Subzero: Decorate the text asm output with register availability info.
The -asm-verbose flag adds comments to the text asm output about register availability. Specifically, it prints the registers in use at the beginning and end of each block, and it prints which registers' live ranges end at each instruction.
This is extremely helpful when studying the output to find opportunities to improve the code quality.
BUG= none
R=jvoung@chromium.org
Review URL: https://codereview.chromium.org/682983004
diff --git a/src/IceCfgNode.cpp b/src/IceCfgNode.cpp
index 661dd73..b753078 100644
--- a/src/IceCfgNode.cpp
+++ b/src/IceCfgNode.cpp
@@ -756,9 +756,12 @@
return;
Inst *Branch = NULL;
for (Inst *I : Insts) {
- if (!I->isDeleted() && !I->isUnconditionalBranch())
+ if (I->isDeleted())
+ continue;
+ if (I->isUnconditionalBranch())
+ Branch = I;
+ else if (!I->isRedundantAssign())
return;
- Branch = I;
}
Branch->setDeleted();
assert(OutEdges.size() == 1);
@@ -798,9 +801,73 @@
// ======================== Dump routines ======================== //
+namespace {
+
+// Helper functions for emit().
+
+void emitRegisterUsage(Ostream &Str, const Cfg *Func, const CfgNode *Node,
+ bool IsLiveIn, std::vector<SizeT> &LiveRegCount) {
+ Liveness *Liveness = Func->getLiveness();
+ const LivenessBV *Live;
+ if (IsLiveIn) {
+ Live = &Liveness->getLiveIn(Node);
+ Str << "\t\t\t\t# LiveIn=";
+ } else {
+ Live = &Liveness->getLiveOut(Node);
+ Str << "\t\t\t\t# LiveOut=";
+ }
+ if (!Live->empty()) {
+ bool First = true;
+ for (SizeT i = 0; i < Live->size(); ++i) {
+ if ((*Live)[i]) {
+ Variable *Var = Liveness->getVariable(i, Node);
+ if (Var->hasReg()) {
+ if (IsLiveIn)
+ ++LiveRegCount[Var->getRegNum()];
+ if (!First)
+ Str << ",";
+ First = false;
+ Var->emit(Func);
+ }
+ }
+ }
+ }
+ Str << "\n";
+}
+
+void emitLiveRangesEnded(Ostream &Str, const Cfg *Func, const Inst *Instr,
+ std::vector<SizeT> &LiveRegCount) {
+ bool First = true;
+ Variable *Dest = Instr->getDest();
+ if (Dest && Dest->hasReg())
+ ++LiveRegCount[Dest->getRegNum()];
+ for (SizeT I = 0; I < Instr->getSrcSize(); ++I) {
+ Operand *Src = Instr->getSrc(I);
+ SizeT NumVars = Src->getNumVars();
+ for (SizeT J = 0; J < NumVars; ++J) {
+ const Variable *Var = Src->getVar(J);
+ if (Var->hasReg()) {
+ if (Instr->isLastUse(Var) &&
+ --LiveRegCount[Var->getRegNum()] == 0) {
+ if (First)
+ Str << " \t# END=";
+ else
+ Str << ",";
+ Var->emit(Func);
+ First = false;
+ }
+ }
+ }
+ }
+}
+
+} // end of anonymous namespace
+
void CfgNode::emit(Cfg *Func) const {
Func->setCurrentNode(this);
Ostream &Str = Func->getContext()->getStrEmit();
+ Liveness *Liveness = Func->getLiveness();
+ bool DecorateAsm = Liveness && Func->getContext()->getFlags().DecorateAsm;
if (Func->getEntryNode() == this) {
Str << Func->getContext()->mangleName(Func->getFunctionName()) << ":\n";
}
@@ -809,6 +876,10 @@
Assembler *Asm = Func->getAssembler<Assembler>();
Asm->BindCfgNodeLabel(getIndex());
}
+ std::vector<SizeT> LiveRegCount(Func->getTarget()->getNumRegisters());
+ if (DecorateAsm)
+ emitRegisterUsage(Str, Func, this, true, LiveRegCount);
+
for (InstPhi *Phi : Phis) {
if (Phi->isDeleted())
continue;
@@ -819,10 +890,18 @@
for (Inst *I : Insts) {
if (I->isDeleted())
continue;
+ if (I->isRedundantAssign()) {
+ Variable *Dest = I->getDest();
+ if (DecorateAsm && Dest->hasReg() && !I->isLastUse(I->getSrc(0)))
+ ++LiveRegCount[Dest->getRegNum()];
+ continue;
+ }
if (Func->useIntegratedAssembler()) {
I->emitIAS(Func);
} else {
I->emit(Func);
+ if (DecorateAsm)
+ emitLiveRangesEnded(Str, Func, I, LiveRegCount);
Str << "\n";
}
// Update emitted instruction count, plus fill/spill count for
@@ -841,6 +920,8 @@
}
}
}
+ if (DecorateAsm)
+ emitRegisterUsage(Str, Func, this, false, LiveRegCount);
}
void CfgNode::dump(Cfg *Func) const {
