[PATCH] D145938: [RISCV] Pass vector argument by stack correctly.

[Kito Cheng via Phabricator via llvm-commits]

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We've a argument lowering logic to prevent floating-point value pass
passed with bit-conversion, but that rule should not applied to vector
arguments.

---

How to pass argument to `foo`:

  tail call void @foo(i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0,
                      <vscale x 16 x float> zeroinitializer,
                      <vscale x 16 x float> zeroinitializer,
                      <vscale x 16 x float> zeroinitializer)

`foo` take 13 arguments, first 8 argument pass in GPR, and next 2 LMUL 8 vector
arguments passed in v8-v23, and now we run out of argument register for GPR and
vector register, so we must pass last LMUL 8 vector argument by stack.

Which means we should reserve `vlenb * 8` byte for stack for the last
vector argument.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145938

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/test/CodeGen/RISCV/calling-conv-vector-on-stack.ll


Index: llvm/test/CodeGen/RISCV/calling-conv-vector-on-stack.ll
===================================================================
--- llvm/test/CodeGen/RISCV/calling-conv-vector-on-stack.ll
+++ llvm/test/CodeGen/RISCV/calling-conv-vector-on-stack.ll
@@ -1,16 +1,27 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
-; RUN: llc -mtriple=riscv64 -mattr=+v -verify-machineinstrs -treat-scalable-fixed-error-as-warning < %s 2>&1 | FileCheck %s
+; RUN: llc -mtriple=riscv64 -mattr=+v -verify-machineinstrs < %s 2>&1 | FileCheck %s
 
-; CHECK: warning: Invalid size request on a scalable vector
+; CHECK-NOT: warning: Invalid size request on a scalable vector
 
 define void @bar() nounwind {
 ; CHECK-LABEL: bar:
 ; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    addi sp, sp, -96
+; CHECK-NEXT:    sd ra, 88(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s0, 80(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s1, 72(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    addi s0, sp, 96
+; CHECK-NEXT:    csrr a0, vlenb
+; CHECK-NEXT:    slli a0, a0, 3
+; CHECK-NEXT:    sub sp, sp, a0
+; CHECK-NEXT:    andi sp, sp, -64
+; CHECK-NEXT:    mv s1, sp
 ; CHECK-NEXT:    addi sp, sp, -16
-; CHECK-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
 ; CHECK-NEXT:    vsetvli a0, zero, e32, m8, ta, ma
 ; CHECK-NEXT:    vmv.v.i v8, 0
-; CHECK-NEXT:    vs8r.v v8, (sp)
+; CHECK-NEXT:    addi a0, s1, 64
+; CHECK-NEXT:    vs8r.v v8, (a0)
+; CHECK-NEXT:    sd a0, 0(sp)
 ; CHECK-NEXT:    li a0, 0
 ; CHECK-NEXT:    li a1, 0
 ; CHECK-NEXT:    li a2, 0
@@ -21,8 +32,12 @@
 ; CHECK-NEXT:    li a7, 0
 ; CHECK-NEXT:    vmv.v.i v16, 0
 ; CHECK-NEXT:    call foo at plt
-; CHECK-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; CHECK-NEXT:    addi sp, sp, 16
+; CHECK-NEXT:    addi sp, s0, -96
+; CHECK-NEXT:    ld ra, 88(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    ld s0, 80(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    ld s1, 72(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    addi sp, sp, 96
 ; CHECK-NEXT:    ret
 entry:
   tail call void @foo(i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, <vscale x 16 x float> zeroinitializer, <vscale x 16 x float> zeroinitializer, <vscale x 16 x float> zeroinitializer)
Index: llvm/lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -12795,7 +12795,7 @@
 
   // When a floating-point value is passed on the stack, no bit-conversion is
   // needed.
-  if (ValVT.isFloatingPoint()) {
+  if (ValVT.isFloatingPoint() && !ValVT.isScalableVector()) {
     LocVT = ValVT;
     LocInfo = CCValAssign::Full;
   }


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