On Jaguar, CMPXCHG has a latency of 11cy, and a maximum throughput of 0.33 IPC.
Throughput is superiorly limited to 0.33 because of the implicit in/out
dependency on register EAX. In the case of repeated non-atomic CMPXCHG with the
same memory location, store-to-load forwarding occurs and values for sequent
loads are quickly forwarded from the store buffer.
Interestingly, the functionality in LLVM that computes the reciprocal throughput
doesn't seem to know about RMW instructions. That functionality only looks at
the "consumed resource cycles" for the throughput computation. It should be
fixed/improved by a future patch. In particular, for RMW instructions, that
logic should also take into account for the write latency of in/out register
operands.
An atomic CMPXCHG has a latency of ~17cy. Throughput is also limited to
~17cy/inst due to cache locking, which prevents other memory uOPs to start
executing before the "lock releasing" store uOP.
CMPXCHG8rr and CMPXCHG8rm are treated specially because they decode to one less
macro opcode. Their latency tend to be the same as the other RR/RM variants. RR
variants are relatively fast 3cy (but still microcoded - 5 macro opcodes).
CMPXCHG8B is 11cy and unfortunately doesn't seem to benefit from store-to-load
forwarding. That means, throughput is clearly limited by the in/out dependency
on GPR registers. The uOP composition is sadly unknown (due to the lack of PMCs
for the Integer pipes). I have reused the same mix of consumed resource from the
other CMPXCHG instructions for CMPXCHG8B too.
LOCK CMPXCHG8B is instead 18cycles.
CMPXCHG16B is 32cycles. Up to 38cycles when the LOCK prefix is specified. Due to
the in/out dependencies, throughput is limited to 1 instruction every 32 (or 38)
cycles dependeing on whether the LOCK prefix is specified or not.
I wouldn't be surprised if the microcode for CMPXCHG16B is similar to 2x
microcode from CMPXCHG8B. So, I have speculatively set the JALU01 consumption to
2x the resource cycles used for CMPXCHG8B.
The two new hasLockPrefix() functions are used by the btver2 scheduling model
check if a MCInst/MachineInst has a LOCK prefix. Calls to hasLockPrefix() have
been encoded in predicates of variant scheduling classes that describe lat/thr
of CMPXCHG.
Differential Revision: https://reviews.llvm.org/D66424
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@369365
91177308-0d34-0410-b5e6-
96231b3b80d8
return DWARFFlavour::X86_32_Generic;
}
+bool X86_MC::hasLockPrefix(const MCInst &MI) {
+ return MI.getFlags() & X86::IP_HAS_LOCK;
+}
+
void X86_MC::initLLVMToSEHAndCVRegMapping(MCRegisterInfo *MRI) {
// FIXME: TableGen these.
for (unsigned Reg = X86::NoRegister + 1; Reg < X86::NUM_TARGET_REGS; ++Reg) {
void initLLVMToSEHAndCVRegMapping(MCRegisterInfo *MRI);
+
+/// Returns true if this instruction has a LOCK prefix.
+bool hasLockPrefix(const MCInst &MI);
+
/// Create a X86 MCSubtargetInfo instance. This is exposed so Asm parser, etc.
/// do not need to go through TargetRegistry.
MCSubtargetInfo *createX86MCSubtargetInfo(const Triple &TT, StringRef CPU,
#define GET_INSTRINFO_HELPER_DECLS
#include "X86GenInstrInfo.inc"
+ static bool hasLockPrefix(const MachineInstr &MI) {
+ return MI.getDesc().TSFlags & X86II::LOCK;
+ }
+
Optional<ParamLoadedValue>
describeLoadedValue(const MachineInstr &MI) const override;
CheckImmOperand_s<5, "X86::COND_A">,
CheckImmOperand_s<5, "X86::COND_BE">
]>;
+
+// A predicate used to check if an instruction has a LOCK prefix.
+def CheckLockPrefix : CheckFunctionPredicate<
+ "X86_MC::hasLockPrefix",
+ "X86InstrInfo::hasLockPrefix"
+>;
+
+def IsRegRegCompareAndSwap_8 : CheckOpcode<[ CMPXCHG8rr ]>;
+
+def IsRegMemCompareAndSwap_8 : CheckOpcode<[
+ LCMPXCHG8, CMPXCHG8rm
+]>;
+
+def IsRegRegCompareAndSwap_16_32_64 : CheckOpcode<[
+ CMPXCHG16rr, CMPXCHG32rr, CMPXCHG64rr
+]>;
+
+def IsRegMemCompareAndSwap_16_32_64 : CheckOpcode<[
+ CMPXCHG16rm, CMPXCHG32rm, CMPXCHG64rm,
+ LCMPXCHG16, LCMPXCHG32, LCMPXCHG64,
+ LCMPXCHG8B, LCMPXCHG16B
+]>;
+
+def IsCompareAndSwap8B : CheckOpcode<[ CMPXCHG8B, LCMPXCHG8B ]>;
+def IsCompareAndSwap16B : CheckOpcode<[ CMPXCHG16B, LCMPXCHG16B ]>;
+
+def IsRegMemCompareAndSwap : CheckOpcode<
+ !listconcat(
+ IsRegMemCompareAndSwap_8.ValidOpcodes,
+ IsRegMemCompareAndSwap_16_32_64.ValidOpcodes
+ )>;
+
+def IsRegRegCompareAndSwap : CheckOpcode<
+ !listconcat(
+ IsRegRegCompareAndSwap_8.ValidOpcodes,
+ IsRegRegCompareAndSwap_16_32_64.ValidOpcodes
+ )>;
+
+def IsAtomicCompareAndSwap_8 : CheckAll<[
+ CheckLockPrefix,
+ IsRegMemCompareAndSwap_8
+]>;
+
+def IsAtomicCompareAndSwap : CheckAll<[
+ CheckLockPrefix,
+ IsRegMemCompareAndSwap
+]>;
+
+def IsAtomicCompareAndSwap8B : CheckAll<[
+ CheckLockPrefix,
+ IsCompareAndSwap8B
+]>;
+
+def IsAtomicCompareAndSwap16B : CheckAll<[
+ CheckLockPrefix,
+ IsCompareAndSwap16B
+]>;
defm : JWriteResIntPair<WriteALU, [JALU01], 1>;
defm : JWriteResIntPair<WriteADC, [JALU01], 1, [2]>;
-defm : X86WriteRes<WriteBSWAP32, [JALU01], 1, [1], 1>;
-defm : X86WriteRes<WriteBSWAP64, [JALU01], 1, [1], 1>;
-defm : X86WriteRes<WriteCMPXCHG,[JALU01], 1, [1], 1>;
-defm : X86WriteRes<WriteCMPXCHGRMW,[JALU01, JSAGU, JLAGU], 4, [1, 1, 1], 2>;
+defm : X86WriteRes<WriteBSWAP32, [JALU01], 1, [1], 1>;
+defm : X86WriteRes<WriteBSWAP64, [JALU01], 1, [1], 1>;
+defm : X86WriteRes<WriteCMPXCHG, [JALU01], 3, [3], 5>;
+defm : X86WriteRes<WriteCMPXCHGRMW, [JALU01, JSAGU, JLAGU], 11, [3, 1, 1], 6>;
defm : X86WriteRes<WriteXCHG, [JALU01], 1, [1], 1>;
defm : JWriteResIntPair<WriteIMul8, [JALU1, JMul], 3, [1, 1], 2>;
// to '1' to tell the scheduler that the nop uses an ALU slot for a cycle.
def : WriteRes<WriteNop, [JALU01]> { let Latency = 1; }
+def JWriteCMPXCHG8rr : SchedWriteRes<[JALU01]> {
+ let Latency = 3;
+ let ResourceCycles = [3];
+ let NumMicroOps = 3;
+}
+
+def JWriteLOCK_CMPXCHG8rm : SchedWriteRes<[JALU01, JLAGU, JSAGU]> {
+ let Latency = 16;
+ let ResourceCycles = [3,16,16];
+ let NumMicroOps = 5;
+}
+
+def JWriteLOCK_CMPXCHGrm : SchedWriteRes<[JALU01, JLAGU, JSAGU]> {
+ let Latency = 17;
+ let ResourceCycles = [3,17,17];
+ let NumMicroOps = 6;
+}
+
+def JWriteCMPXCHG8rm : SchedWriteRes<[JALU01, JLAGU, JSAGU]> {
+ let Latency = 11;
+ let ResourceCycles = [3,1,1];
+ let NumMicroOps = 5;
+}
+
+def JWriteCMPXCHG8B : SchedWriteRes<[JALU01, JLAGU, JSAGU]> {
+ let Latency = 11;
+ let ResourceCycles = [3,1,1];
+ let NumMicroOps = 18;
+}
+
+def JWriteCMPXCHG16B : SchedWriteRes<[JALU01, JLAGU, JSAGU]> {
+ let Latency = 32;
+ let ResourceCycles = [6,1,1];
+ let NumMicroOps = 28;
+}
+
+def JWriteLOCK_CMPXCHG8B : SchedWriteRes<[JALU01, JLAGU, JSAGU]> {
+ let Latency = 19;
+ let ResourceCycles = [3,19,19];
+ let NumMicroOps = 18;
+}
+
+def JWriteLOCK_CMPXCHG16B : SchedWriteRes<[JALU01, JLAGU, JSAGU]> {
+ let Latency = 38;
+ let ResourceCycles = [6,38,38];
+ let NumMicroOps = 28;
+}
+
+def JWriteCMPXCHGVariant : SchedWriteVariant<[
+ SchedVar<MCSchedPredicate<IsAtomicCompareAndSwap8B>, [JWriteLOCK_CMPXCHG8B]>,
+ SchedVar<MCSchedPredicate<IsAtomicCompareAndSwap16B>, [JWriteLOCK_CMPXCHG16B]>,
+ SchedVar<MCSchedPredicate<IsAtomicCompareAndSwap_8>, [JWriteLOCK_CMPXCHG8rm]>,
+ SchedVar<MCSchedPredicate<IsAtomicCompareAndSwap>, [JWriteLOCK_CMPXCHGrm]>,
+ SchedVar<MCSchedPredicate<IsCompareAndSwap8B>, [JWriteCMPXCHG8B]>,
+ SchedVar<MCSchedPredicate<IsCompareAndSwap16B>, [JWriteCMPXCHG16B]>,
+ SchedVar<MCSchedPredicate<IsRegMemCompareAndSwap_8>, [JWriteCMPXCHG8rm]>,
+ SchedVar<MCSchedPredicate<IsRegMemCompareAndSwap>, [WriteCMPXCHGRMW]>,
+ SchedVar<MCSchedPredicate<IsRegRegCompareAndSwap_8>, [JWriteCMPXCHG8rr]>,
+ SchedVar<NoSchedPred, [WriteCMPXCHG]>
+]>;
+def : InstRW<[JWriteCMPXCHGVariant], (instrs CMPXCHG8rr, LCMPXCHG8, CMPXCHG8rm,
+ CMPXCHG16rm, CMPXCHG32rm, CMPXCHG64rm,
+ LCMPXCHG16, LCMPXCHG32, LCMPXCHG64,
+ CMPXCHG8B, CMPXCHG16B,
+ LCMPXCHG8B, LCMPXCHG16B)>;
+
+
////////////////////////////////////////////////////////////////////////////////
// Floating point. This covers both scalar and vector operations.
////////////////////////////////////////////////////////////////////////////////
# CHECK-NEXT: [6]: HasSideEffects (U)
# CHECK: [1] [2] [3] [4] [5] [6] Instructions:
-# CHECK-NEXT: 2 4 1.00 * * cmpxchg8b (%rax)
-# CHECK-NEXT: 2 4 1.00 * * cmpxchg16b (%rax)
-# CHECK-NEXT: 2 4 1.00 * * lock cmpxchg8b (%rax)
-# CHECK-NEXT: 2 4 1.00 * * lock cmpxchg16b (%rax)
+# CHECK-NEXT: 18 11 1.50 * * cmpxchg8b (%rax)
+# CHECK-NEXT: 28 32 3.00 * * cmpxchg16b (%rax)
+# CHECK-NEXT: 18 19 19.00 * * lock cmpxchg8b (%rax)
+# CHECK-NEXT: 28 38 38.00 * * lock cmpxchg16b (%rax)
# CHECK: Resources:
# CHECK-NEXT: [0] - JALU0
# CHECK: Resource pressure per iteration:
# CHECK-NEXT: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
-# CHECK-NEXT: 2.00 2.00 - - - - - 4.00 - 4.00 - - - -
+# CHECK-NEXT: 9.00 9.00 - - - - - 59.00 - 59.00 - - - -
# CHECK: Resource pressure by instruction:
# CHECK-NEXT: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] Instructions:
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - cmpxchg8b (%rax)
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - cmpxchg16b (%rax)
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - lock cmpxchg8b (%rax)
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - lock cmpxchg16b (%rax)
+# CHECK-NEXT: 1.50 1.50 - - - - - 1.00 - 1.00 - - - - cmpxchg8b (%rax)
+# CHECK-NEXT: 3.00 3.00 - - - - - 1.00 - 1.00 - - - - cmpxchg16b (%rax)
+# CHECK-NEXT: 1.50 1.50 - - - - - 19.00 - 19.00 - - - - lock cmpxchg8b (%rax)
+# CHECK-NEXT: 3.00 3.00 - - - - - 38.00 - 38.00 - - - - lock cmpxchg16b (%rax)
# CHECK-NEXT: 1 100 0.50 U cmpsw %es:(%rdi), (%rsi)
# CHECK-NEXT: 1 100 0.50 U cmpsl %es:(%rdi), (%rsi)
# CHECK-NEXT: 1 100 0.50 U cmpsq %es:(%rdi), (%rsi)
-# CHECK-NEXT: 1 1 0.50 cmpxchgb %cl, %bl
-# CHECK-NEXT: 2 4 1.00 * * cmpxchgb %cl, (%rbx)
-# CHECK-NEXT: 2 4 1.00 * * lock cmpxchgb %cl, (%rbx)
-# CHECK-NEXT: 1 1 0.50 cmpxchgw %cx, %bx
-# CHECK-NEXT: 2 4 1.00 * * cmpxchgw %cx, (%rbx)
-# CHECK-NEXT: 2 4 1.00 * * lock cmpxchgw %cx, (%rbx)
-# CHECK-NEXT: 1 1 0.50 cmpxchgl %ecx, %ebx
-# CHECK-NEXT: 2 4 1.00 * * cmpxchgl %ecx, (%rbx)
-# CHECK-NEXT: 2 4 1.00 * * lock cmpxchgl %ecx, (%rbx)
-# CHECK-NEXT: 1 1 0.50 cmpxchgq %rcx, %rbx
-# CHECK-NEXT: 2 4 1.00 * * cmpxchgq %rcx, (%rbx)
-# CHECK-NEXT: 2 4 1.00 * * lock cmpxchgq %rcx, (%rbx)
+# CHECK-NEXT: 3 3 1.50 cmpxchgb %cl, %bl
+# CHECK-NEXT: 5 11 1.50 * * cmpxchgb %cl, (%rbx)
+# CHECK-NEXT: 5 16 16.00 * * lock cmpxchgb %cl, (%rbx)
+# CHECK-NEXT: 5 3 1.50 cmpxchgw %cx, %bx
+# CHECK-NEXT: 6 11 1.50 * * cmpxchgw %cx, (%rbx)
+# CHECK-NEXT: 6 17 17.00 * * lock cmpxchgw %cx, (%rbx)
+# CHECK-NEXT: 5 3 1.50 cmpxchgl %ecx, %ebx
+# CHECK-NEXT: 6 11 1.50 * * cmpxchgl %ecx, (%rbx)
+# CHECK-NEXT: 6 17 17.00 * * lock cmpxchgl %ecx, (%rbx)
+# CHECK-NEXT: 5 3 1.50 cmpxchgq %rcx, %rbx
+# CHECK-NEXT: 6 11 1.50 * * cmpxchgq %rcx, (%rbx)
+# CHECK-NEXT: 6 17 17.00 * * lock cmpxchgq %rcx, (%rbx)
# CHECK-NEXT: 1 100 0.50 U cpuid
# CHECK-NEXT: 1 1 0.50 decb %dil
# CHECK-NEXT: 1 5 1.00 * * decb (%rax)
# CHECK: Resource pressure per iteration:
# CHECK-NEXT: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
-# CHECK-NEXT: 612.00 662.00 380.00 - - - - 334.00 64.00 235.00 - - - -
+# CHECK-NEXT: 624.00 674.00 380.00 - - - - 397.00 64.00 298.00 - - - -
# CHECK: Resource pressure by instruction:
# CHECK-NEXT: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] Instructions:
# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - cmpsw %es:(%rdi), (%rsi)
# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - cmpsl %es:(%rdi), (%rsi)
# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - cmpsq %es:(%rdi), (%rsi)
-# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - cmpxchgb %cl, %bl
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - cmpxchgb %cl, (%rbx)
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - lock cmpxchgb %cl, (%rbx)
-# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - cmpxchgw %cx, %bx
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - cmpxchgw %cx, (%rbx)
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - lock cmpxchgw %cx, (%rbx)
-# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - cmpxchgl %ecx, %ebx
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - cmpxchgl %ecx, (%rbx)
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - lock cmpxchgl %ecx, (%rbx)
-# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - cmpxchgq %rcx, %rbx
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - cmpxchgq %rcx, (%rbx)
-# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - lock cmpxchgq %rcx, (%rbx)
+# CHECK-NEXT: 1.50 1.50 - - - - - - - - - - - - cmpxchgb %cl, %bl
+# CHECK-NEXT: 1.50 1.50 - - - - - 1.00 - 1.00 - - - - cmpxchgb %cl, (%rbx)
+# CHECK-NEXT: 1.50 1.50 - - - - - 16.00 - 16.00 - - - - lock cmpxchgb %cl, (%rbx)
+# CHECK-NEXT: 1.50 1.50 - - - - - - - - - - - - cmpxchgw %cx, %bx
+# CHECK-NEXT: 1.50 1.50 - - - - - 1.00 - 1.00 - - - - cmpxchgw %cx, (%rbx)
+# CHECK-NEXT: 1.50 1.50 - - - - - 17.00 - 17.00 - - - - lock cmpxchgw %cx, (%rbx)
+# CHECK-NEXT: 1.50 1.50 - - - - - - - - - - - - cmpxchgl %ecx, %ebx
+# CHECK-NEXT: 1.50 1.50 - - - - - 1.00 - 1.00 - - - - cmpxchgl %ecx, (%rbx)
+# CHECK-NEXT: 1.50 1.50 - - - - - 17.00 - 17.00 - - - - lock cmpxchgl %ecx, (%rbx)
+# CHECK-NEXT: 1.50 1.50 - - - - - - - - - - - - cmpxchgq %rcx, %rbx
+# CHECK-NEXT: 1.50 1.50 - - - - - 1.00 - 1.00 - - - - cmpxchgq %rcx, (%rbx)
+# CHECK-NEXT: 1.50 1.50 - - - - - 17.00 - 17.00 - - - - lock cmpxchgq %rcx, (%rbx)
# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - cpuid
# CHECK-NEXT: 0.50 0.50 - - - - - - - - - - - - decb %dil
# CHECK-NEXT: 0.50 0.50 - - - - - 1.00 - 1.00 - - - - decb (%rax)
projects / llvm / commitdiff