[llvm-commits] [PATCH] Add Pattern ID Information

[David Greene]

I've got a patch series ready to implement support for printing asm comments
about instruction selection.  For example:

        incq    %rdx                    # test.c:38
                                        #  Src: (add:i64 GR64:i64:$src, 1:i64)
                                        #  Dst: (INC64r:i64 GR64:i64:$src)

This is really helpful for tracking down isel issues and was invaluable during
AVX implementation and tuning.  So I want to get this in before I start doing
the heavy-duty AVX merging.

There are only two patches in the series that are probably worth reviewing
before commit.  This is the first.  It adds a new field to MachineInstr
to hold an index into a table of strings generated by TableGen.  That table
continues the pattern information to dump out for the instruction.

For hosts with 64-bit pointers, this change should not affect the size of
MachineInstr at all.  For hosts with 32-bit pointers, it could increase the
size of MachineInstr by 16 or 32 bits depending on how std::vector is
defined.

Since pattern information will only be available in debug builds, I considered
guarding the field with #ifndef NDEBUG but experience tells me to be leery
about defining key data structures differently in debug and non-debug builds.
I am ok adding the guards if folks think that's a good idea.

Comments and suggestions?

                                 -Dave

=============

Add a field to carry an index into a pattern string table for debug
comment printing purposes.
---
 llvm/include/llvm/CodeGen/MachineInstr.h |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git old/llvm/include/llvm/CodeGen/MachineInstr.h new/llvm/include/llvm/CodeGen/MachineInstr.h
index 5b3d3ea..b03b5d2 100644
--- old/llvm/include/llvm/CodeGen/MachineInstr.h
+++ new/llvm/include/llvm/CodeGen/MachineInstr.h
@@ -72,6 +72,14 @@ private:
                                         // anything other than to convey comment
                                         // information to AsmPrinter.
 
+  int16_t PatternIndex;                 // This is an index into a
+                                        // table of instruction
+                                        // pattern strings.  The asm
+                                        // printer uses this index to
+                                        // get the string it should
+                                        // print out for pattern match
+                                        // comments.
+
   std::vector<MachineOperand> Operands; // the operands
   mmo_iterator MemRefs;                 // information on memory references
   mmo_iterator MemRefsEnd;
-- 
1.7.6