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llvm-mirror/lib/Target/ARM/AsmPrinter
Evan Cheng d615e606c4 Change Thumb2 jumptable codegen to one that uses two level jumps:
Before:
      adr r12, #LJTI3_0_0
      ldr pc, [r12, +r0, lsl #2]
LJTI3_0_0:
      .long    LBB3_24
      .long    LBB3_30
      .long    LBB3_31
      .long    LBB3_32

After:
      adr r12, #LJTI3_0_0
      add pc, r12, +r0, lsl #2
LJTI3_0_0:
      b.w    LBB3_24
      b.w    LBB3_30
      b.w    LBB3_31
      b.w    LBB3_32

This has several advantages.
1. This will make it easier to optimize this to a TBB / TBH instruction +
   (smaller) table.
2. This eliminate the need for ugly asm printer hack to force the address
   into thumb addresses (bit 0 is one).
3. Same codegen for pic and non-pic.
4. This eliminate the need to align the table so constantpool island pass
   won't have to over-estimate the size.

Based on my calculation, the later is probably slightly faster as well since
ldr pc with shifter address is very slow. That is, it should be a win as long
as the HW implementation can do a reasonable job of branch predict the second
branch.

llvm-svn: 77024
2009-07-25 00:33:29 +00:00
..
ARMAsmPrinter.cpp Change Thumb2 jumptable codegen to one that uses two level jumps: 2009-07-25 00:33:29 +00:00
CMakeLists.txt Add missing dependencies to the CMake build system. 2009-06-25 05:03:06 +00:00
Makefile Removed trailing whitespace from Makefiles. 2009-01-09 16:44:42 +00:00