the processor keeps a return addresses stack (RAS) which stores the address
and the instruction execution state of the instruction after a function-call
type branch instruction.
Calling a "noreturn" function with normal call instructions (e.g. bl) can
corrupt RAS and causes 100% return misprediction so LLVM should use a
unconditional branch instead. i.e.
mov lr, pc
b _foo
The "mov lr, pc" is issued in order to get proper backtrace.
rdar://8979299
llvm-svn: 151623
Moving toward a uniform style of pass definition to allow easier target configuration.
Globally declare Pass ID.
Globally declare pass initializer.
Use INITIALIZE_PASS consistently.
Add a call to the initializer from CodeGen.cpp.
Remove redundant "createPass" functions and "getPassName" methods.
While cleaning up declarations, cleaned up comments (sorry for large diff).
llvm-svn: 150100
Creating the isPredicated TSFlag enables the code
to use the property defined in the instruction format
instead of using a large switch statement.
llvm-svn: 150078
Passes prior to instructon selection are now split into separate configurable stages.
Header dependencies are simplified.
The bulk of this diff is simply removal of the silly DisableVerify flags.
Sorry for the target header churn. Attempting to stabilize them.
llvm-svn: 149754
Allows command line overrides to be centralized in LLVMTargetMachine.cpp.
LLVMTargetMachine can intercept common passes and give precedence to command line overrides.
Allows adding "internal" target configuration options without touching TargetOptions.
Encapsulates the PassManager.
Provides a good point to initialize all CodeGen passes so that Pass ID's can be used in APIs.
Allows modifying the target configuration hooks without rebuilding the world.
llvm-svn: 149672
This new scheduler plugs into the existing selection DAG scheduling framework. It is a top-down critical path scheduler that tracks register pressure and uses a DFA for pipeline modeling.
Patch by Sergei Larin!
llvm-svn: 149547
When set, this bit indicates that a register is completely defined by
the value of its sub-registers.
Use the CoveredBySubRegs property to infer which super-registers are
call-preserved given a list of callee-saved registers. For example, the
ARM registers D8-D15 are callee-saved. This now automatically implies
that Q4-Q7 are call-preserved.
Conversely, Win64 callees save XMM6-XMM15, but the corresponding
YMM6-YMM15 registers are not call-preserved because they are not fully
defined by their sub-registers.
llvm-svn: 148363
NAKAMURA Takumi