Mark the x86 fp stack registers as "reserved". This tells LiveVariables

and the RegisterScavenger not to expect traditional liveness
techniques are applicable to these registers, since we don't fully
modify the effects of push and pop after stackification.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61179 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 85c58d57e9b367badd69497a6d27c74c9d66c2f1..4bdfd8c101d92352ca44c7089d41175678e76741 100644 (file)
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -263,16 +263,30 @@ X86RegisterInfo::getCalleeSavedRegClasses(const MachineFunction *MF) const {
 
 BitVector X86RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
   BitVector Reserved(getNumRegs());
+  // Set the stack-pointer register and its aliases as reserved.
   Reserved.set(X86::RSP);
   Reserved.set(X86::ESP);
   Reserved.set(X86::SP);
   Reserved.set(X86::SPL);
+  // Set the frame-pointer register and its aliases as reserved if needed.
   if (hasFP(MF)) {
     Reserved.set(X86::RBP);
     Reserved.set(X86::EBP);
     Reserved.set(X86::BP);
     Reserved.set(X86::BPL);
   }
+  // Mark the x87 stack registers as reserved, since they don't
+  // behave normally with respect to liveness. We don't fully
+  // model the effects of x87 stack pushes and pops after
+  // stackification.
+  Reserved.set(X86::ST0);
+  Reserved.set(X86::ST1);
+  Reserved.set(X86::ST2);
+  Reserved.set(X86::ST3);
+  Reserved.set(X86::ST4);
+  Reserved.set(X86::ST5);
+  Reserved.set(X86::ST6);
+  Reserved.set(X86::ST7);
   return Reserved;
 }