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

As confirmed by exegesis measurements, and ref docs.

diff --git a/llvm/lib/Target/X86/X86ScheduleZnver3.td b/llvm/lib/Target/X86/X86ScheduleZnver3.td
index 6d2a88c..63537a4 100644 (file)
--- a/llvm/lib/Target/X86/X86ScheduleZnver3.td
+++ b/llvm/lib/Target/X86/X86ScheduleZnver3.td
@@ -1535,7 +1535,7 @@ def Zn3WriteFZeroIdiom : SchedWriteVariant<[
     SchedVar<NoSchedPred,                          [WriteFLogic]>
 ]>;
 // NOTE: XORPSrr, XORPDrr are not zero-cycle!
-def : InstRW<[Zn3WriteFZeroIdiom], (instrs VXORPSrr)>;
+def : InstRW<[Zn3WriteFZeroIdiom], (instrs VXORPSrr, VXORPDrr)>;
 
 def Zn3WriteFZeroIdiomY : SchedWriteVariant<[
     SchedVar<MCSchedPredicate<ZeroIdiomPredicate>, [Zn3WriteZeroLatency]>,
@@ -1554,7 +1554,7 @@ def : IsZeroIdiomFunction<[
   DepBreakingClass<[ XORPSrr, XORPDrr ], ZeroIdiomPredicate>,
 
   // AVX XMM Zero-idioms.
-  DepBreakingClass<[ VXORPSrr ], ZeroIdiomPredicate>,
+  DepBreakingClass<[ VXORPSrr, VXORPDrr ], ZeroIdiomPredicate>,
 
   // AVX YMM Zero-idioms.
   DepBreakingClass<[ VXORPSYrr ], ZeroIdiomPredicate>,

diff --git a/llvm/test/tools/llvm-mca/X86/Znver3/zero-idioms-avx-xmm.s b/llvm/test/tools/llvm-mca/X86/Znver3/zero-idioms-avx-xmm.s
index 2c8de4c..6288c87 100644 (file)
--- a/llvm/test/tools/llvm-mca/X86/Znver3/zero-idioms-avx-xmm.s
+++ b/llvm/test/tools/llvm-mca/X86/Znver3/zero-idioms-avx-xmm.s
@@ -106,13 +106,13 @@ vxorpd %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
@@ -123,17 +123,17 @@ vxorpd %xmm1, %xmm0, %xmm0
 # CHECK-NEXT: [6]: HasSideEffects (U)
 
 # CHECK:      [1]    [2]    [3]    [4]    [5]    [6]    Instructions:
-# CHECK-NEXT:  1      1     0.25                        vxorpd %xmm0, %xmm0, %xmm0
+# CHECK-NEXT:  1      0     0.17                        vxorpd %xmm0, %xmm0, %xmm0
 # CHECK-NEXT:  1      1     0.25                        vxorpd %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
@@ -167,20 +167,20 @@ vxorpd %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    -      -      -      -      -      -      -      -      -      -      -     vxorpd  %xmm0, %xmm0, %xmm0
-# CHECK-NEXT:  -      -      -      -      -      -      -      -     0.50    -     0.50    -      -      -      -      -      -      -      -      -      -      -      -     vxorpd  %xmm1, %xmm0, %xmm0
+# CHECK-NEXT:  -      -      -      -      -      -      -      -      -      -      -      -      -      -      -      -      -      -      -      -      -      -      -     vxorpd  %xmm0, %xmm0, %xmm0
+# CHECK-NEXT:  -      -      -      -      -      -      -      -     0.25   0.25   0.25   0.25    -      -      -      -      -      -      -      -      -      -      -     vxorpd  %xmm1, %xmm0, %xmm0
 
 # CHECK:      Timeline view:
-# CHECK-NEXT: Index     0123456
+# CHECK-NEXT: Index     0123
 
-# CHECK:      [0,0]     DeER ..   vxorpd       %xmm0, %xmm0, %xmm0
-# CHECK-NEXT: [0,1]     D=eER..   vxorpd       %xmm1, %xmm0, %xmm0
-# CHECK-NEXT: [1,0]     D==eER.   vxorpd       %xmm0, %xmm0, %xmm0
-# CHECK-NEXT: [1,1]     D===eER   vxorpd       %xmm1, %xmm0, %xmm0
+# CHECK:      [0,0]     DR .   vxorpd  %xmm0, %xmm0, %xmm0
+# CHECK-NEXT: [0,1]     DeER   vxorpd  %xmm1, %xmm0, %xmm0
+# CHECK-NEXT: [1,0]     D--R   vxorpd  %xmm0, %xmm0, %xmm0
+# CHECK-NEXT: [1,1]     DeER   vxorpd  %xmm1, %xmm0, %xmm0
 
 # CHECK:      Average Wait times (based on the timeline view):
 # CHECK-NEXT: [0]: Executions
@@ -189,6 +189,6 @@ vxorpd %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       vxorpd      %xmm0, %xmm0, %xmm0
-# CHECK-NEXT: 1.     2     3.0    0.0    0.0       vxorpd      %xmm1, %xmm0, %xmm0
-# CHECK-NEXT:        2     2.5    0.3    0.0       <total>
+# CHECK-NEXT: 0.     2     0.0    0.0    1.0       vxorpd      %xmm0, %xmm0, %xmm0
+# CHECK-NEXT: 1.     2     1.0    1.0    0.0       vxorpd      %xmm1, %xmm0, %xmm0
+# CHECK-NEXT:        2     0.5    0.5    0.5       <total>