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[X86] AMD Zen 3: same-reg AVX YMM VXORPS is a zero-cycle(!) dep-break…
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…ing zero-idiom

As confirmed by exegesis, and ref docs.
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@LebedevRI
LebedevRI committed May 14, 2021
1 parent 2a7c52f commit 59554c0
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Showing 2 changed files with 29 additions and 20 deletions.
9 changes: 9 additions & 0 deletions llvm/lib/Target/X86/X86ScheduleZnver3.td
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Original file line number Diff line number Diff line change
Expand Up @@ -1537,6 +1537,12 @@ def Zn3WriteFZeroIdiom : SchedWriteVariant<[
// NOTE: XORPSrr is not zero-cycle!
def : InstRW<[Zn3WriteFZeroIdiom], (instrs VXORPSrr)>;

def Zn3WriteFZeroIdiomY : SchedWriteVariant<[
SchedVar<MCSchedPredicate<ZeroIdiomPredicate>, [Zn3WriteZeroLatency]>,
SchedVar<NoSchedPred, [WriteFLogicY]>
]>;
def : InstRW<[Zn3WriteFZeroIdiomY], (instrs VXORPSYrr)>;

def : IsZeroIdiomFunction<[
// GPR Zero-idioms.
DepBreakingClass<[ XOR32rr, XOR32rr_REV,
Expand All @@ -1549,6 +1555,9 @@ def : IsZeroIdiomFunction<[

// AVX XMM Zero-idioms.
DepBreakingClass<[ VXORPSrr ], ZeroIdiomPredicate>,

// AVX YMM Zero-idioms.
DepBreakingClass<[ VXORPSYrr ], ZeroIdiomPredicate>,
]>;

def : IsDepBreakingFunction<[
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40 changes: 20 additions & 20 deletions llvm/test/tools/llvm-mca/X86/Znver3/zero-idioms-avx-ymm.s
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Original file line number Diff line number Diff line change
Expand Up @@ -10,13 +10,13 @@ vxorps %ymm1, %ymm0, %ymm0

# 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
Expand All @@ -27,17 +27,17 @@ vxorps %ymm1, %ymm0, %ymm0
# CHECK-NEXT: [6]: HasSideEffects (U)

# CHECK: [1] [2] [3] [4] [5] [6] Instructions:
# CHECK-NEXT: 1 1 0.25 vxorps %ymm0, %ymm0, %ymm0
# CHECK-NEXT: 1 0 0.17 vxorps %ymm0, %ymm0, %ymm0
# CHECK-NEXT: 1 1 0.25 vxorps %ymm1, %ymm0, %ymm0

# 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
Expand Down Expand Up @@ -71,20 +71,20 @@ vxorps %ymm1, %ymm0, %ymm0

# 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 %ymm0, %ymm0, %ymm0
# CHECK-NEXT: - - - - - - - - 0.50 - 0.50 - - - - - - - - - - - - vxorps %ymm1, %ymm0, %ymm0
# CHECK-NEXT: - - - - - - - - - - - - - - - - - - - - - - - vxorps %ymm0, %ymm0, %ymm0
# CHECK-NEXT: - - - - - - - - 0.25 0.25 0.25 0.25 - - - - - - - - - - - vxorps %ymm1, %ymm0, %ymm0

# CHECK: Timeline view:
# CHECK-NEXT: Index 0123456
# CHECK-NEXT: Index 0123

# CHECK: [0,0] DeER .. vxorps %ymm0, %ymm0, %ymm0
# CHECK-NEXT: [0,1] D=eER.. vxorps %ymm1, %ymm0, %ymm0
# CHECK-NEXT: [1,0] D==eER. vxorps %ymm0, %ymm0, %ymm0
# CHECK-NEXT: [1,1] D===eER vxorps %ymm1, %ymm0, %ymm0
# CHECK: [0,0] DR . vxorps %ymm0, %ymm0, %ymm0
# CHECK-NEXT: [0,1] DeER vxorps %ymm1, %ymm0, %ymm0
# CHECK-NEXT: [1,0] D--R vxorps %ymm0, %ymm0, %ymm0
# CHECK-NEXT: [1,1] DeER vxorps %ymm1, %ymm0, %ymm0

# CHECK: Average Wait times (based on the timeline view):
# CHECK-NEXT: [0]: Executions
Expand All @@ -93,6 +93,6 @@ vxorps %ymm1, %ymm0, %ymm0
# 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 %ymm0, %ymm0, %ymm0
# CHECK-NEXT: 1. 2 3.0 0.0 0.0 vxorps %ymm1, %ymm0, %ymm0
# CHECK-NEXT: 2 2.5 0.3 0.0 <total>
# CHECK-NEXT: 0. 2 0.0 0.0 1.0 vxorps %ymm0, %ymm0, %ymm0
# CHECK-NEXT: 1. 2 1.0 1.0 0.0 vxorps %ymm1, %ymm0, %ymm0
# CHECK-NEXT: 2 0.5 0.5 0.5 <total>

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