Add infrastructure for support of multiple memory constraints.

Summary:
The operand flag word for ISD::INLINEASM nodes now contains a 15-bit
memory constraint ID when the operand kind is Kind_Mem. This constraint
ID is a numeric equivalent to the constraint code string and is converted
with a target specific hook in TargetLowering.

This patch maps all memory constraints to InlineAsm::Constraint_m so there
is no functional change at this point. It just proves that using these
previously unused bits in the encoding of the flag word doesn't break anything.

The next patch will make each target preserve the current mapping of
everything to Constraint_m for itself while changing the target independent
implementation of the hook to return Constraint_Unknown appropriately. Each
target will then be adapted in separate patches to use appropriate Constraint_*
values.

Reviewers: hfinkel

Reviewed By: hfinkel

Subscribers: hfinkel, jholewinski, llvm-commits

Differential Revision: http://reviews.llvm.org/D8171


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232027 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMISelDAGToDAG.cpp

@@ -257,7 +257,7 @@ private:
 
   /// SelectInlineAsmMemoryOperand - Implement addressing mode selection for
   /// inline asm expressions.
-  bool SelectInlineAsmMemoryOperand(const SDValue &Op, char ConstraintCode,
+  bool SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
                                     std::vector<SDValue> &OutOps) override;
 
   // Form pairs of consecutive R, S, D, or Q registers.
@@ -3472,9 +3472,10 @@ SDNode *ARMDAGToDAGISel::SelectInlineAsm(SDNode *N){
 
 
 bool ARMDAGToDAGISel::
-SelectInlineAsmMemoryOperand(const SDValue &Op, char ConstraintCode,
+SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
                              std::vector<SDValue> &OutOps) {
-  assert(ConstraintCode == 'm' && "unexpected asm memory constraint");
+  assert(ConstraintID == InlineAsm::Constraint_m &&
+         "unexpected asm memory constraint");
   // Require the address to be in a register.  That is safe for all ARM
   // variants and it is hard to do anything much smarter without knowing
   // how the operand is used.