[PATCH] D126400: [RISCV] Allow compatible VTYPE in AVL Reg Forward cases

[Philip Reames via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGafe49934a68a: [RISCV] Allow compatible VTYPE in AVL Reg Forward cases (authored by reames).

Changed prior to commit:
  https://reviews.llvm.org/D126400?vs=432049&id=432301#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D126400/new/

https://reviews.llvm.org/D126400

Files:
  llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
  llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll


Index: llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
===================================================================
--- llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
+++ llvm/test/CodeGen/RISCV/rvv/vsetvli-insert-crossbb.ll
@@ -816,7 +816,6 @@
 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    vsetivli a0, 6, e32, m2, tu, mu
 ; CHECK-NEXT:    vmv.s.x v8, a0
-; CHECK-NEXT:    vsetvli zero, a0, e32, m2, tu, mu
 ; CHECK-NEXT:    vadd.vv v8, v8, v10, v0.t
 ; CHECK-NEXT:    ret
                                          <vscale x 4 x i1> %mask) {
Index: llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
@@ -202,6 +202,9 @@
   }
 
   // Check if the VTYPE for these two VSETVLIInfos produce the same VLMAX.
+  // Note that having the same VLMAX ensures that both share the same
+  // function from AVL to VL; that is, they must produce the same VL value
+  // for any given AVL value.
   bool hasSameVLMAX(const VSETVLIInfo &Other) const {
     assert(isValid() && Other.isValid() &&
            "Can't compare invalid VSETVLIInfos");
@@ -717,7 +720,7 @@
     return false;
 
   // We didn't find a compatible value. If our AVL is a virtual register,
-  // it might be defined by a VSET(I)VLI. If it has the same VTYPE we need
+  // it might be defined by a VSET(I)VLI. If it has the same VLMAX we need
   // and the last VL/VTYPE we observed is the same, we don't need a
   // VSETVLI here.
   if (!CurInfo.isUnknown() && Require.hasAVLReg() &&
@@ -726,7 +729,7 @@
     if (MachineInstr *DefMI = MRI->getVRegDef(Require.getAVLReg())) {
       if (isVectorConfigInstr(*DefMI)) {
         VSETVLIInfo DefInfo = getInfoForVSETVLI(*DefMI);
-        if (DefInfo.hasSameAVL(CurInfo) && DefInfo.hasSameVTYPE(CurInfo))
+        if (DefInfo.hasSameAVL(CurInfo) && DefInfo.hasSameVLMAX(CurInfo))
           return false;
       }
     }
@@ -1237,7 +1240,7 @@
           }
         }
 
-        // If AVL is defined by a vsetvli with the same vtype, we can
+        // If AVL is defined by a vsetvli with the same VLMAX, we can
         // replace the AVL operand with the AVL of the defining vsetvli.
         // We avoid general register AVLs to avoid extending live ranges
         // without being sure we can kill the original source reg entirely.
@@ -1246,7 +1249,7 @@
           if (MachineInstr *DefMI = MRI->getVRegDef(Require.getAVLReg())) {
             if (isVectorConfigInstr(*DefMI)) {
               VSETVLIInfo DefInfo = getInfoForVSETVLI(*DefMI);
-              if (DefInfo.hasSameVTYPE(Require) &&
+              if (DefInfo.hasSameVLMAX(Require) &&
                   (DefInfo.hasAVLImm() || DefInfo.getAVLReg() == RISCV::X0)) {
                 MachineOperand &VLOp = MI.getOperand(getVLOpNum(MI));
                 if (DefInfo.hasAVLImm())


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