ARM: Compute MaxCallFrame size early

This exposes a method in MachineFrameInfo that calculates
MaxCallFrameSize and calls it after instruction selection in the ARM
target.

This avoids
ARMBaseRegisterInfo::canRealignStack()/ARMFrameLowering::hasReservedCallFrame()
giving different answers in early/late phases of codegen.

The testcase shows a particular nasty example result of that where we
would fail to properly align an alloca.

Differential Revision: https://reviews.llvm.org/D32622

llvm-svn: 302303

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineFrameInfo.cpp b/llvm/lib/CodeGen/MachineFrameInfo.cpp
index 7de8434df80..73d778ff302 100644
--- a/llvm/lib/CodeGen/MachineFrameInfo.cpp
+++ b/llvm/lib/CodeGen/MachineFrameInfo.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetFrameLowering.h"
+#include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
 #include <cassert>
@@ -175,6 +176,31 @@ unsigned MachineFrameInfo::estimateStackSize(const MachineFunction &MF) const {
   return (unsigned)Offset;
 }
 
+void MachineFrameInfo::computeMaxCallFrameSize(const MachineFunction &MF) {
+  const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
+  unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode();
+  unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
+  assert(FrameSetupOpcode != ~0u && FrameDestroyOpcode != ~0u &&
+         "Can only compute MaxCallFrameSize if Setup/Destroy opcode are known");
+
+  MaxCallFrameSize = 0;
+  for (const MachineBasicBlock &MBB : MF) {
+    for (const MachineInstr &MI : MBB) {
+      unsigned Opcode = MI.getOpcode();
+      if (Opcode == FrameSetupOpcode || Opcode == FrameDestroyOpcode) {
+        unsigned Size = TII.getFrameSize(MI);
+        MaxCallFrameSize = std::max(MaxCallFrameSize, Size);
+        AdjustsStack = true;
+      } else if (MI.isInlineAsm()) {
+        // Some inline asm's need a stack frame, as indicated by operand 1.
+        unsigned ExtraInfo = MI.getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
+        if (ExtraInfo & InlineAsm::Extra_IsAlignStack)
+          AdjustsStack = true;
+      }
+    }
+  }
+}
+
 void MachineFrameInfo::print(const MachineFunction &MF, raw_ostream &OS) const{
   if (Objects.empty()) return;