Index: llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -690,39 +690,49 @@
     return Offset;
   }
 
+
+  // From here, we first select a legal base register to index off, and then
+  // compute the offset expression.  The index expression can't cross a unknown
+  // variable sized region.  We have at two most such regions: 1) dynamic stack
+  // realignment, and 2) variable sized objects.  Both are optional, and may or
+  // may not exist.  Scalable vectors are variable, but not unknown.  We can
+  // compute offset expressions which cross the RVV region.
+  //
+  // Here's what the stack layout looks like:
+  // |--------------------------| -- <-- FP (if present)
+  // | callee-allocated save    | | <----|
+  // | area for register varargs| |      |
+  // |--------------------------| |      |
+  // | callee-saved registers   | |      |
+  // |--------------------------| --     |
+  // | realignment (the size of | |      |
+  // | this area is not counted | |      |
+  // | in MFI.getStackSize())   | |      |
+  // |--------------------------| --     |-- MFI.getStackSize()
+  // | RVV alignment padding    | |      |
+  // | (not counted in          | |      |
+  // | MFI.getStackSize() but   | |      |
+  // | counted in               | |      |
+  // | RVFI.getRVVStackSize())  | |      |
+  // |--------------------------| --     |
+  // | RVV objects              | |      |
+  // | (not counted in          | |      |
+  // | MFI.getStackSize())      | |      |
+  // |--------------------------| --     |
+  // | padding before RVV       | |      |
+  // | (not counted in          | |      |
+  // | MFI.getStackSize() or in | |      |
+  // | RVFI.getRVVStackSize())  | |      |
+  // |--------------------------| --     |
+  // | scalar local variables   | | <----'
+  // |--------------------------| -- <-- BP (if var sized objects present)
+  // | VarSize objects          | |
+  // |--------------------------| -- <-- SP
+
   if (RI->hasStackRealignment(MF) && !MFI.isFixedObjectIndex(FI)) {
     // If the stack was realigned, the frame pointer is set in order to allow
     // SP to be restored, so we need another base register to record the stack
     // after realignment.
-    // |--------------------------| -- <-- FP
-    // | callee-allocated save    | | <----|
-    // | area for register varargs| |      |
-    // |--------------------------| |      |
-    // | callee-saved registers   | |      |
-    // |--------------------------| --     |
-    // | realignment (the size of | |      |
-    // | this area is not counted | |      |
-    // | in MFI.getStackSize())   | |      |
-    // |--------------------------| --     |-- MFI.getStackSize()
-    // | RVV alignment padding    | |      |
-    // | (not counted in          | |      |
-    // | MFI.getStackSize() but   | |      |
-    // | counted in               | |      |
-    // | RVFI.getRVVStackSize())  | |      |
-    // |--------------------------| --     |
-    // | RVV objects              | |      |
-    // | (not counted in          | |      |
-    // | MFI.getStackSize())      | |      |
-    // |--------------------------| --     |
-    // | padding before RVV       | |      |
-    // | (not counted in          | |      |
-    // | MFI.getStackSize() or in | |      |
-    // | RVFI.getRVVStackSize())  | |      |
-    // |--------------------------| --     |
-    // | scalar local variables   | | <----'
-    // |--------------------------| -- <-- BP (if var sized objects present)
-    // | VarSize objects          | |
-    // |--------------------------| -- <-- SP
     if (hasBP(MF)) {
       FrameReg = RISCVABI::getBPReg();
     } else {
@@ -740,19 +750,6 @@
       Offset -= StackOffset::getFixed(RVFI->getLibCallStackSize());
     // When using FP to access scalable vector objects, we need to minus
     // the frame size.
-    //
-    // |--------------------------| -- <-- FP
-    // | callee-allocated save    | |
-    // | area for register varargs| |
-    // |--------------------------| |
-    // | callee-saved registers   | |
-    // |--------------------------| | MFI.getStackSize()
-    // | scalar local variables   | |
-    // |--------------------------| -- (Offset of RVV objects is from here.)
-    // | RVV objects              |
-    // |--------------------------|
-    // | VarSize objects          |
-    // |--------------------------| <-- SP
     if (MFI.getStackID(FI) == TargetStackID::ScalableVector) {
       assert(!RI->hasStackRealignment(MF) &&
              "Can't index across variable sized realign");
@@ -771,32 +768,6 @@
   assert(FrameReg == RISCVABI::getBPReg() || !MFI.hasVarSizedObjects());
 
   // When using SP to access frame objects, we need to add RVV stack size.
-  //
-  // |--------------------------| -- <-- FP
-  // | callee-allocated save    | | <----|
-  // | area for register varargs| |      |
-  // |--------------------------| |      |
-  // | callee-saved registers   | |      |
-  // |--------------------------| --     |
-  // | RVV alignment padding    | |      |
-  // | (not counted in          | |      |
-  // | MFI.getStackSize() but   | |      |
-  // | counted in               | |      |
-  // | RVFI.getRVVStackSize())  | |      |
-  // |--------------------------| --     |
-  // | RVV objects              | |      |-- MFI.getStackSize()
-  // | (not counted in          | |      |
-  // | MFI.getStackSize())      | |      |
-  // |--------------------------| --     |
-  // | padding before RVV       | |      |
-  // | (not counted in          | |      |
-  // | MFI.getStackSize())      | |      |
-  // |--------------------------| --     |
-  // | scalar local variables   | | <----'
-  // |--------------------------| -- <-- BP (if var sized objects present)
-  // | VarSize objects          | |
-  // |--------------------------| -- <-- SP
-  //
   // The total amount of padding surrounding RVV objects is described by
   // RVV->getRVVPadding() and it can be zero. It allows us to align the RVV
   // objects to the required alignment.