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authorPaul Berry <[email protected]>2013-11-27 17:57:19 -0800
committerPaul Berry <[email protected]>2013-12-09 10:54:26 -0800
commit2c17f97fe6a40e4a963fb4eec0ea0555f562b1be (patch)
tree2211956818d4250465da8176f800654016802188 /src/glsl/ir.cpp
parent97d8b770549584a2cd6b14956f15beeef0d83cad (diff)
glsl/loops: consolidate bounded loop handling into a lowering pass.
Previously, all of the back-ends (ir_to_mesa, st_glsl_to_tgsi, and the i965 fs and vec4 visitors) had nearly identical logic for handling bounded loops. This replaces the duplicate logic with an equivalent lowering pass that is used by all the back-ends. Note: on i965, there is a slight increase in instruction count. For example, a loop like this: for (int i = 0; i < 100; i++) { total += i; } would previously compile down to this (vec4) native code: mov(8) g4<1>.xD 0D mov(8) g8<1>.xD 0D loop: cmp.ge.f0(8) null g8<4;4,1>.xD 100D (+f0) break(8) add(8) g5<1>.xD g5<4;4,1>.xD g4<4;4,1>.xD add(8) g8<1>.xD g8<4;4,1>.xD 1D add(8) g4<1>.xD g4<4;4,1>.xD 1D while(8) loop After this patch, the "(+f0) break(8)" turns into: (+f0) if(8) break(8) endif(8) because the back-end isn't smart enough to recognize that "if (condition) break;" can be done using a conditional break instruction. However, it should be relatively easy for a future peephole optimization to properly optimize this. Reviewed-by: Jordan Justen <[email protected]> Reviewed-by: Ian Romanick <[email protected]>
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