[llvm] [RISCV][GISel] Fallback in LowerCall for byval arguments. (PR #119251)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/119251

Our byval call lowering isn't copying the argument. Looks like the SelectionDAG code for byval is different than AArch64 so this may be non-trivial to fix. Reject for now.

>From 5a5864fdc54948996569c0b43d51414a2649ca82 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Mon, 9 Dec 2024 11:16:19 -0800
Subject: [PATCH] [RISCV][GISel] Fallback in LowerCall for byval arguments.

Our byval call lowering isn't copying the argument. Looks like the
SelectionDAG code for byval is different than AArch64 so this may
be non-trivial to fix. Reject for now.
---
 .../Target/RISCV/GISel/RISCVCallLowering.cpp  |  2 ++
 .../RISCV/GlobalISel/irtranslator/calls.ll    | 25 -------------------
 .../RISCV/GlobalISel/riscv-unsupported.ll     | 16 ++++++++++++
 3 files changed, 18 insertions(+), 25 deletions(-)
 create mode 100644 llvm/test/CodeGen/RISCV/GlobalISel/riscv-unsupported.ll

diff --git a/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp b/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
index 800f886dd70830..e451f535809c20 100644
--- a/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
@@ -596,6 +596,8 @@ bool RISCVCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
   for (auto &AInfo : Info.OrigArgs) {
     if (!isSupportedArgumentType(AInfo.Ty, Subtarget))
       return false;
+    if (AInfo.Flags[0].isByVal())
+      return false;
   }
 
   if (!Info.OrigRet.Ty->isVoidTy() &&
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/irtranslator/calls.ll b/llvm/test/CodeGen/RISCV/GlobalISel/irtranslator/calls.ll
index b06b539ded19b9..34e29718d0e9a6 100644
--- a/llvm/test/CodeGen/RISCV/GlobalISel/irtranslator/calls.ll
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/irtranslator/calls.ll
@@ -350,31 +350,6 @@ entry:
 %struct.Foo = type { i32, i32, i32, i16, i8 }
 @foo = global %struct.Foo { i32 1, i32 2, i32 3, i16 4, i8 5 }, align 4
 
-declare void @void_byval_args(ptr byval(%struct.Foo) %f)
-
-define void @test_void_byval_args() {
-  ; RV32I-LABEL: name: test_void_byval_args
-  ; RV32I: bb.1.entry:
-  ; RV32I-NEXT:   [[GV:%[0-9]+]]:_(p0) = G_GLOBAL_VALUE @foo
-  ; RV32I-NEXT:   ADJCALLSTACKDOWN 0, 0, implicit-def $x2, implicit $x2
-  ; RV32I-NEXT:   $x10 = COPY [[GV]](p0)
-  ; RV32I-NEXT:   PseudoCALL target-flags(riscv-call) @void_byval_args, csr_ilp32_lp64, implicit-def $x1, implicit $x10
-  ; RV32I-NEXT:   ADJCALLSTACKUP 0, 0, implicit-def $x2, implicit $x2
-  ; RV32I-NEXT:   PseudoRET
-  ;
-  ; RV64I-LABEL: name: test_void_byval_args
-  ; RV64I: bb.1.entry:
-  ; RV64I-NEXT:   [[GV:%[0-9]+]]:_(p0) = G_GLOBAL_VALUE @foo
-  ; RV64I-NEXT:   ADJCALLSTACKDOWN 0, 0, implicit-def $x2, implicit $x2
-  ; RV64I-NEXT:   $x10 = COPY [[GV]](p0)
-  ; RV64I-NEXT:   PseudoCALL target-flags(riscv-call) @void_byval_args, csr_ilp32_lp64, implicit-def $x1, implicit $x10
-  ; RV64I-NEXT:   ADJCALLSTACKUP 0, 0, implicit-def $x2, implicit $x2
-  ; RV64I-NEXT:   PseudoRET
-entry:
-  call void @void_byval_args(ptr byval(%struct.Foo) @foo)
-  ret void
-}
-
 declare void @void_sret_args(ptr sret(%struct.Foo) %f)
 
 define void @test_void_sret_args() {
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/riscv-unsupported.ll b/llvm/test/CodeGen/RISCV/GlobalISel/riscv-unsupported.ll
new file mode 100644
index 00000000000000..073b5186aad718
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/riscv-unsupported.ll
@@ -0,0 +1,16 @@
+; RUN: llc -mtriple=riscv32 -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed='gisel*' %s -o - 2>&1 | FileCheck %s -check-prefixes=CHECK
+; RUN: llc -mtriple=riscv64 -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed='gisel*' %s -o - 2>&1 | FileCheck %s -check-prefixes=CHECK
+
+; This file checks that we use the fallback path for things that are known to
+; be unsupported on the RISC-V target. It should progressively shrink in size.
+
+%byval.class = type { i32 }
+
+declare void @test_byval_arg(ptr byval(%byval.class) %x)
+
+define void @test_byval_param(ptr %x) {
+; CHECK: remark: {{.*}} unable to translate instruction: call
+; CHECK-LABEL: warning: Instruction selection used fallback path for test_byval_param
+  call void @test_byval_arg(ptr byval(%byval.class) %x)
+  ret void
+}