Chris Lattner c41cc83117 Naturally align doubles in the constant pool, set PrivateGlobalPrefix on
darwin, use it when printing the constant pool indices so the labels are
appropriately private, emit cp entries to .const instead of .data on darwin
and only emit a single .section for the constant pool, not one for each
entry.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24440 91177308-0d34-0410-b5e6-96231b3b80d8
2005-11-21 06:46:22 +00:00
..
2004-11-21 00:01:54 +00:00
2005-04-21 23:38:14 +00:00
2005-11-20 22:13:18 +00:00
2005-07-22 20:49:37 +00:00
2005-04-21 23:38:14 +00:00

//===---------------------------------------------------------------------===//
// Random ideas for the X86 backend.
//===---------------------------------------------------------------------===//

Add a MUL2U and MUL2S nodes to represent a multiply that returns both the
Hi and Lo parts (combination of MUL and MULH[SU] into one node).  Add this to
X86, & make the dag combiner produce it when needed.  This will eliminate one
imul from the code generated for:

long long test(long long X, long long Y) { return X*Y; }

by using the EAX result from the mul.  We should add a similar node for
DIVREM.

//===---------------------------------------------------------------------===//

This should be one DIV/IDIV instruction, not a libcall:

unsigned test(unsigned long long X, unsigned Y) {
        return X/Y;
}

This can be done trivially with a custom legalizer.  What about overflow 
though?  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14224

//===---------------------------------------------------------------------===//

Need to add support for rotate instructions.

//===---------------------------------------------------------------------===//

Some targets (e.g. athlons) prefer freep to fstp ST(0):
http://gcc.gnu.org/ml/gcc-patches/2004-04/msg00659.html

//===---------------------------------------------------------------------===//

This should use faddi on chips where it is profitable:
double foo(double P, int *I) { return P+*I; }

//===---------------------------------------------------------------------===//

The FP stackifier needs to be global.  Also, it should handle simple permutates
to reduce number of shuffle instructions, e.g. turning:

fld P	->		fld Q
fld Q			fld P
fxch

or:

fxch	->		fucomi
fucomi			jl X
jg X

//===---------------------------------------------------------------------===//

Improvements to the multiply -> shift/add algorithm:
http://gcc.gnu.org/ml/gcc-patches/2004-08/msg01590.html

//===---------------------------------------------------------------------===//

Improve code like this (occurs fairly frequently, e.g. in LLVM):
long long foo(int x) { return 1LL << x; }

http://gcc.gnu.org/ml/gcc-patches/2004-09/msg01109.html
http://gcc.gnu.org/ml/gcc-patches/2004-09/msg01128.html
http://gcc.gnu.org/ml/gcc-patches/2004-09/msg01136.html

Another useful one would be  ~0ULL >> X and ~0ULL << X.

//===---------------------------------------------------------------------===//

Should support emission of the bswap instruction, probably by adding a new
DAG node for byte swapping.  Also useful on PPC which has byte-swapping loads.