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Apply TargetMachine options as function attributes in IR. Needed for LTO.

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This commit is contained in:
Johan Engelen 2016-10-05 12:54:43 +02:00
parent 197c81439d
commit 00dfb4d138
3 changed files with 78 additions and 12 deletions
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61
gen/functions.cpp
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@ -18,6 +18,7 @@
#include "mtype.h"
#include "statement.h"
#include "template.h"
#include "driver/cl_options.h"
#include "gen/abi.h"
#include "gen/arrays.h"
#include "gen/classes.h"
@ -42,6 +43,8 @@
#include "ir/irmodule.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/CFG.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include <iostream>
llvm::FunctionType *DtoFunctionType(Type *type, IrFuncTy &irFty, Type *thistype,
@ -419,19 +422,55 @@ void applyParamAttrsToLLFunc(TypeFunction *f, IrFuncTy &irFty,
func->setAttributes(newAttrs);
}
void applyDefaultMathAttributes(IrFunction *irFunc) {
/// Applies TargetMachine options as function attributes in the IR (options for
/// which attributes exist).
/// This is e.g. needed for LTO: it tells the linker/LTO-codegen what settings
/// to use.
/// It is also needed because "unsafe-fp-math" is not properly reset in LLVM
/// between function definitions, i.e. if a function does not define a value for
/// "unsafe-fp-math" it will be compiled using the value of the previous
/// function. Therefore, each function must explicitly define the value (clang
/// does the same). See https://llvm.org/bugs/show_bug.cgi?id=23172
void applyTargetMachineAttributes(llvm::Function &func,
const llvm::TargetMachine &target) {
const llvm::TargetOptions &TO = target.Options;
// TODO: implement commandline switches to change the default values.
// "unsafe-fp-math" is not properly reset in LLVM between function
// definitions, i.e. if a function does not define a value for
// "unsafe-fp-math" it will be compiled using the value of the previous
// function. Therefore, each function must explicitly define the value (clang
// does the same).
// See https://llvm.org/bugs/show_bug.cgi?id=23172
irFunc->func->addFnAttr("unsafe-fp-math", "false");
}
// Target CPU capabilities
func.addFnAttr("target-cpu", target.getTargetCPU());
auto featStr = target.getTargetFeatureString();
if (!featStr.empty())
func.addFnAttr("target-features", featStr);
// Floating point settings
func.addFnAttr("unsafe-fp-math", TO.UnsafeFPMath ? "true" : "false");
func.addFnAttr("less-precise-fpmad",
TO.LessPreciseFPMADOption ? "true" : "false");
func.addFnAttr("no-infs-fp-math", TO.NoInfsFPMath ? "true" : "false");
func.addFnAttr("no-nans-fp-math", TO.NoNaNsFPMath ? "true" : "false");
#if LDC_LLVM_VER < 307
func.addFnAttr("use-soft-float", TO.UseSoftFloat ? "true" : "false");
#else
switch (TO.FloatABIType) {
case llvm::FloatABI::Default:
break;
case llvm::FloatABI::Soft:
func.addFnAttr("use-soft-float", "true");
break;
case llvm::FloatABI::Hard:
func.addFnAttr("use-soft-float", "false");
break;
}
#endif
// Frame pointer elimination
func.addFnAttr("no-frame-pointer-elim",
opts::disableFpElim ? "true" : "false");
}
} // anonymous namespace
////////////////////////////////////////////////////////////////////////////////
void DtoDeclareFunction(FuncDeclaration *fdecl) {
@ -523,9 +562,9 @@ void DtoDeclareFunction(FuncDeclaration *fdecl) {
}
}
// Set default math function attributes here, such that they can be overridden
// First apply the TargetMachine attributes, such that they can be overridden
// by UDAs.
applyDefaultMathAttributes(irFunc);
applyTargetMachineAttributes(*func, *gTargetMachine);
applyFuncDeclUDAs(fdecl, irFunc);
// main