt bits to a float
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///
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/// The conversion does not do a translation from integer to float, it just

‎llvm/include/llvm/Config/llvm-config.h.cmake‎

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@@ -198,4 +198,7 @@
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/* Define if plugins enabled */
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#cmakedefine LLVM_ENABLE_PLUGINS
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/* Define if logf128 is available */
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#cmakedefine LLVM_HAS_LOGF128
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#endif

‎llvm/include/llvm/Support/float128.h‎

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@@ -0,0 +1,26 @@
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//===-- llvm/Support/float128.h - Compiler abstraction support --*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_FLOAT128
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#define LLVM_FLOAT128
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namespace llvm {
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#if defined(__clang__) && defined(__FLOAT128__) && \
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defined(__SIZEOF_INT128__) && !defined(__LONG_DOUBLE_IBM128__)
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#define HAS_IEE754_FLOAT128
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typedef __float128 float128;
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#elif defined(__FLOAT128__) && defined(__SIZEOF_INT128__) && \
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!defined(__LONG_DOUBLE_IBM128__) && \
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(defined(__GNUC__) || defined(__GNUG__))
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#define HAS_IEE754_FLOAT128
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typedef _Float128 float128;
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#endif
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} // namespace llvm
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#endif // LLVM_FLOAT128

‎llvm/lib/Analysis/CMakeLists.txt‎

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@@ -159,3 +159,9 @@ add_llvm_component_library(LLVMAnalysis
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Support
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TargetParser
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)
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include(CheckCXXSymbolExists)
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check_cxx_symbol_exists(logf128 math.h HAS_LOGF128)
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if(HAS_LOGF128)
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target_compile_definitions(LLVMAnalysis PRIVATE HAS_LOGF128)
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endif()

‎llvm/lib/Analysis/ConstantFolding.cpp‎

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@@ -2087,6 +2087,17 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
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if (IntrinsicID == Intrinsic::canonicalize)
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return constantFoldCanonicalize(Ty, Call, U);
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#if defined(HAS_IEE754_FLOAT128) && defined(HAS_LOGF128)
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if (Ty->isFP128Ty()) {
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switch (IntrinsicID) {
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default:
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return nullptr;
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case Intrinsic::log:
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return ConstantFP::get(Ty, logf128(Op->getValueAPF().convertToQuad()));
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}
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}
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#endif
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if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy())
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return nullptr;
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‎llvm/lib/Support/APFloat.cpp‎

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@@ -3665,6 +3665,15 @@ double IEEEFloat::convertToDouble() const {
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return api.bitsToDouble();
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}
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#ifdef HAS_IEE754_FLOAT128
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float128 IEEEFloat::convertToQuad() const {
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assert(semantics == (const llvm::fltSemantics *)&semIEEEquad &&
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"Float semantics are not IEEEquads");
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APInt api = bitcastToAPInt();
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return api.bitsToQuad();
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}
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#endif
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/// Integer bit is explicit in this format. Intel hardware (387 and later)
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/// does not support these bit patterns:
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/// exponent = all 1's, integer bit 0, significand 0 ("pseudoinfinity")
@@ -5260,6 +5269,21 @@ double APFloat::convertToDouble() const {
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return Temp.getIEEE().convertToDouble();
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}
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#ifdef HAS_IEE754_FLOAT128
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float128 APFloat::convertToQuad() const {
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if (&getSemantics() == (const llvm::fltSemantics *)&semIEEEquad)
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return getIEEE().convertToQuad();
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assert(getSemantics().isRepresentableBy(semIEEEquad) &&
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"Float semantics is not representable by IEEEquad");
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APFloat Temp = *this;
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bool LosesInfo;
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opStatus St = Temp.convert(semIEEEquad, rmNearestTiesToEven, &LosesInfo);
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assert(!(St & opInexact) && !LosesInfo && "Unexpected imprecision");
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(void)St;
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return Temp.getIEEE().convertToQuad();
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}
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#endif
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float APFloat::convertToFloat() const {
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if (&getSemantics() == (const llvm::fltSemantics *)&semIEEEsingle)
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return getIEEE().convertToFloat();

‎llvm/test/CMakeLists.txt‎

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@@ -26,6 +26,7 @@ llvm_canonicalize_cmake_booleans(
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LLVM_TOOL_LLVM_DRIVER_BUILD
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LLVM_INCLUDE_SPIRV_TOOLS_TESTS
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LLVM_APPEND_VC_REV
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LLVM_HAS_LOGF128
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)
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configure_lit_site_cfg(

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