1 //===-- SystemZLongBranch.cpp - Branch lengthening for SystemZ ------------===//
12 // to be in range with a longer form (branch relaxation).  A simple
16 // quadratic in the number of blocks; relaxing branch N can make branch N-1
17 // go out of range, which in turn can make branch N-2 go out of range,
23 // in range (branch shortening).  This too can be implemented as a function
26 // shortening is also quadratic in the worst case; shortening branch N
27 // can bring branch N-1 in range of the short form, which in turn can do
28 // the same for branch N-2, and so on.  The main advantage of shortening
35 // which are relatively rare to begin with, and the long branch sequences
73 #define DEBUG_TYPE "systemz-long-branch"
100   // If this terminator is a relaxable branch, this points to the branch
102   MachineInstr *Branch = nullptr;  member
110   // If Branch is nonnull, this is the number of the target block,
114   // If Branch is nonnull, this is the length of the longest relaxed form,
176 INITIALIZE_PASS(SystemZLongBranch, DEBUG_TYPE, "SystemZ Long Branch", false,
272       llvm_unreachable("Unrecognized branch instruction");  in describeTerminator()
274     Terminator.Branch = &MI;  in describeTerminator()
330   if (!Terminator.Branch || Terminator.ExtraRelaxSize == 0)  in mustRelaxBranch()
368 // Split BRANCH ON COUNT MI into the addition given by AddOpcode followed
405 // Relax the branch described by Terminator.
407   MachineInstr *Branch = Terminator.Branch;  in relaxBranch()  local
408   switch (Branch->getOpcode()) {  in relaxBranch()
410     Branch->setDesc(TII->get(SystemZ::JG));  in relaxBranch()
413     Branch->setDesc(TII->get(SystemZ::BRCL));  in relaxBranch()
416     splitBranchOnCount(Branch, SystemZ::AHI);  in relaxBranch()
419     splitBranchOnCount(Branch, SystemZ::AGHI);  in relaxBranch()
422     splitCompareBranch(Branch, SystemZ::CR);  in relaxBranch()
425     splitCompareBranch(Branch, SystemZ::CGR);  in relaxBranch()
428     splitCompareBranch(Branch, SystemZ::CHI);  in relaxBranch()
431     splitCompareBranch(Branch, SystemZ::CGHI);  in relaxBranch()
434     splitCompareBranch(Branch, SystemZ::CLR);  in relaxBranch()
437     splitCompareBranch(Branch, SystemZ::CLGR);  in relaxBranch()
440     splitCompareBranch(Branch, SystemZ::CLFI);  in relaxBranch()
443     splitCompareBranch(Branch, SystemZ::CLGFI);  in relaxBranch()
446     llvm_unreachable("Unrecognized branch");  in relaxBranch()
451   Terminator.Branch = nullptr;  in relaxBranch()