The SSE rsqrt instruction (a fast reciprocal square root estimate) was
grouped in the same scheduling IIC_SSE_SQRT* class as the accurate (but very
slow) SSE sqrt instruction. For code which uses rsqrt (possibly with
newton-raphson iterations) this poor scheduling was affecting performances.
This patch splits off the rsqrt instruction from the sqrt instruction scheduling
classes and creates new IIC_SSE_RSQER* classes with latency values based on
Agner's table.
Differential Revision: http://reviews.llvm.org/D5370
Patch by Simon Pilgrim.
llvm-svn: 218517
Refactoring; no functional changes intended
Removed PostRAScheduler bits from subtargets (X86, ARM).
Added PostRAScheduler bit to MCSchedModel class.
This bit is set by a CPU's scheduling model (if it exists).
Removed enablePostRAScheduler() function from TargetSubtargetInfo and subclasses.
Fixed the existing enablePostMachineScheduler() method to use the MCSchedModel (was just returning false!).
Added methods to TargetSubtargetInfo to allow overrides for AntiDepBreakMode, CriticalPathRCs, and OptLevel for PostRAScheduling.
Added enablePostRAScheduler() function to PostRAScheduler class which queries the subtarget for the above values.
Preserved existing scheduler behavior for ARM, MIPS, PPC, and X86:
a. ARM overrides the CPU's postRA settings by enabling postRA for any non-Thumb or Thumb2 subtarget.
b. MIPS overrides the CPU's postRA settings by enabling postRA for everything.
c. PPC overrides the CPU's postRA settings by enabling postRA for everything.
d. X86 is the only target that actually has postRA specified via sched model info.
Differential Revision: http://reviews.llvm.org/D4217
llvm-svn: 213101
The old method used by X86TTI to determine partial-unrolling thresholds was
messy (because it worked by testing target features), and also would not
correctly identify the target CPU if certain target features were disabled.
After some discussions on IRC with Chandler et al., it was decided that the
processor scheduling models were the right containers for this information
(because it is often tied to special uop dispatch-buffer sizes).
This does represent a small functionality change:
- For generic x86-64 (which uses the SB model and, thus, will get some
unrolling).
- For AMD cores (because they still currently use the SB scheduling model)
- For Haswell (based on benchmarking by Louis Gerbarg, it was decided to bump
the default threshold to 50; we're working on a test case for this).
Otherwise, nothing has changed for any other targets. The logic, however, has
been moved into BasicTTI, so other targets may now also opt-in to this
functionality simply by setting LoopMicroOpBufferSize in their processor
model definitions.
llvm-svn: 208289
This model is not final and work is still in progress.
However there are substantial improvements on integer tests mainly because of better RAL with new scheduler.
Differential Revision: http://reviews.llvm.org/D3451
llvm-svn: 206957
Implements Instruction scheduler latencies for Silvermont,
using latencies from the Intel Silvermont Optimization Guide.
Auto detects SLM.
Turns on post RA scheduler when generating code for SLM.
llvm-svn: 190717
Andrea Di Biagio