add doesn't need to overflow between the two 16-bit chunks.
* Implement pre/post increment support. (e.g. PR935)
-* Coalesce stack slots!
* Implement smarter constant generation for binops with large immediates.
-* Consider materializing FP constants like 0.0f and 1.0f using integer
- immediate instructions then copy to FPU. Slower than load into FPU?
+A few ARMv6T2 ops should be pattern matched: BFI, SBFX, and UBFX
+
+Interesting optimization for PIC codegen on arm-linux:
+http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43129
//===---------------------------------------------------------------------===//
//===---------------------------------------------------------------------===//
-We currently compile abs:
-int foo(int p) { return p < 0 ? -p : p; }
-
-into:
-
-_foo:
- rsb r1, r0, #0
- cmn r0, #1
- movgt r1, r0
- mov r0, r1
- bx lr
-
-This is very, uh, literal. This could be a 3 operation sequence:
- t = (p sra 31);
- res = (p xor t)-t
-
-Which would be better. This occurs in png decode.
-
-//===---------------------------------------------------------------------===//
-
More load / store optimizations:
1) Better representation for block transfer? This is from Olden/power:
4) Once we added support for multiple result patterns, write indexed loads
patterns instead of C++ instruction selection code.
-5) Use FLDM / FSTM to emulate indexed FP load / store.
+5) Use VLDM / VSTM to emulate indexed FP load / store.
//===---------------------------------------------------------------------===//
//===---------------------------------------------------------------------===//
-More register scavenging work:
-
-1. Use the register scavenger to track frame index materialized into registers
- (those that do not fit in addressing modes) to allow reuse in the same BB.
-2. Finish scavenging for Thumb.
-
-//===---------------------------------------------------------------------===//
-
More LSR enhancements possible:
1. Teach LSR about pre- and post- indexed ops to allow iv increment be merged
//===---------------------------------------------------------------------===//
-We need to fix constant isel for ARMv6t2 to use MOVT.
-
-//===---------------------------------------------------------------------===//
-
Constant island pass should make use of full range SoImm values for LEApcrel.
Be careful though as the last attempt caused infinite looping on lencod.
//===---------------------------------------------------------------------===//
-add/sub/and/or + i32 imm can be simplified by folding part of the immediate
-into the operation.
-
-//===---------------------------------------------------------------------===//
-
It might be profitable to cse MOVi16 if there are lots of 32-bit immediates
with the same bottom half.
//===---------------------------------------------------------------------===//
Make use of the "rbit" instruction.
+
+//===---------------------------------------------------------------------===//
+
+Take a look at test/CodeGen/Thumb2/machine-licm.ll. ARM should be taught how
+to licm and cse the unnecessary load from cp#1.
+
+//===---------------------------------------------------------------------===//
+
+The CMN instruction sets the flags like an ADD instruction, while CMP sets
+them like a subtract. Therefore to be able to use CMN for comparisons other
+than the Z bit, we'll need additional logic to reverse the conditionals
+associated with the comparison. Perhaps a pseudo-instruction for the comparison,
+with a post-codegen pass to clean up and handle the condition codes?
+See PR5694 for testcase.