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6ed53c27ef
With the switch-statement, GCC 4.8.3 produces a small pile of code with a branch. 00000000 <brw_get_index_type>: 000000: 8b 54 24 04 mov 0x4(%esp),%edx 000004: b8 01 00 00 00 mov $0x1,%eax 000009: 81 fa 03 14 00 00 cmp $0x1403,%edx 00000f: 74 0d je 00001e <brw_get_index_type+0x1e> 000011: 31 c0 xor %eax,%eax 000013: 81 fa 05 14 00 00 cmp $0x1405,%edx 000019: 0f 94 c0 sete %al 00001c: 01 c0 add %eax,%eax 00001e: c3 ret However, this could be two instructions. 00000000 <brw_get_index_type>: 000000: 2d 01 14 00 00 sub $0x1401,%eax 000005: d1 e8 shr %eax 000007: 90 nop 000008: 90 nop 000009: 90 nop 00000a: 90 nop 00000b: c3 ret The function was also moved to the header so that it could be inlined at the two call sites. Without this, 32-bit also needs to pull the parameter from the stack. This means there is a push, a call, a move, and a ret added to a two instruction function. The above code shows the function with __attribute__((regparm=1)), but even this adds several extra instructions. There is also an extra instruction on 64-bit to move the parameter to %eax for the subtract. On Bay Trail-D using Fedora 20 compile flags (-m64 -O2 -mtune=generic for 64-bit and -m32 -march=i686 -mtune=atom for 32-bit), affects Gl32Batch7: 32-bit: Difference at 95.0% confidence 0.818589% +/- 0.234661% (n=40) 64-bit: Difference at 95.0% confidence 0.54554% +/- 0.354092% (n=40) Signed-off-by: Ian Romanick <ian.d.romanick@intel.com> Reviewed-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Matt Turner <mattst88@gmail.com> |
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| egl | ||
| gallium | ||
| gbm | ||
| getopt | ||
| glsl | ||
| glx | ||
| gtest | ||
| hgl | ||
| loader | ||
| mapi | ||
| mesa | ||
| util | ||
| Makefile.am | ||
| SConscript | ||