[PATCH] D123180: [RISCV] Fixing stack offset for RVV object with vararg in stack.

[Kito Cheng via Phabricator via llvm-commits]

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We found LLVM generate wrong stack offset for RVV object when stack
having variable argument, that cause by we didn't count vaarg part during
calculate RVV stack objects.

Also update the stack layout diagram for including vaarg in the diagram.

Ref:
https://github.com/gcc-mirror/gcc/blob/master/gcc/config/riscv/riscv.cc#L3941


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123180

Files:
  llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
  llvm/test/CodeGen/RISCV/wrong-stack-offset-for-rvv-object.mir


Index: llvm/test/CodeGen/RISCV/wrong-stack-offset-for-rvv-object.mir
===================================================================
--- llvm/test/CodeGen/RISCV/wrong-stack-offset-for-rvv-object.mir
+++ llvm/test/CodeGen/RISCV/wrong-stack-offset-for-rvv-object.mir
@@ -164,7 +164,7 @@
   ; CHECK-NEXT:   SD killed renamable $x16, killed $x10, 48 :: (store (s64) into %fixed-stack.1, align 16)
   ; CHECK-NEXT:   dead $x0 = PseudoVSETIVLI 2, 69, implicit-def $vl, implicit-def $vtype
   ; CHECK-NEXT:   renamable $v8 = PseudoVMV_V_I_MF8 0, 2, 3, implicit $vl, implicit $vtype
-  ; CHECK-NEXT:   $x10 = ADDI $x2, 40
+  ; CHECK-NEXT:   $x10 = ADDI $x2, 24
   ; CHECK-NEXT:   PseudoVSPILL_M1 killed renamable $v8, killed $x10 :: (store unknown-size into %stack.1, align 8)
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT: bb.1.while.cond:
@@ -179,7 +179,7 @@
   ; CHECK-NEXT:   liveins: $x8, $x9
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT:   dead $x0 = PseudoVSETIVLI 2, 69, implicit-def $vl, implicit-def $vtype
-  ; CHECK-NEXT:   $x10 = ADDI $x2, 40
+  ; CHECK-NEXT:   $x10 = ADDI $x2, 24
   ; CHECK-NEXT:   renamable $v8 = PseudoVRELOAD_M1 killed $x10 :: (load unknown-size from %stack.1, align 8)
   ; CHECK-NEXT:   PseudoVSE8_V_MF8 killed renamable $v8, renamable $x8, 2, 3, implicit $vl, implicit $vtype :: (store (s16) into %ir.0, align 1)
   ; CHECK-NEXT:   $x10 = COPY renamable $x9
Index: llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -674,7 +674,10 @@
     if (hasBP(MF)) {
       FrameReg = RISCVABI::getBPReg();
       // |--------------------------| -- <-- FP
-      // | callee-saved registers   | | <----.
+      // | callee-allocated save    | | <----|
+      // | area for register varargs| |      |
+      // |--------------------------| |      |
+      // | callee-saved registers   | |      |
       // |--------------------------| --     |
       // | realignment (the size of | |      |
       // | this area is not counted | |      |
@@ -699,7 +702,10 @@
     } else {
       FrameReg = RISCV::X2;
       // |--------------------------| -- <-- FP
-      // | callee-saved registers   | | <----.
+      // | callee-allocated save    | | <----|
+      // | area for register varargs| |      |
+      // |--------------------------| |      |
+      // | callee-saved registers   | |      |
       // |--------------------------| --     |
       // | realignment (the size of | |      |
       // | this area is not counted | |      |
@@ -742,6 +748,9 @@
       // the frame size.
       //
       // |--------------------------| -- <-- FP
+      // | callee-allocated save    | |
+      // | area for register varargs| |
+      // |--------------------------| |
       // | callee-saved registers   | |
       // |--------------------------| | MFI.getStackSize()
       // | scalar local variables   | |
@@ -756,7 +765,10 @@
       // When using SP to access frame objects, we need to add RVV stack size.
       //
       // |--------------------------| -- <-- FP
-      // | callee-saved registers   | | <----.
+      // | callee-allocated save    | | <----|
+      // | area for register varargs| |      |
+      // |--------------------------| |      |
+      // | callee-saved registers   | |      |
       // |--------------------------| --     |
       // | Padding after RVV        | |      |
       // | (not counted in          | |      |
@@ -786,8 +798,11 @@
           Offset += StackOffset::getFixed(MFI.getStackSize());
         }
       } else if (MFI.getStackID(FI) == TargetStackID::ScalableVector) {
+        int ScalarLocalVarSize = MFI.getStackSize() -
+                                 RVFI->getCalleeSavedStackSize() -
+                                 RVFI->getVarArgsSaveSize();
         Offset += StackOffset::get(
-            alignTo(MFI.getStackSize() - RVFI->getCalleeSavedStackSize(), 8),
+            alignTo(ScalarLocalVarSize, 8),
             RVFI->getRVVStackSize());
       }
     }


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