Currently, codegen may spent some time in SDISel passes even if an entire
function is successfully handled by fast-isel. That's because function
arguments are *always* handled by SDISel. Introduce FastLowerArguments to
allow each target to provide hook to handle formal argument lowering.
As a proof-of-concept, add ARMFastIsel::FastLowerArguments to handle
functions with 4 or fewer scalar integer (i8, i16, or i32) arguments. It
completely eliminates the need for SDISel for trivial functions.
rdar://13163905
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174855 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 0d90a07..6c41e1b 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -87,6 +87,27 @@
LastLocalValue = EmitStartPt;
}
+bool FastISel::LowerArguments() {
+ if (!FuncInfo.CanLowerReturn)
+ // Fallback to SDISel argument lowering code to deal with sret pointer
+ // parameter.
+ return false;
+
+ if (!FastLowerArguments())
+ return false;
+
+ // Enter non-dead arguments into ValueMap for uses in non-entry BBs.
+ for (Function::const_arg_iterator I = FuncInfo.Fn->arg_begin(),
+ E = FuncInfo.Fn->arg_end(); I != E; ++I) {
+ if (!I->use_empty()) {
+ DenseMap<const Value *, unsigned>::iterator VI = LocalValueMap.find(I);
+ assert(VI != LocalValueMap.end() && "Missed an argument?");
+ FuncInfo.ValueMap[I] = VI->second;
+ }
+ }
+ return true;
+}
+
void FastISel::flushLocalValueMap() {
LocalValueMap.clear();
LastLocalValue = EmitStartPt;
@@ -836,7 +857,8 @@
void
FastISel::FastEmitBranch(MachineBasicBlock *MSucc, DebugLoc DL) {
- if (FuncInfo.MBB->getBasicBlock()->size() > 1 && FuncInfo.MBB->isLayoutSuccessor(MSucc)) {
+ if (FuncInfo.MBB->getBasicBlock()->size() > 1 &&
+ FuncInfo.MBB->isLayoutSuccessor(MSucc)) {
// For more accurate line information if this is the only instruction
// in the block then emit it, otherwise we have the unconditional
// fall-through case, which needs no instructions.
@@ -1067,6 +1089,10 @@
FastISel::~FastISel() {}
+bool FastISel::FastLowerArguments() {
+ return false;
+}
+
unsigned FastISel::FastEmit_(MVT, MVT,
unsigned) {
return 0;