[llvm] [RISCV] Update some of the RVV memory ops in SiFive P400 & P600 sched models (PR #129575)

[Min-Yih Hsu via llvm-commits]

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@@ -368,65 +370,44 @@ def : WriteRes<WriteVSETIVLI, [SiFiveP400SYS]>;
 def : WriteRes<WriteVSETVL, [SiFiveP400SYS]>;
 
 // 7. Vector Loads and Stores
-// FIXME: This unit is still being improved, currently
-// it is based on stage numbers. Estimates are optimistic,
-// latency may be longer.
-foreach mx = SchedMxList in {
-  defvar LMulLat = SiFiveP400GetLMulCycles<mx>.c;
-  defvar IsWorstCase = SiFiveP400IsWorstCaseMX<mx, SchedMxList>.c;
-  let Latency = 8, ReleaseAtCycles = [LMulLat] in {
-    defm "" : LMULWriteResMX<"WriteVLDE",    [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDM",    [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDFF",   [SiFiveP400VLD], mx, IsWorstCase>;
-  }
-  let Latency = 12, ReleaseAtCycles = [LMulLat] in {
-    defm "" : LMULWriteResMX<"WriteVLDS8",   [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDS16",  [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDS32",  [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDS64",  [SiFiveP400VLD], mx, IsWorstCase>;
-  }
-  let Latency = 12, ReleaseAtCycles = [LMulLat] in {
-    defm "" : LMULWriteResMX<"WriteVLDUX8",  [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDUX16", [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDUX32", [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDUX64", [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDOX8",  [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDOX16", [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDOX32", [SiFiveP400VLD], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVLDOX64", [SiFiveP400VLD], mx, IsWorstCase>;
-  }
-}
 
+// Note that the latency of vector loads are measured by consuming the loaded
+// value with vmv.x.s before subtracting the latency of vmv.x.s from the number.
 foreach mx = SchedMxList in {
   defvar LMulLat = SiFiveP400GetLMulCycles<mx>.c;
   defvar IsWorstCase = SiFiveP400IsWorstCaseMX<mx, SchedMxList>.c;
-  let Latency = 8, ReleaseAtCycles = [LMulLat] in {
-    defm "" : LMULWriteResMX<"WriteVSTE",    [SiFiveP400VST], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVSTM",    [SiFiveP400VST], mx, IsWorstCase>;
-  }
-  let Latency = 12, ReleaseAtCycles = [LMulLat] in {
-    defm "" : LMULWriteResMX<"WriteVSTS8",   [SiFiveP400VST], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVSTS16",  [SiFiveP400VST], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVSTS32",  [SiFiveP400VST], mx, IsWorstCase>;
-    defm "" : LMULWriteResMX<"WriteVSTS64",  [SiFiveP400VST], mx, IsWorstCase>;
+  let Latency = 8 in {
+    let ReleaseAtCycles = [LMulLat] in {
+      defm "" : LMULWriteResMX<"WriteVLDE",  [SiFiveP400VLD], mx, IsWorstCase>;
+      defm "" : LMULWriteResMX<"WriteVLDFF", [SiFiveP400VLD], mx, IsWorstCase>;
+
+      defm "" : LMULWriteResMX<"WriteVSTE",  [SiFiveP400VST], mx, IsWorstCase>;
+    }
+
+    // Mask load and store always have EMUL=1.
----------------
mshockwave wrote:

> From the true meaning of EMUL, its technically EMUL=[1/64, 1]. Only a whole register or a fraction as small as 1/64 of a register is used. It's calculated as EMUL=(1/SEW)*LMUL where SEW and LMUL come from VTYPE.

I copied the EMUL=1 description from the spec. Though I understand what you meant about EMUL can go as small as 1/64. I've updated the comment to be EMUL can be "Mask load and store have a maximum EMUL of 1".

https://github.com/llvm/llvm-project/pull/129575