[llvm] [RISCV] Add call preserved regmask to tail calls. (PR #122181)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/122181

Every call should have regmask operand to indicate what registers are preserved or clobbered by the call. VirtRegRewriter uses this to tell MachineRegisterInfo what registers are clobbered by a function. If the mask isn't present the registers potentially clobbered by a tail called function aren't counted. I have checked ARM, AArch64, and X86 and they all have a regmask operand on their tail calls.

I believe this fixes an issue I'm seeing with IPRA.

>From 60ee4975b3d00644e023030abe3f5094e3bc3ca4 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Wed, 8 Jan 2025 14:22:21 -0800
Subject: [PATCH] [RISCV] Add call preserved regmask to tail calls.

Every call should have regmask operand to indicate what is preserved.
VirtRegRewriter uses this to tell MachineRegisterInfo what registers
are used by a function. If the mask isn't present the registers
potentially clobbered by a tail called function aren't counted. I
have checked ARM, AArch64, and X86 and they all have a regmask
operand on their tail calls.

I believe thie fixes an issue I'm seeing with IPRA.
---
 llvm/lib/Target/RISCV/RISCVISelLowering.cpp | 12 +++++-------
 llvm/test/CodeGen/RISCV/kcfi-isel-mir.ll    |  2 +-
 llvm/test/CodeGen/RISCV/kcfi-mir.ll         |  2 +-
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 2eeca45ac414bd..6c58989b1afb4c 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -20273,13 +20273,11 @@ SDValue RISCVTargetLowering::LowerCall(CallLoweringInfo &CLI,
   for (auto &Reg : RegsToPass)
     Ops.push_back(DAG.getRegister(Reg.first, Reg.second.getValueType()));
 
-  if (!IsTailCall) {
-    // Add a register mask operand representing the call-preserved registers.
-    const TargetRegisterInfo *TRI = Subtarget.getRegisterInfo();
-    const uint32_t *Mask = TRI->getCallPreservedMask(MF, CallConv);
-    assert(Mask && "Missing call preserved mask for calling convention");
-    Ops.push_back(DAG.getRegisterMask(Mask));
-  }
+  // Add a register mask operand representing the call-preserved registers.
+  const TargetRegisterInfo *TRI = Subtarget.getRegisterInfo();
+  const uint32_t *Mask = TRI->getCallPreservedMask(MF, CallConv);
+  assert(Mask && "Missing call preserved mask for calling convention");
+  Ops.push_back(DAG.getRegisterMask(Mask));
 
   // Glue the call to the argument copies, if any.
   if (Glue.getNode())
diff --git a/llvm/test/CodeGen/RISCV/kcfi-isel-mir.ll b/llvm/test/CodeGen/RISCV/kcfi-isel-mir.ll
index 4c47b5f741fa67..2c428cf4ac87c6 100644
--- a/llvm/test/CodeGen/RISCV/kcfi-isel-mir.ll
+++ b/llvm/test/CodeGen/RISCV/kcfi-isel-mir.ll
@@ -20,7 +20,7 @@ define void @f2(ptr noundef %x) #0 {
   ; CHECK-NEXT:   liveins: $x10
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT:   [[COPY:%[0-9]+]]:gprtc = COPY $x10
-  ; CHECK-NEXT:   PseudoTAILIndirect [[COPY]], implicit $x2, cfi-type 12345678
+  ; CHECK-NEXT:   PseudoTAILIndirect [[COPY]], csr_ilp32_lp64, implicit $x2, cfi-type 12345678
   tail call void %x() [ "kcfi"(i32 12345678) ]
   ret void
 }
diff --git a/llvm/test/CodeGen/RISCV/kcfi-mir.ll b/llvm/test/CodeGen/RISCV/kcfi-mir.ll
index f9f383a35358c2..0c0d39a8bf87d3 100644
--- a/llvm/test/CodeGen/RISCV/kcfi-mir.ll
+++ b/llvm/test/CodeGen/RISCV/kcfi-mir.ll
@@ -30,7 +30,7 @@ define void @f2(ptr noundef %x) #0 {
   ; CHECK-NEXT: {{  $}}
   ; CHECK-NEXT:   BUNDLE implicit-def $x6, implicit-def $x6_w, implicit-def $x6_h, implicit-def $x7, implicit-def $x7_w, implicit-def $x7_h, implicit-def $x28, implicit-def $x28_w, implicit-def $x28_h, implicit-def $x29, implicit-def $x29_w, implicit-def $x29_h, implicit-def $x30, implicit-def $x30_w, implicit-def $x30_h, implicit-def $x31, implicit-def $x31_w, implicit-def $x31_h, implicit killed $x10, implicit $x2 {
   ; CHECK-NEXT:     KCFI_CHECK $x10, 12345678, implicit-def $x6, implicit-def $x7, implicit-def $x28, implicit-def $x29, implicit-def $x30, implicit-def $x31
-  ; CHECK-NEXT:     PseudoTAILIndirect killed $x10, implicit $x2
+  ; CHECK-NEXT:     PseudoTAILIndirect killed $x10, csr_ilp32_lp64, implicit $x2
   ; CHECK-NEXT:   }
   tail call void %x() [ "kcfi"(i32 12345678) ]
   ret void