[GlobalISel] Defer setting HasCalls on MachineFrameInfo to selection time.

We currently always set the HasCalls on MFI during translation and legalization if
we're handling a call or legalizing to a libcall. However, if that call is later
optimized to a tail call then we don't need the flag. The flag being set to true
causes frame lowering to always save and restore FP/LR, which adds unnecessary code.

This change does the same thing as SelectionDAG and ports over some code that scans
instructions after selection, using TargetInstrInfo to determine if target opcodes
are known calls.

Code size geomean improvements on CTMark:
 -O0 : 0.1%
 -Os : 0.3%

Differential Revision: https://reviews.llvm.org/D67868

llvm-svn: 372443

3 files changed, 21 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index c44532e240f..74365af7a2b 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -1564,7 +1564,9 @@ bool IRTranslator::translateCallSite(const ImmutableCallSite &CS,
     Args.push_back(getOrCreateVRegs(*Arg));
   }
 
-  MF->getFrameInfo().setHasCalls(true);
+  // We don't set HasCalls on MFI here yet because call lowering may decide to
+  // optimize into tail calls. Instead, we defer that to selection where a final
+  // scan is done to check if any instructions are calls.
   bool Success =
       CLI->lowerCall(MIRBuilder, CS, Res, Args, SwiftErrorVReg,
                      [&]() { return getOrCreateVReg(*CS.getCalledValue()); });
diff --git a/llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp b/llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp
index bf441afc9dc..7c4fd2d140d 100644
--- a/llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp
@@ -17,7 +17,9 @@
 #include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
 #include "llvm/CodeGen/GlobalISel/Utils.h"
 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
 #include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/CodeGen/TargetPassConfig.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
@@ -223,6 +225,22 @@ bool InstructionSelect::runOnMachineFunction(MachineFunction &MF) {
   auto &TLI = *MF.getSubtarget().getTargetLowering();
   TLI.finalizeLowering(MF);
 
+  // Determine if there are any calls in this machine function. Ported from
+  // SelectionDAG.
+  MachineFrameInfo &MFI = MF.getFrameInfo();
+  for (const auto &MBB : MF) {
+    if (MFI.hasCalls() && MF.hasInlineAsm())
+      break;
+
+    for (const auto &MI : MBB) {
+      if ((MI.isCall() && !MI.isReturn()) || MI.isStackAligningInlineAsm())
+        MFI.setHasCalls(true);
+      if (MI.isInlineAsm())
+        MF.setHasInlineAsm(true);
+    }
+  }
+
+
   LLVM_DEBUG({
     dbgs() << "Rules covered by selecting function: " << MF.getName() << ":";
     for (auto RuleID : CoverageInfo.covered())
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index d4ae3b52a46..f2b37eada2e 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -364,8 +364,6 @@ llvm::createLibcall(MachineIRBuilder &MIRBuilder, RTLIB::Libcall Libcall,
   auto &TLI = *MIRBuilder.getMF().getSubtarget().getTargetLowering();
   const char *Name = TLI.getLibcallName(Libcall);
 
-  MIRBuilder.getMF().getFrameInfo().setHasCalls(true);
-
   CallLowering::CallLoweringInfo Info;
   Info.CallConv = TLI.getLibcallCallingConv(Libcall);
   Info.Callee = MachineOperand::CreateES(Name);
@@ -430,7 +428,6 @@ llvm::createMemLibcall(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI,
   const char *Name = TLI.getLibcallName(RTLibcall);
 
   MIRBuilder.setInstr(MI);
-  MIRBuilder.getMF().getFrameInfo().setHasCalls(true);
 
   CallLowering::CallLoweringInfo Info;
   Info.CallConv = TLI.getLibcallCallingConv(RTLibcall);