[MachineLICM] Add functions to MachineLICM to hoist invariant stores

This patch adds functions to allow MachineLICM to hoist invariant stores.
Currently, MachineLICM does not hoist any store instructions, however
when storing the same value to a constant spot on the stack, the store
instruction should be considered invariant and be hoisted. The function
isInvariantStore iterates each operand of the store instruction and checks
that each register operand satisfies isCallerPreservedPhysReg. The store
may be fed by a copy, which is hoisted by isCopyFeedingInvariantStore.
This patch also adds the PowerPC changes needed to consider the stack
register as caller preserved.

Differential Revision: https://reviews.llvm.org/D40196

llvm-svn: 327856

1 files changed, 23 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetRegisterInfo.cpp b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
index 5db1c58d349..8b5cd3e73ac 100644
--- a/llvm/lib/CodeGen/TargetRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
@@ -472,6 +472,29 @@ unsigned TargetRegisterInfo::getRegSizeInBits(unsigned Reg,
   return getRegSizeInBits(*RC);
 }
 
+unsigned
+TargetRegisterInfo::lookThruCopyLike(unsigned SrcReg,
+                                     const MachineRegisterInfo *MRI) const {
+  while (true) {
+    const MachineInstr *MI = MRI->getVRegDef(SrcReg);
+    if (!MI->isCopyLike())
+      return SrcReg;
+
+    unsigned CopySrcReg;
+    if (MI->isCopy())
+      CopySrcReg = MI->getOperand(1).getReg();
+    else {
+      assert(MI->isSubregToReg() && "Bad opcode for lookThruCopyLike");
+      CopySrcReg = MI->getOperand(2).getReg();
+    }
+
+    if (!isVirtualRegister(CopySrcReg))
+      return CopySrcReg;
+
+    SrcReg = CopySrcReg;
+  }
+}
+
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD
 void TargetRegisterInfo::dumpReg(unsigned Reg, unsigned SubRegIndex,