1 //===-- SIModeRegister.cpp - Mode Register --------------------------------===//
9 /// This pass inserts changes to the Mode register settings as required.
11 /// rounding mode setting, but is intended to be generic enough to be easily
23 #define DEBUG_TYPE "si-mode-register"
25 STATISTIC(NumSetregInserted, "Number of setreg of mode register inserted.");
30   // Mask is a bitmask where a '1' indicates the corresponding Mode bit has a
33   unsigned Mode = 0;  member
37   Status(unsigned NewMask, unsigned NewMode) : Mask(NewMask), Mode(NewMode) {  in Status()
38     Mode &= Mask;  in Status()
44     return Status((Mask | S.Mask), ((Mode & ~S.Mask) | (S.Mode & S.Mask)));  in merge()
50     return Status(Mask & ~newMask, Mode & ~newMask);  in mergeUnknown()
53   // intersect two Status values to produce a mode and mask that is a subset
56     unsigned NewMask = (Mask & S.Mask) & (Mode ^ ~S.Mode);  in intersect()
57     unsigned NewMode = (Mode & NewMask);  in intersect()
61   // produce the delta required to change the Mode to the required Mode
63     return Status((S.Mask & (Mode ^ S.Mode)) | (~Mask & S.Mask), S.Mode);  in delta()
67     return (Mask == S.Mask) && (Mode == S.Mode);  in operator ==()
73     return ((Mask & S.Mask) == S.Mask) && ((Mode & S.Mask) == S.Mode);  in isCompatible()
81   // The Status that represents the mode register settings required by the
85   // The Status that represents the net changes to the Mode register made by
89   // The Status that represents the mode register settings on exit from this
93   // The Status that represents the intersection of exit Mode register settings
97   // In Phase 1 we record the first instruction that has a mode requirement,
98   // which is used in Phase 3 if we need to insert a mode change.
115   // The default mode register setting currently only caters for the floating
116   // point double precision rounding mode.
117   // We currently assume the default rounding mode is Round to Nearest
118   // NOTE: this should come from a per function rounding mode setting once such
156                 "Insert required mode register values", false, false)
166 // Determine the Mode register setting required for this instruction.
167 // Instructions which don't use the Mode register return a null Status.
186       unsigned Mode = MI.getOperand(2).getImm();  in getInstructionMode()  local
189       return Status(FP_ROUND_MODE_DP(3), FP_ROUND_MODE_DP(Mode));  in getInstructionMode()
192       unsigned Mode = MI.getOperand(2).getImm();  in getInstructionMode()  local
195       return Status(FP_ROUND_MODE_DP(3), FP_ROUND_MODE_DP(Mode));  in getInstructionMode()
198       unsigned Mode = MI.getOperand(6).getImm();  in getInstructionMode()  local
201       return Status(FP_ROUND_MODE_DP(3), FP_ROUND_MODE_DP(Mode));  in getInstructionMode()
204       unsigned Mode = MI.getOperand(2).getImm();  in getInstructionMode()  local
207       return Status(FP_ROUND_MODE_DP(3), FP_ROUND_MODE_DP(Mode));  in getInstructionMode()
216 // Insert a setreg instruction to update the Mode register.
218 // the value of disjoint parts of the Mode register when we don't know the
226     unsigned Value = (InstrMode.Mode >> Offset) & ((1 << Width) - 1);  in insertSetreg()
238 // instruction we get its mode usage. If the instruction uses the Mode register
240 // - update the Change status, which tracks the changes to the Mode register
243 //   of the Mode register we merge the modes
246 //   mode
273       // We preserve any explicit mode register setreg instruction we encounter,  in processBlockPhase1()
290       // not an immediate then we treat the modified bits of the mode register  in processBlockPhase1()
295         unsigned Mode = (Val << Offset) & Mask;  in processBlockPhase1()  local
296         Status Setreg = Status(Mask, Mode);  in processBlockPhase1()
305       // This instruction uses the Mode register and its requirements aren't  in processBlockPhase1()
306       // compatible with the current mode.  in processBlockPhase1()
308         // If the required mode change cannot be included in the current  in processBlockPhase1()
350 // In Phase 2 we revisit each block and calculate the common Mode register
366     // Mask bits (which represent the Mode bits with a known value) can only be  in processBlockPhase2()
416 // check whether the predecessor mode meets the block's entry requirements. If
417 // not we insert an appropriate setreg instruction to modify the Mode register.
448   // a non-default rounding mode for non-strictfp functions. But it should not  in run()
459   // Phase 1 - determine the initial mode required by each block, and add setreg  in run()
464   // Phase 2 - determine the exit mode from each block. We add all blocks to the  in run()
474   // Phase 3 - add an initial setreg to each block where the required entry mode  in run()
475   // is not satisfied by the exit mode of all its predecessors.  in run()