[llvm] [AMDGPU] Fix broken uses of isLegalFLATOffset and splitFlatOffset (PR #147469)

[Fabian Ritter via llvm-commits]

https://github.com/ritter-x2a created https://github.com/llvm/llvm-project/pull/147469

The last parameter of these functions used to be `Signed`, and it looks like a few calls weren't updated when that was changed to `FlatVariant`. Effectively, the functions were called with `FlatVariant=SALU` due to integer promotions, which doesn't make any sense.

>From 1393a3d41247a65f322533da51a29554e5eb6c34 Mon Sep 17 00:00:00 2001
From: Fabian Ritter <fabian.ritter at amd.com>
Date: Tue, 8 Jul 2025 03:16:36 -0400
Subject: [PATCH] [AMDGPU] Fix broken uses of isLegalFLATOffset and
 splitFlatOffset

The last parameter of these functions used to be `Signed`, and it looks
like a few calls weren't updated when that was changed to `FlatVariant`.
Effectively, the functions were called with `FlatVariant=SALU` due to
integer promotions, which doesn't make any sense.
---
 llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp        | 7 ++++---
 llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp | 3 ++-
 llvm/lib/Target/AMDGPU/SIInstrInfo.h                 | 3 +--
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp b/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
index 6e990cb2e160c..202693b316122 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
@@ -2032,7 +2032,8 @@ bool AMDGPUDAGToDAGISel::SelectScratchSVAddr(SDNode *N, SDValue Addr,
     int64_t COffsetVal = cast<ConstantSDNode>(RHS)->getSExtValue();
     const SIInstrInfo *TII = Subtarget->getInstrInfo();
 
-    if (TII->isLegalFLATOffset(COffsetVal, AMDGPUAS::PRIVATE_ADDRESS, true)) {
+    if (TII->isLegalFLATOffset(COffsetVal, AMDGPUAS::PRIVATE_ADDRESS,
+                               SIInstrFlags::FlatScratch)) {
       Addr = LHS;
       ImmOffset = COffsetVal;
     } else if (!LHS->isDivergent() && COffsetVal > 0) {
@@ -2040,8 +2041,8 @@ bool AMDGPUDAGToDAGISel::SelectScratchSVAddr(SDNode *N, SDValue Addr,
       // saddr + large_offset -> saddr + (vaddr = large_offset & ~MaxOffset) +
       //                         (large_offset & MaxOffset);
       int64_t SplitImmOffset, RemainderOffset;
-      std::tie(SplitImmOffset, RemainderOffset)
-        = TII->splitFlatOffset(COffsetVal, AMDGPUAS::PRIVATE_ADDRESS, true);
+      std::tie(SplitImmOffset, RemainderOffset) = TII->splitFlatOffset(
+          COffsetVal, AMDGPUAS::PRIVATE_ADDRESS, SIInstrFlags::FlatScratch);
 
       if (isUInt<32>(RemainderOffset)) {
         SDNode *VMov = CurDAG->getMachineNode(
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp b/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
index b632b16f5c198..9f0cde444f94b 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
@@ -5070,7 +5070,8 @@ AMDGPUInstructionSelector::selectScratchSVAddr(MachineOperand &Root) const {
 
   Register OrigAddr = Addr;
   if (ConstOffset != 0 &&
-      TII.isLegalFLATOffset(ConstOffset, AMDGPUAS::PRIVATE_ADDRESS, true)) {
+      TII.isLegalFLATOffset(ConstOffset, AMDGPUAS::PRIVATE_ADDRESS,
+                            SIInstrFlags::FlatScratch)) {
     Addr = PtrBase;
     ImmOffset = ConstOffset;
   }
diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.h b/llvm/lib/Target/AMDGPU/SIInstrInfo.h
index 01dd3c9f4119e..9e84822bfc273 100644
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.h
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.h
@@ -1448,8 +1448,7 @@ class SIInstrInfo final : public AMDGPUGenInstrInfo {
                         Align Alignment = Align(4)) const;
 
   /// Returns if \p Offset is legal for the subtarget as the offset to a FLAT
-  /// encoded instruction. If \p Signed, this is for an instruction that
-  /// interprets the offset as signed.
+  /// encoded instruction with the given \p FlatVariant.
   bool isLegalFLATOffset(int64_t Offset, unsigned AddrSpace,
                          uint64_t FlatVariant) const;