Subzero: Make the register allocator more robust with -reg-use and -reg-exclude.
The problem is that if you too aggressively -reg-use or -reg-exclude, you can get failures because of inherently high register pressure, and there are also contributions from the "specialty" register classes.
For example, when you combine load optimization, address mode inference, local register availability optimization, and the div instruction, you can end up needing 5 simultaneously live infinite-weight registers.
The fix/enhancement here is to keep track of the "reserve" set of registers for each register class, and allow the register allocator to draw from that as a last resort. This behavior is guarded by the -reg-reserve flag.
This CL also includes two improvements in lowering sequences to reduce register pressure.
BUG= none
R=kschimpf@google.com
Review URL: https://codereview.chromium.org/1641653004 .
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index 4e50248..99c55ac 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -55,6 +55,30 @@
Cfg::~Cfg() { assert(ICE_TLS_GET_FIELD(CurrentCfg) == nullptr); }
+/// Create a string like "foo(i=123:b=9)" indicating the function name, number
+/// of high-level instructions, and number of basic blocks. This string is only
+/// used for dumping and other diagnostics, and the idea is that given a set of
+/// functions to debug a problem on, it's easy to find the smallest or simplest
+/// function to attack. Note that the counts may change somewhat depending on
+/// what point it is called during the translation passes.
+IceString Cfg::getFunctionNameAndSize() const {
+ if (!BuildDefs::dump())
+ return getFunctionName();
+ SizeT NodeCount = 0;
+ SizeT InstCount = 0;
+ for (CfgNode *Node : getNodes()) {
+ ++NodeCount;
+ // Note: deleted instructions are *not* ignored.
+ InstCount += Node->getPhis().size();
+ for (Inst &I : Node->getInsts()) {
+ if (!llvm::isa<InstTarget>(&I))
+ ++InstCount;
+ }
+ }
+ return getFunctionName() + "(i=" + std::to_string(InstCount) + ":b=" +
+ std::to_string(NodeCount) + ")";
+}
+
void Cfg::setError(const IceString &Message) {
HasError = true;
ErrorMessage = Message;
@@ -1075,7 +1099,9 @@
Str << Args[i]->getType() << " ";
Args[i]->dump(this);
}
- Str << ") {\n";
+ // Append an extra copy of the function name here, in order to print its
+ // size stats but not mess up lit tests.
+ Str << ") { # " << getFunctionNameAndSize() << "\n";
}
resetCurrentNode();
if (isVerbose(IceV_Liveness)) {
