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emscripten
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rewrite variable analysis code. eliminate unused variables without side effects, and improve nativization logic.

This commit is contained in:
Alon Zakai 2011-12-15 15:38:26 -08:00
Родитель ad34dff9ae
Коммит 6259358a5a
9 изменённых файлов: 160 добавлений и 52 удалений
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115
src/analyzer.js
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@ -18,6 +18,7 @@ function cleanFunc(func) {
// Handy sets
var BRANCH_INVOKE = set('branch', 'invoke');
var SIDE_EFFECT_CAUSERS = set('call', 'invoke');
// Analyzer
@ -265,8 +266,6 @@ function analyzer(data) {
// Function locals
item.functions.forEach(function(func) {
dprint('vars', 'Analyzing variables in ' + func.ident);
func.variables = {};
// LLVM is SSA, so we always have a single assignment/write. We care about
@ -280,22 +279,21 @@ function analyzer(data) {
type: param.type,
origin: 'funcparam',
lineNum: func.lineNum,
uses: null
rawLinesIndex: -1
};
}
});
// Normal variables
func.lines.forEach(function(item) {
func.lines.forEach(function(item, i) {
if (item.intertype === 'assign') {
var variable = func.variables[item.ident] = {
ident: item.ident,
type: item.value.type,
origin: item.value.intertype,
lineNum: item.lineNum,
uses: item.uses
rawLinesIndex: i
};
assert(isNumber(variable.uses), 'Failed to find the # of uses of var: ' + item.ident);
if (variable.origin === 'alloca') {
variable.allocatedNum = item.value.allocatedNum;
}
@ -324,41 +322,74 @@ function analyzer(data) {
});
}
// Analyze variable uses
function analyzeVariableUses() {
dprint('vars', 'Analyzing variables for ' + func.ident + '\n');
for (vname in func.variables) {
var variable = func.variables[vname];
// Whether the value itself is used. For an int, always yes. For a pointer,
// we might never use the pointer's value - we might always just store to it /
// read from it. If so, then we can optimize away the pointer.
variable.hasValueTaken = false;
variable.pointingLevels = pointingLevels(variable.type);
variable.uses = 0;
}
// TODO: improve the analysis precision. bitcast, for example, means we take the value, but perhaps we only use it to load/store
var inNoop = 0;
func.lines.forEach(function(line) {
walkInterdata(line, function(item) {
if (item.intertype == 'noop') inNoop++;
if (!inNoop) {
if (item.ident in func.variables && item.intertype != 'assign') {
func.variables[item.ident].uses++;
if (item.intertype != 'load' && item.intertype != 'store') {
func.variables[item.ident].hasValueTaken = true;
}
}
}
}, function(item) {
if (item.intertype == 'noop') inNoop--;
});
});
}
// Filter out no longer used variables, collapsing more as we go
while (true) {
analyzeVariableUses();
var recalc = false;
keys(func.variables).forEach(function(vname) {
var variable = func.variables[vname];
if (variable.uses == 0 && variable.origin != 'funcparam') {
// Eliminate this variable if we can
var sideEffects = false;
walkInterdata(func.lines[variable.rawLinesIndex].value, function(item) {
if (item.intertype in SIDE_EFFECT_CAUSERS) sideEffects = true;
});
if (!sideEffects) {
dprint('vars', 'Eliminating ' + vname);
func.lines[variable.rawLinesIndex].intertype = func.lines[variable.rawLinesIndex].value.intertype = 'noop';
delete func.variables[vname];
recalc = true;
}
}
});
if (!recalc) break;
}
// Decision time
for (vname in func.variables) {
var variable = func.variables[vname];
// Whether the value itself is used. For an int, always yes. For a pointer,
// we might never use the pointer's value - we might always just store to it /
// read from it. If so, then we can optimize away the pointer.
variable.hasValueTaken = false;
// Whether our address was used. If not, then we do not need to bother with
// implementing this variable in a way that other functions can access it.
variable.hasAddrTaken = false;
variable.pointingLevels = pointingLevels(variable.type);
// Analysis!
if (variable.pointingLevels > 0) {
// Pointers
variable.loads = 0;
variable.stores = 0;
func.lines.forEach(function(line) {
if (line.intertype == 'store' && line.ident == vname) {
variable.stores ++;
} else if (line.intertype == 'assign' && line.value.intertype == 'load' && line.value.ident == vname) {
variable.loads ++;
}
});
variable.otherUses = variable.uses - variable.loads - variable.stores;
if (variable.otherUses > 0)
variable.hasValueTaken = true;
}
// Decision time
var pointedType = pointingLevels(variable.type) > 0 ? removePointing(variable.type) : null;
if (variable.origin == 'getelementptr') {
// Use our implementation that emulates pointers etc.
@ -369,10 +400,10 @@ function analyzer(data) {
variable.impl = VAR_EMULATED;
} else if (variable.type == 'i64*' && I64_MODE == 1) {
variable.impl = VAR_EMULATED;
} else if (MICRO_OPTS && variable.pointingLevels === 0 && !variable.hasAddrTaken) {
} else if (MICRO_OPTS && variable.pointingLevels === 0) {
// A simple int value, can be implemented as a native variable
variable.impl = VAR_NATIVE;
} else if (MICRO_OPTS && variable.origin === 'alloca' && !variable.hasAddrTaken && !variable.hasValueTaken &&
} else if (MICRO_OPTS && variable.origin === 'alloca' && !variable.hasValueTaken &&
variable.allocatedNum === 1 &&
(Runtime.isNumberType(pointedType) || Runtime.isPointerType(pointedType))) {
// A pointer to a value which is only accessible through this pointer. Basically
@ -423,7 +454,7 @@ function analyzer(data) {
item.functions.forEach(function(func) {
func.lines.forEach(function(line, i) {
if (line.intertype === 'assign' && line.value.intertype === 'load') {
var data = func.variables[line.ident]
var data = func.variables[line.ident];
if (data.type === 'i1') {
line.value.unsigned = true;
return;

3
src/compiler.js
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@ -180,9 +180,10 @@ if (FAKE_X86_FP80) {
var lines = raw.split('\n');
raw = null;
// Parse metadata
// Pre-process the LLVM assembly
Debugging.handleMetadata(lines);
PreProcessor.eliminateUnneededIntrinsics(lines);
// Do it

6
src/intertyper.js
Просмотреть файл

@ -520,7 +520,7 @@ function intertyper(data, sidePass, baseLineNums) {
});
}
} else {
if (!item.tokens[3]) throw 'Did you run llvm-dis with -show-annotations? (b)';
if (!item.tokens[3]) throw 'Did you run llvm-dis with -show-annotations? (b)'; // XXX: do we still need annotations?
if (item.tokens[3].text == 'c')
item.tokens.splice(3, 1);
if (item.tokens[3].text in PARSABLE_LLVM_FUNCTIONS) {
@ -572,13 +572,11 @@ function intertyper(data, sidePass, baseLineNums) {
substrate.addActor('Assign', {
processItem: function(item) {
var opIndex = findTokenText(item, '=');
if (!item.tokens.slice(-1)[0].item) throw 'Did you run llvm-dis with -show-annotations?';
var commentIndex = getTokenIndexByText(item.tokens, ';');
var pair = splitItem({
intertype: 'assign',
ident: toNiceIdent(combineTokens(item.tokens.slice(0, opIndex)).text),
lineNum: item.lineNum,
uses: parseInt(item.tokens[commentIndex+1].item.tokens[0].text.split('=')[1])
}, 'value');
this.forwardItem(pair.parent, 'Reintegrator');
pair.child.indent = -1;
@ -972,7 +970,7 @@ function intertyper(data, sidePass, baseLineNums) {
processItem: function(item) {
var ret = {
intertype: 'indirectbr',
pointer: parseLLVMSegment(splitTokenList(item.tokens.slice(1))[0]),
value: parseLLVMSegment(splitTokenList(item.tokens.slice(1))[0]),
type: item.tokens[1].text,
lineNum: item.lineNum
};

5
src/jsifier.js
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@ -706,6 +706,9 @@ function JSify(data, functionsOnly, givenFunctions) {
}
});
}
makeFuncLineActor('noop', function(item) {
return ';';
});
makeFuncLineActor('var', function(item) { // assigns into phis become simple vars when MICRO_OPTS
return 'var ' + item.ident + ';';
});
@ -953,7 +956,7 @@ function JSify(data, functionsOnly, givenFunctions) {
return ret + item.ident + '.f' + item.indexes[0][0].text + ' = ' + finalizeLLVMParameter(item.value) + ', ' + item.ident + ')';
});
makeFuncLineActor('indirectbr', function(item) {
return makeBranch(finalizeLLVMParameter(item.pointer), item.currLabelId, true);
return makeBranch(finalizeLLVMParameter(item.value), item.currLabelId, true);
});
makeFuncLineActor('alloca', function(item) {
if (typeof item.allocatedIndex === 'number') {

22
src/modules.js
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@ -209,6 +209,28 @@ var Debugging = {
}
};
var PreProcessor = {
eliminateUnneededIntrinsics: function(lines) {
// LLVM sometimes aggresively adds lifetime annotations, for example
//
// %0 = bitcast %"class.std::__1::__tree"** %this.addr.i to i8* ; [#uses=1 type=i8*]
// call void @llvm.lifetime.start(i64 -1, i8* %0) nounwind
// [..]
// %6 = bitcast float* %__x.addr.i to i8* ; [#uses=1 type=i8*]
// call void @llvm.lifetime.end(i64 -1, i8* %6) nounwind
//
// This greatly hurts us if we do not eliminate it ahead of time, because while we
// will correctly do nothing for the lifetime intrinsic itself, the bitcast of the
// parameter to it will prevent nativization of the variable being cast (!)
for (var i = 0; i < lines.length; i++) {
var line = lines[i];
if (/call void @llvm.lifetime.(start|end)\(i\d+ -1, i8\* %(\d+)\).*/.exec(line)) {
lines[i] = ';';
}
}
}
};
var Variables = {
globals: {}
};

6
src/parseTools.js
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@ -410,7 +410,7 @@ function parseLLVMSegment(segment) {
Types.needAnalysis[type] = 0;
return {
intertype: 'structvalue',
values: splitTokenList(segment[1].tokens).map(parseLLVMSegment),
params: splitTokenList(segment[1].tokens).map(parseLLVMSegment),
type: type
};
} else if (segment[0].text in PARSABLE_LLVM_FUNCTIONS) {
@ -1458,7 +1458,7 @@ function finalizeLLVMParameter(param, noIndexizeFunctions) {
}
ret = parseNumerical(ret);
} else if (param.intertype == 'structvalue') {
ret = makeLLVMStruct(param.values.map(function(value) { return finalizeLLVMParameter(value, noIndexizeFunctions) }));
ret = makeLLVMStruct(param.params.map(function(value) { return finalizeLLVMParameter(value, noIndexizeFunctions) }));
} else if (param.intertype === 'blockaddress') {
return finalizeBlockAddress(param);
} else if (param.intertype === 'type') {
@ -1793,7 +1793,7 @@ function processMathop(item) {
// Walks through some intertype data, calling a function at every item. If
// the function returns true, will stop the walk.
// TODO: Use this in analyzer, possibly also in jsifier
// TODO: Use this more in analyzer, possibly also in jsifier
function walkInterdata(item, pre, post, obj) {
if (!item || !item.intertype) return false;
if (pre && pre(item, obj)) return true;

42
tests/cases/lifetime.ll Normal file
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@ -0,0 +1,42 @@
; ModuleID = '/tmp/emscripten/tmp/src.cpp.o'
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
target triple = "i386-pc-linux-gnu"
%struct.vec2 = type { float, float }
@.str = private unnamed_addr constant [15 x i8] c"hello, world!\0A\00" ; [#uses=1]
; [#uses=1]
declare i32 @printf(i8* noalias, ...)
define linkonce_odr float @vec2Length(%struct.vec2* %this) nounwind align 2 {
entry:
%__first.addr.i = alloca %struct.b2Pair.5*, align 4 ; [#uses=3 type=%struct.b2Pair.5**]
%__last.addr.i = alloca %struct.b2Pair.5*, align 4 ; [#uses=3 type=%struct.b2Pair.5**]
%__comp.addr.i = alloca %struct.b2Pair.5*, align 4 ; [#uses=2 type=%struct.b2Pair.5**]
%13 = bitcast %struct.vec2** %__first.addr.i to i8* ; [#uses=1 type=i8*]
call void @llvm.lifetime.start(i64 -1, i8* %13)
%14 = bitcast %struct.vec2** %__last.addr.i to i8* ; [#uses=1 type=i8*]
call void @llvm.lifetime.start(i64 -1, i8* %14)
%15 = bitcast i1 (%struct.vec2*, %struct.vec2*)** %__comp.addr.i to i8* ; [#uses=1 type=i8*]
call void @llvm.lifetime.start(i64 -1, i8* %15)
store %struct.vec2* %10, %struct.vec2** %__first.addr.i, align 4
store %struct.vec2* %add.ptr, %struct.vec2** %__last.addr.i, align 4
%18 = bitcast %struct.vec2** %__first.addr.i to i8* ; [#uses=1 type=i8*]
call void @llvm.lifetime.end(i64 -1, i8* %18)
%19 = bitcast %struct.vec2** %__last.addr.i to i8* ; [#uses=1 type=i8*]
call void @llvm.lifetime.end(i64 -1, i8* %19)
%20 = bitcast i1 (%struct.vec2*, %struct.vec2*)** %__comp.addr.i to i8* ; [#uses=1 type=i8*]
call void @llvm.lifetime.end(i64 -1, i8* %20)
}
define i32 @main() {
entry:
%retval = alloca i32, align 4 ; [#uses=1]
store i32 0, i32* %retval
%b = getelementptr inbounds i32* %retval, i32 0, i32 1 ; [#uses=1] ; force __stackBase__ to appear!
%call = call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([15 x i8]* @.str, i32 0, i32 0)) ; [#uses=0]
call i32 (i32)* @nonexistant(i32 %b) ; keep %b alive
ret i32 0
}

6
tests/cases/lifetime.py Normal file
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@ -0,0 +1,6 @@
if Settings.MICRO_OPTS:
assert '__stackBase__' in generated, 'There should be some stack activity (without which, we cannot do the next checks)'
assert '__stackBase__+4' not in generated, 'All variables should have been nativized'
assert '__stackBase__+8' not in generated, 'All variables should have been nativized'
assert 'comp_addr' not in generated, 'This variable should have been eliminated during analysis'

7
tests/runner.py
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@ -3895,7 +3895,7 @@ at function.:blag
for name in glob.glob(path_from_root('tests', 'cases', '*.ll')):
shortname = name.replace('.ll', '')
#if 'break' not in shortname: continue
if '' not in shortname: continue
print "Testing case '%s'..." % shortname
output_file = path_from_root('tests', 'cases', shortname + '.txt')
if Settings.QUANTUM_SIZE == 1:
@ -3908,6 +3908,11 @@ at function.:blag
output = 'hello, world!'
if output.rstrip() != 'skip':
self.do_ll_run(path_from_root('tests', 'cases', name), output)
# Optional source checking, a python script that gets a global generated with the source
src_checker = path_from_root('tests', 'cases', shortname + '.py')
if os.path.exists(src_checker):
generated = open('src.cpp.o.js').read()
exec(open(src_checker).read())
# Autodebug the code
def do_autodebug(self, filename):