[llvm] ac6a0cd - [X86][AArch64][NFC] Simplify querying used argument registers

[Bill Wendling via llvm-commits]

Author: Bill Wendling
Date: 2022-08-19T11:39:05-07:00
New Revision: ac6a0cdc2e85d69ec20fd31d29f30843db0943bd

URL: https://github.com/llvm/llvm-project/commit/ac6a0cdc2e85d69ec20fd31d29f30843db0943bd
DIFF: https://github.com/llvm/llvm-project/commit/ac6a0cdc2e85d69ec20fd31d29f30843db0943bd.diff

LOG: [X86][AArch64][NFC] Simplify querying used argument registers

Registers used for arguments are listed as "live-ins" into the starting
basic block. This means we don't have to go through a potentially
expensive search through all possible argument registers when we only
care about used argument registers.

Differential Revision: https://reviews.llvm.org/D132181

Added: 
    

Modified: 
    llvm/lib/CodeGen/PrologEpilogInserter.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 89a43c4f57f6b..64536bf324a25 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1206,6 +1206,11 @@ void PEI::insertZeroCallUsedRegs(MachineFunction &MF) {
             UsedRegs.set(Reg);
         }
 
+  // Get a list of registers that are used.
+  BitVector LiveIns(TRI.getNumRegs());
+  for (const MachineBasicBlock::RegisterMaskPair &LI : MF.front().liveins())
+    LiveIns.set(LI.PhysReg);
+
   BitVector RegsToZero(TRI.getNumRegs());
   for (MCRegister Reg : AllocatableSet.set_bits()) {
     // Skip over fixed registers.
@@ -1221,8 +1226,14 @@ void PEI::insertZeroCallUsedRegs(MachineFunction &MF) {
       continue;
 
     // Want only registers used for arguments.
-    if (OnlyArg && !TRI.isArgumentRegister(MF, Reg))
-      continue;
+    if (OnlyArg) {
+      if (OnlyUsed) {
+        if (!LiveIns[Reg])
+          continue;
+      } else if (!TRI.isArgumentRegister(MF, Reg)) {
+        continue;
+      }
+    }
 
     RegsToZero.set(Reg);
   }