IBM SPEC CPU2000 Flag Descriptions for Opteron Portland Group Compiler Technology's Fortran compiler pgf90 5.0-1 GCC C Compiler version 3.3 Last updated: 15-September-2003 Portability Options -Mfixed (galgel) indicates that source code is in fixed (72 column) format. -DHAS_ERRLIST (Eon) Specify that the programming environment provides a specification for "sys_errlist[]" -DLINUX_i386 (crafty) Specifies that it is a Linux Intel processor-based system which makes the compiler use "long long" as the 64-bit variable that 186.crafty needs -DSPEC_CPU2000_NEED_BOOL (perlbmk) This enables the code changes for use of the SPEC provided definition of the boolean type -DSPEC_CPU2000_LINUX_I386 (perlbmk) This enables the code changes for porting to Linux on i386 architecture to be utilized -DSPEC_CPU2000_LP64 (Portability) Use code to make longs and pointers 64 bit -DSPEC_CPU2000_GLIBC22 (perlbmk) This enables the code changes for compatibility with the 2.2 and later versions of the glibc libraries (also requires use of the src.alt approved for these versions of glibc) -DSYS_HAS_ANSI (gap) -DSYS_HAS_CALLOC_PROTO (gap) -DSYS_HAS_IOCTL_PROTO (gap) -DSYS_HAS_SIGNAL_PROTO (gap) -DSYS_HAS_TIME_PROTO (gap) -DSYS_IS_USG (gap) These defines specify the correct configuration settings for the Linux/GlibC program environment -DFMAX_IS_DOUBLE (eon) Specifies whether FMAX is double or float -finline-limit=n -finline-limit=900 -finline-limit=1000 By default, gcc limits the size of functions that can be inlined. This flag allows the control of this limit for functions that are explicitly marked as inline (i.e., marked with the inline keyword or defined within the class definition in c++). n is the size of functions that can be inlined in number of pseudo instructions (not counting parameter handling). The default value of n is 600. -ffast-math `-ffast-math' Sets `-fno-math-errno', `-funsafe-math-optimizations', `-fno-trapping-math', `-ffinite-math-only' and `-fno-signaling-nans'. This option causes the preprocessor macro `__FAST_MATH__' to be defined. -freduce-all-givs Forces all general-induction variables in loops to be strength-reduced. -funroll-all-loops (GCC Compiler) Unroll all loops, even if their number of iterations is uncertain when the loop is entered. This usually makes programs run more slowly. `-funroll-all-loops' implies the same options as `-funroll-loops' -funroll-loops Unroll loops whose number of iterations can be determined at compile time or upon entry to the loop. -funroll-loops implies both -fstrength-reduce and -frerun-cse-after-loop. This option makes code larger, and may or may not make it run faster. Flags and Compiler options for the Portland Group Compiler Technology's Fortran compiler Fortran pgf90 5.0-1 The optimization levels and their meanings are as follows: -O0 A basic block is generated for each Fortran statement. No scheduling is done between statements. No global optimizations are performed. -O1 Scheduling within extended basic blocks is performed. Some register allocation is performed. No global optimizations are performed. -O2 All level 1 optimizations are performed. In addition, scalar optimizations such as induction recognition and loop invariant motion are performed by the global optimizer. -O3 This level performs all level-one and level-two optimizations and enables more aggressive hoisting and scalar replacement optimizations. -fast Chooses generally optimal flags for the target platform. Equivalent to "-O2 -Munroll -Mnoframe" -fastsse Chooses generally optimal flags for machines that supports the SSE type instructions. Equivalent to "-fast -Mscalarsse -Mvect=sse -Mcache_align -Mflushz" IPA InterProcedural Analyzer -Mcache_align (PGI Fortran Compiler) Align unconstrained objects of length greater than or equal to 16 bytes on cache-line boundaries. An unconstrained object is a data object that is not a member of an aggregate structure or common block. This option does not affect the alignment of allocatable or automatic arrays. Note: To effect cache-line alignment of stack-based local variables, the main program or function must be compiled with -Mcache_align. -Mfixed (PGI Fortran Compiler) Process source using Fortran90 freeform specifications. -Mflushz (PGI Fortran Compiler) Set SSE MXCSR register to flush-to-zero mode. -Mipa=align (PGI Fortran Compiler) Instructs the IPA to recognize when pointer targets are all cache-line aligned, allowing better SSE code generation. -Mipa=arg (PGI Fortran Compiler) Instructs the IPA to remove arguments replaced by -Mipa=ptr,const -Mipa=const (PGI Fortran Compiler) Enable propagation of constants across procedure calls. -Mipa=fast (PGI Fortran Compiler) Equivalent to: -Mipa=const,globals,localarg,ptr,vestigial -Mipa=globals (PGI Fortran Compiler) Instructs the IPA to optimize references to globals when not used in procedure calls. -Mipa=localarg (PGI Fortran Compiler) Externalizes local variables for use with -Mipa=arg -Mipa=ptr (PGI Fortran Compiler) Instructs the IPA to perform pointer disambiguation across procedure calls. -Mipa=vestigial (PGI Fortran Compiler) Instructs the IPA to eliminate functions that are not called. -Mnoframe (PGI Fortran Compiler) Eliminate operations that set up a true stack frame pointer for functions. -Mnosmart (PGI Fortran Compiler) Don't run the Smart assembly re-write tool to enable post-compilation linear assembly scheduling and optimization -Mscalarsse (PGI Fortran Compiler) Utilize the SSE (Streaming SIMD(Single Instruction Multiple Data) Extensions) and SSE2 instructions to perform the operations coded. This assumes the user has an assembler capable of interpreting SSE/SSE2 instructions, as in later versions of Linux. This implies -Mflushz. -Munroll (PGI Fortran Compiler) Invokes the loop unroller. This also sets the optimization level to 2 if the level is set to less than 2. c:m Instructs the compiler to completely unroll loops with a constant loop count less than or equal to m, a supplied constant. If this value is not supplied, the m count is set to 4. n:u Instructs the compiler to unroll u times, a loop which is not completely unrolled, or has a non-constant loop count. If u is not supplied, the unroller computes the number of times a candidate loop is unrolled. -Mvect=sse (PGI Fortran Compiler) Instructs the vectorizer to search for loops, and where possible, use the SSE or SSE2 and prefetch instructions (depending on which processor is targeted). Flags and Compiler options for the GCC 'C' Complier version 3.3 -O0 (GCC C Compiler) Do not optimize. This is the default. -O (GCC C Compiler) -O1 Optimize. Optimizing compilation takes somewhat more time, and a lot more memory for a large function. With `-O', the compiler tries to reduce code size and execution time, without performing any optimizations that take a great deal of compilation time. `-O' turns on the following optimization flags: -fcprop-registers -fcrossjumping -fdefer-pop -fdelayed-branch -fif-conversion -fif-conversion2 -floop-optimize -fmerge-constants -fthread-jumps `-O' also turns on `-fomit-frame-pointer' on machines where doing so does not interfere with debugging. -O2 (GCC C Compiler) Optimize even more. GCC performs nearly all supported optimizations that do not involve a space-speed tradeoff. The compiler does not perform loop unrolling or function inlining when you specify `-O2'. As compared to `-O', this option increases both compilation time and the performance of the generated code. `-O2' turns on all optimization flags specified by `-O'. It also turns on the following optimization flags: -falign-functions -falign-jumps -falign-labels -falign-loops -fcaller-saves -fcse-follow-jumps -fcse-skip-blocks -fdelete-null-pointer-checks -fexpensive-optimizations -fforce-mem -fgcse -fgcse-lm -fgcse-sm -foptimize-sibling-calls -fpeephole2 -fregmove -freorder-blocks -freorder-functions -frerun-cse-after-loop -frerun-loop-opt -fschedule-insns -fschedule-insns2 -fsched-interblock -fsched-spec -fstrength-reduce -fstrict-aliasing Please note the warning under `-fgcse' about invoking `-O2' on programs that use computed gotos. -O3 (GCC C Compiler) Optimize yet more. `-O3' turns on all optimizations specified by `-O2' and also turns on the following: -finline-functions -frename-registers -falign-functions (GCC C Compiler) -falign-functions=N Align the start of functions to the next power-of-two greater than N, skipping up to N bytes. For instance, `-falign-functions=32' aligns functions to the next 32-byte boundary, but `-falign-functions=24' would align to the next 32-byte boundary only if this can be done by skipping 23 bytes or less. `-fno-align-functions' and `-falign-functions=1' are equivalent and mean that functions will not be aligned. Some assemblers only support this flag when N is a power of two; in that case, it is rounded up. If N is not specified, use a machine-dependent default. -falign-jumps (GCC C Compiler) -falign-jumps=N Align branch targets to a power-of-two boundary, for branch targets where the targets can only be reached by jumping, skipping up to N bytes like `-falign-functions'. In this case, no dummy operations need be executed. If N is not specified, use a machine-dependent default. -falign-labels (GCC C Compiler) -falign-labels=N Align all branch targets to a power-of-two boundary, skipping up to N bytes like `-falign-functions'. This option can easily make code slower, because it must insert dummy operations for when the branch target is reached in the usual flow of the code. If `-falign-loops' or `-falign-jumps' are applicable and are greater than this value, then their values are used instead. If N is not specified, use a machine-dependent default which is very likely to be `1', meaning no alignment. -falign-loops (GCC C Compiler) -falign-loops=N Align loops to a power-of-two boundary, skipping up to N bytes like `-falign-functions'. The hope is that the loop will be executed many times, which will makeup for any execution of the dummy operations. If N is not specified, use a machine-dependent default. -fbranch-probabilities (GCC C Compiler) After running a program compiled with -fprofile-arcs, you can compile it a second time using -fbranch-probabilities, to improve optimizations based on the number of times each branch was taken. When the program compiled with -fprofile-arcs exits it saves arc execution counts to a file called sourcename.da for each source file The information in this data file is very dependent on the structure of the generated code, so you must use the same source code and the same optimization options for both compilations. With -fbranch-probabilities, GCC puts a REG_EXEC_COUNT note on the first instruction of each basic block, and a REG_BR_PROB note on each JUMP_INSN and CALL_INSN. These can be used to improve optimization. Currently, they are only used in one place: in reorg.c, instead of guessing which path a branch is mostly to take, the REG_BR_PROB values are used to exactly determine which path is taken more often. -fcaller-saves (GCC C Compiler) Enable values to be allocated in registers that will be clobbered by function calls, by emitting extra instructions to save and restore the registers around such calls. Such allocation is done only when it seems to result in better code than would otherwise be produced. This option is always enabled by default on certain machines, usually those which have no call-preserved registers to use instead. -fcprop-registers (GCC C Compiler) -fno-cprop-registers After register allocation and post-register allocation instruction splitting, we perform a copy-propagation pass to try to reduce scheduling dependencies and occasionally eliminate the copy. -fcrossjumping (GCC C Compiler) Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The resulting code may or may not perform better than without cross-jumping. -fcse-follow-jumps- (GCC C Compiler) In common subexpression elimination, scan through jump instructions when the target of the jump is not reached by any other path. For example, when CSE encounters an `if' statement with an `else' clause, CSE will follow the jump when the condition tested is false. -fcse-skip-blocks (GCC C Compiler) This is similar to `-fcse-follow-jumps', but causes CSE to follow jumps which conditionally skip over blocks. When CSE encounters a simple `if' statement with no else clause, `-fcse-skip-blocks' causes CSE to follow the jump around the body of the `if'. -fdefer-pop (GCC C Compiler) -fno-defer-pop Always pop the arguments to each function call as soon as that function returns. For machines which must pop arguments after a function call, the compiler normally lets arguments accumulate on the stack for several function calls and pops them all at once. -fdelayed-branch (GCC C Compiler) If supported for the target machine, attempt to reorder instructions to exploit instruction slots available after delayed branch instructions. -fdelete-null-pointer-checks (GCC C Compiler) Use global dataflow analysis to identify and eliminate useless checks for null pointers. The compiler assumes that dereferencing a null pointer would have halted the program. If a pointer is checked after it has already been dereferenced, it cannot be null. In some environments, this assumption is not true, and programs can safely dereference null pointers. Use `-fno-delete-null-pointer-checks' to disable this optimization for programs which depend on that behavior. -fexpensive-optimizations (GCC C Compiler) Perform a number of minor optimizations that are relatively expensive. -fforce-mem (GCC C Compiler) Force memory operands to be copied into registers before doing arithmetic on them. This produces better code by making all memory references potential common subexpressions. When they are not common subexpressions, instruction combination should eliminate the separate register-load. -fgcse (GCC C Compiler) Perform a global common subexpression elimination pass. This pass also performs global constant and copy propagation. _Note:_ When compiling a program using computed gotos, a GCC extension, you may get better runtime performance if you disable the global common subexpression elimination pass by adding `-fno-gcse' to the command line. -fgcse-lm (GCC C Compiler) When `-fgcse-lm' is enabled, global common subexpression elimination will attempt to move loads which are only killed by stores into themselves. This allows a loop containing a load/store sequence to be changed to a load outside the loop, and a copy/store within the loop. Enabled by default when gcse is enabled. -fgcse-sm (GCC C Compiler) When `-fgcse-sm' is enabled, A store motion pass is run after global common subexpression elimination. This pass will attempt to move stores out of loops. When used in conjunction with `-fgcse-lm', loops containing a load/store sequence can be changed to a load before the loop and a store after the loop. Enabled by default when gcse is enabled. -fif-conversion (GCC C Compiler) Attempt to transform conditional jumps into branch-less equivalents. This include use of conditional moves, min, max, set flags and abs instructions, and some tricks doable by standard arithmetics. The use of conditional execution on chips where it is available is controlled by `if-conversion2'. -fif-conversion2 (GCC C Compiler) Use conditional execution (where available) to transform conditional jumps into branch-less equivalents. -finline-functions (GCC C Compiler) Integrate all simple functions into their callers. The compiler heuristically decides which functions are simple enough to be worth integrating in this way. If all calls to a given function are integrated, and the function is declared "static", then the function is normally not output as assembler code in its own right. -floop-optimize (GCC C Compiler) Perform loop optimizations: move constant expressions out of loops, simplify exit test conditions and optionally do strength-reduction and loop unrolling as well. -fmerge-constants (GCC C Compiler) Attempt to merge identical constants (string constants and floating point constants) across compilation units. This option is the default for optimized compilation if the assembler and linker support it. Use `-fno-merge-constants' to inhibit this behavior. -fno-guess-branch-probability (GCC C Compiler) Do not guess branch probabilities using a randomized model. Sometimes gcc will opt to use a randomized model to guess branch probabilities, when none are available from either profiling feedback (`-fprofile-arcs') or `__builtin_expect'. This means that different runs of the compiler on the same program may produce different object code. In a hard real-time system, people don't want different runs of the compiler to produce code that has different behavior; minimizing non-determinism is of paramount import. This switch allows users to reduce non-determinism, possibly at the expense of inferior optimization. -fomit-frame-pointer (GCC C Compiler) Don't keep the frame pointer in a register for functions that don't need one. This avoids the instructions to save, set up and restore frame pointers; it also makes an extra register available in many functions. It also makes debugging impossible on some machines. On some machines, such as the VAX, this flag has no effect, because the standard calling sequence automatically handles the frame pointer and nothing is saved by pretending it doesn't exist. The machine-description macro FRAME_POINTER_REQUIRED controls whether a target machine supports this flag. -foptimize-register-move (GCC C Compiler) Attempt to reassign register numbers in move instructions and as operands of other simple instructions in order to maximize the amount of register tying. This is especially helpful on machines with two-operand instructions. -foptimize-sibling-calls (GCC C Compiler) Optimize sibling and tail recursive calls. -fpeephole (GCC C Compiler) -fno-peephole -fpeephole2 (GCC C Compiler) -fno-peephole2 Enable/Disable any machine-specific peephole optimizations. The difference between `-fno-peephole' and `-fno-peephole2' is in how they are implemented in the compiler; some targets use one, some use the other, a few use both. -fprofile-arcs (GCC C Compiler) Instrument arcs during compilation to generate coverage data or for profile-directed block ordering. During execution the program records how many times each branch is executed and how many times it is taken. When the compiled program exits it saves this data to a file called sourcename.da for each source file. For profile-directed block ordering, compile the program with -fprofile-arcs plus optimization and code generation options, generate the arc profile information by running the program on a selected workload, and then compile the program again with the same optimization and code generation options plus -fbranch-probabilities. The other use of -fprofile-arcs is for use with gcov, when it is used with the -ftest-coverage option. With -fprofile-arcs, for each function of your program GCC creates a program flow graph, then finds a spanning tree for the graph. Only arcs that are not on the spanning tree have to be instrumented: the compiler adds code to count the number of times that these arcs are executed. When an arc is the only exit or only entrance to a block, the instrumentation code can be added to the block; otherwise, a new basic block must be created to hold the instrumentation code. -fregmove (GCC C Compiler) Attempt to reassign register numbers in move instructions and as operands of other simple instructions in order to maximize the amount of register tying. This is especially helpful on machines with two-operand instructions. Note `-fregmove' and `-foptimize-register-move' are the same optimization. -frename-registers (GCC C Compiler) Attempt to avoid false dependencies in scheduled code by making use of registers left over after register allocation. This optimization will most benefit pro cessors with lots of registers. It can, however, make debugging impossible, since variables will no longer stay in a ``home register''. -freorder-blocks (GCC C Compiler) Reorder basic blocks in the compiled function in order to reduce number of taken branches and improve code locality. -freorder-functions (GCC C Compiler) Reorder basic blocks in the compiled function in order to reduce number of taken branches and improve code locality. This is implemented by using special subsections `text.hot' for most frequently executed functions and `text.unlikely' for unlikely executed functions. Reordering is done by the linker so object file format must support named sections and linker must place them in a reasonable way. Also profile feedback must be available in to make this option effective. See ` -fprofile-arcs' for details. -frerun-cse-after-loop (GCC C Compiler) Re-run common subexpression elimination after loop optimizations has been performed. -frerun-loop-opt (GCC C Compiler) Run the loop optimizer twice. -fschedule-insns (GCC C Compiler) If supported for the target machine, attempt to reorder instructions to eliminate execution stalls due to required data being unavailable. This helps machines that have slow floating point or memory load instructions by allowing other instructions to be issued until the result of the load or floating point instruction is required. -fschedule-insns2 (GCC C Compiler) Similar to `-fschedule-insns', but requests an additional pass of instruction scheduling after register allocation has been done. This is especially useful on machines with a relatively small number of registers and where memory load instructions take more than one cycle. -fsched-interblock `-fno-sched-interblock' (GCC C Compiler) Don't schedule instructions across basic blocks. This is normally enabled by default when scheduling before register allocation, i.e. with `-fschedule-insns' or at `-O2' or higher. -fsched-spec` -fno-sched-spec' (GCC C Compiler) Don't allow speculative motion of non-load instructions. This is normally enabled by default when scheduling before register allocation, i.e. with `-fschedule-insns' or at `-O2' or higher. -fstrength-reduce (GCC C Compiler) Perform the optimizations of loop strength reduction and elimination of iteration variables. -fstrict-aliasing (GCC C Compiler) Allows the compiler to assume the strictest aliasing rules applicable to the language being compiled. For C (and C++), this activates optimizations based on the type of expressions. In particular, an object of one type is assumed never to reside at the same address as an object of a different type, unless the types are almost the same. For example, an `unsigned int' can alias an `int', but not a `void*' or a `double'. A character type may alias any other type. Pay special attention to code like this: union a_union { int i; double d; }; int f() { a_union t; t.d = 3.0; return t.i; } The practice of reading from a different union member than the one most recently written to (called "type-punning") is common. Even with `-fstrict-aliasing', type-punning is allowed, provided the memory is accessed through the union type. So, the code above will work as expected. However, this code might not: int f() { a_union t; int* ip; t.d = 3.0; ip = &t.i; return *ip; } Every language that wishes to perform language-specific alias analysis should define a function that computes, given an `tree' node, an alias set for the node. Nodes in different alias sets are not allowed to alias. For an example, see the C front-end function `c_get_alias_set'. -fthread-jumps (GCC C Compiler) Perform optimizations where we check to see if a jump branches to a location where another comparison subsumed by the first is found. If so, the first branch is redirected to either the destination of the second branch or a point immediately following it, depending on whether the condition is known to be true or false. -m32 (GCC Compiler) The `-m' switches are supported on AMD x86-64 processors in 64-bit environments. `-m32' `-m64' Generate code for a 32-bit or 64-bit environment. The 32-bit environment sets int, long and pointer to 32 bits and generates code that runs on any i386 system. The 64-bit environment sets int to 32 bits and long and pointer to 64 bits and generates code for AMD's x86-64 architecture. -static (GCC C Compiler) This prevents linking with the shared libraries. rm -f *.da *.life analyz_prbrob.out Remove any profile feedback information from previous runs. BIOS Setting Definitions - DRAM Interleave defines whether data will be interleaved among the four data banks within individual DRAMs. Node Interleave defines whether or not data addresses will be alternating between both processors in 4KB blocks. ACPI SRAT defines whether the Static Resource Allocation Table is exported by the BIOS to a location where the operating system can see it. The SRAT may only be exported when Node Interleave is disabled.