Checkin in of first of several patches to finish implementation of

mips16/mips32 floating point interoperability. 

This patch fixes returns from mips16 functions so that if the function
was in fact called by a mips32 hard float routine, then values
that would have been returned in floating point registers are so returned.

Mips16 mode has no floating point instructions so there is no way to
load values into floating point registers.

This is needed when returning float, double, single complex, double complex
in the Mips ABI.

Helper functions in libc for mips16 are available to do this.

For efficiency purposes, these helper functions have a different calling
convention from normal Mips calls.

Registers v0,v1,a0,a1 are used to pass parameters instead of
a0,a1,a2,a3.

This is because v0,v1,a0,a1 are the natural registers used to return
floating point values in soft float. These values can then be moved
to the appropriate floating point registers with no extra cost.

The only register that is modified is ra in this call.

The helper functions make sure that the return values are in the floating
point registers that they would be in if soft float was not in effect
(which it is for mips16, though the soft float is implemented using a mips32
library that uses hard float).
 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181641 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 2 deletions

diff --git a/lib/Target/Mips/MipsSubtarget.h b/lib/Target/Mips/MipsSubtarget.h
index f2f0e15887..ef7568a813 100644
--- a/lib/Target/Mips/MipsSubtarget.h
+++ b/lib/Target/Mips/MipsSubtarget.h
@@ -93,6 +93,9 @@ protected:
   // InMips16 -- can process Mips16 instructions
   bool InMips16Mode;
 
+  // Mips16 hard float
+  bool InMips16HardFloat;
+
   // PreviousInMips16 -- the function we just processed was in Mips 16 Mode
   bool PreviousInMips16Mode;
 
@@ -170,9 +173,12 @@ public:
     }
     llvm_unreachable("Unexpected mode");
   }
-  bool inMips16ModeDefault() {
+  bool inMips16ModeDefault() const {
     return InMips16Mode;
   }
+  bool inMips16HardFloat() const {
+    return inMips16Mode() && InMips16HardFloat;
+  }
   bool inMicroMipsMode() const { return InMicroMipsMode; }
   bool hasDSP() const { return HasDSP; }
   bool hasDSPR2() const { return HasDSPR2; }
@@ -188,7 +194,8 @@ public:
   bool hasBitCount()  const { return HasBitCount; }
   bool hasFPIdx()     const { return HasFPIdx; }
 
-  bool allowMixed16_32() const { return AllowMixed16_32;};
+  bool allowMixed16_32() const { return inMips16ModeDefault() |
+                                        AllowMixed16_32;}
 
   bool os16() const { return Os16;};