Clean up the handling of the x87 fp stack to make it more robust.

Drop the FpMov instructions, use plain COPY instead.

Drop the FpSET/GET instruction for accessing fixed stack positions.
Instead use normal COPY to/from ST registers around inline assembly, and
provide a single new FpPOP_RETVAL instruction that can access the return
value(s) from a call. This is still necessary since you cannot tell from
the CALL instruction alone if it returns anything on the FP stack. Teach
fast isel to use this.

This provides a much more robust way of handling fixed stack registers -
we can tolerate arbitrary FP stack instructions inserted around calls
and inline assembly. Live range splitting could sometimes break x87 code
by inserting spill code in unfortunate places.

As a bonus we handle floating point inline assembly correctly now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134018 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 12 deletions

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 48f60f8..9e4fdad 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -500,18 +500,6 @@ BitVector X86RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
     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);
-
   // Mark the segment registers as reserved.
   Reserved.set(X86::CS);
   Reserved.set(X86::SS);