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[X86] AMD Zen 3: same-reg AVX XMM VXORPS is a zero-cycle(!) dep-breaking zero-idiom 

Unlike it's legacy SSE XMM XORPS version, which measures as being 1-cycle,
this one is certainly a zero-cycle instruction, in addition to both of them
being dependency breaking.

As confirmed by exegesis measurements, and ref docs.
This commit is contained in:
Roman Lebedev 2021-05-14 11:06:39 +03:00
parent a9fb321a67
commit 26c1bffe67
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GPG Key ID: 083C3EBB4A1689E0
2 changed files with 30 additions and 20 deletions
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10
llvm/lib/Target/X86/X86ScheduleZnver3.td
View File

@ -1530,6 +1530,13 @@ def : InstRW<[Zn3WriteZeroIdiomEFLAGS], (instrs CMP8rr, CMP8rr_REV,
CMP32rr, CMP32rr_REV,
CMP64rr, CMP64rr_REV)>;
def Zn3WriteFZeroIdiom : SchedWriteVariant<[
SchedVar<MCSchedPredicate<ZeroIdiomPredicate>, [Zn3WriteZeroLatency]>,
SchedVar<NoSchedPred, [WriteFLogic]>
]>;
// NOTE: XORPSrr is not zero-cycle!
def : InstRW<[Zn3WriteFZeroIdiom], (instrs VXORPSrr)>;
def : IsZeroIdiomFunction<[
// GPR Zero-idioms.
DepBreakingClass<[ XOR32rr, XOR32rr_REV,
@ -1539,6 +1546,9 @@ def : IsZeroIdiomFunction<[
// SSE XMM Zero-idioms.
DepBreakingClass<[ XORPSrr ], ZeroIdiomPredicate>,
// AVX XMM Zero-idioms.
DepBreakingClass<[ VXORPSrr ], ZeroIdiomPredicate>,
]>;
def : IsDepBreakingFunction<[

40
llvm/test/tools/llvm-mca/X86/Znver3/zero-idioms-avx-xmm.s
View File

@ -10,13 +10,13 @@ vxorps %xmm1, %xmm0, %xmm0
# CHECK: Iterations: 10000
# CHECK-NEXT: Instructions: 20000
# CHECK-NEXT: Total Cycles: 20003
# CHECK-NEXT: Total Cycles: 3337
# CHECK-NEXT: Total uOps: 20000
# CHECK: Dispatch Width: 6
# CHECK-NEXT: uOps Per Cycle: 1.00
# CHECK-NEXT: IPC: 1.00
# CHECK-NEXT: Block RThroughput: 0.5
# CHECK-NEXT: uOps Per Cycle: 5.99
# CHECK-NEXT: IPC: 5.99
# CHECK-NEXT: Block RThroughput: 0.3
# CHECK: Instruction Info:
# CHECK-NEXT: [1]: #uOps
@ -27,17 +27,17 @@ vxorps %xmm1, %xmm0, %xmm0
# CHECK-NEXT: [6]: HasSideEffects (U)
# CHECK: [1] [2] [3] [4] [5] [6] Instructions:
# CHECK-NEXT: 1 1 0.25 vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: 1 0 0.17 vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: 1 1 0.25 vxorps %xmm1, %xmm0, %xmm0
# CHECK: Register File statistics:
# CHECK-NEXT: Total number of mappings created: 20000
# CHECK-NEXT: Max number of mappings used: 66
# CHECK-NEXT: Total number of mappings created: 10000
# CHECK-NEXT: Max number of mappings used: 9
# CHECK: * Register File #1 -- Zn3FpPRF:
# CHECK-NEXT: Number of physical registers: 160
# CHECK-NEXT: Total number of mappings created: 20000
# CHECK-NEXT: Max number of mappings used: 66
# CHECK-NEXT: Total number of mappings created: 10000
# CHECK-NEXT: Max number of mappings used: 9
# CHECK: * Register File #2 -- Zn3IntegerPRF:
# CHECK-NEXT: Number of physical registers: 192
@ -71,20 +71,20 @@ vxorps %xmm1, %xmm0, %xmm0
# CHECK: Resource pressure per iteration:
# CHECK-NEXT: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12.0] [12.1] [13] [14.0] [14.1] [14.2] [15.0] [15.1] [15.2] [16.0] [16.1]
# CHECK-NEXT: - - - - - - - - 0.50 0.50 0.50 0.50 - - - - - - - - - - -
# CHECK-NEXT: - - - - - - - - 0.25 0.25 0.25 0.25 - - - - - - - - - - -
# CHECK: Resource pressure by instruction:
# CHECK-NEXT: [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12.0] [12.1] [13] [14.0] [14.1] [14.2] [15.0] [15.1] [15.2] [16.0] [16.1] Instructions:
# CHECK-NEXT: - - - - - - - - - 0.50 - 0.50 - - - - - - - - - - - vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: - - - - - - - - 0.50 - 0.50 - - - - - - - - - - - - vxorps %xmm1, %xmm0, %xmm0
# CHECK-NEXT: - - - - - - - - - - - - - - - - - - - - - - - vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: - - - - - - - - 0.25 0.25 0.25 0.25 - - - - - - - - - - - vxorps %xmm1, %xmm0, %xmm0
# CHECK: Timeline view:
# CHECK-NEXT: Index 0123456
# CHECK-NEXT: Index 0123
# CHECK: [0,0] DeER .. vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: [0,1] D=eER.. vxorps %xmm1, %xmm0, %xmm0
# CHECK-NEXT: [1,0] D==eER. vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: [1,1] D===eER vxorps %xmm1, %xmm0, %xmm0
# CHECK: [0,0] DR . vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: [0,1] DeER vxorps %xmm1, %xmm0, %xmm0
# CHECK-NEXT: [1,0] D--R vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: [1,1] DeER vxorps %xmm1, %xmm0, %xmm0
# CHECK: Average Wait times (based on the timeline view):
# CHECK-NEXT: [0]: Executions
@ -93,6 +93,6 @@ vxorps %xmm1, %xmm0, %xmm0
# CHECK-NEXT: [3]: Average time elapsed from WB until retire stage
# CHECK: [0] [1] [2] [3]
# CHECK-NEXT: 0. 2 2.0 0.5 0.0 vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: 1. 2 3.0 0.0 0.0 vxorps %xmm1, %xmm0, %xmm0
# CHECK-NEXT: 2 2.5 0.3 0.0 <total>
# CHECK-NEXT: 0. 2 0.0 0.0 1.0 vxorps %xmm0, %xmm0, %xmm0
# CHECK-NEXT: 1. 2 1.0 1.0 0.0 vxorps %xmm1, %xmm0, %xmm0
# CHECK-NEXT: 2 0.5 0.5 0.5 <total>