[llvm] [SPIRV] selectDot4AddPacked: add missing PackedVectorFormat4x8Bit optional operand (PR #179476)

[Juan Manuel Martinez Caamaño via llvm-commits]

https://github.com/jmmartinez updated https://github.com/llvm/llvm-project/pull/179476

>From 2692000d202e0ea317d568ec8e07c13c60f91b55 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Manuel=20Martinez=20Caama=C3=B1o?=
 <jmartinezcaamao at gmail.com>
Date: Tue, 3 Feb 2026 15:42:08 +0100
Subject: [PATCH] [SPIRV] selectDot4AddPacked: add missing
 PackedVectorFormat4x8Bit optional operand

According to SPIRV:

```
PackedVectorFormat4x8Bit (PackedVectorFormat4x8BitKHR)

Interpret 32-bit scalar integer operands as vectors of four 8-bit
components. Vector components follow byte significance order with the
lowest-numbered component stored in the least significant byte.
```

And in OpSDot / OpUDot:

```
When Vector 1 and Vector 2 are scalar integer types, Packed Vector
Format must be specified to select how the integers are to be
interpreted as vectors.
```
---
 .../Target/SPIRV/SPIRVInstructionSelector.cpp | 26 ++++++++++---------
 .../SPIRV/hlsl-intrinsics/dot4add_i8packed.ll |  2 +-
 .../SPIRV/hlsl-intrinsics/dot4add_u8packed.ll |  2 +-
 3 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
index 765fa6277d4ca..6efd48761dafe 100644
--- a/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
+++ b/llvm/lib/Target/SPIRV/SPIRVInstructionSelector.cpp
@@ -2534,19 +2534,21 @@ bool SPIRVInstructionSelector::selectDot4AddPacked(Register ResVReg,
 
   auto DotOp = Signed ? SPIRV::OpSDot : SPIRV::OpUDot;
   Register Dot = MRI->createVirtualRegister(GR.getRegClass(ResType));
-  bool Result = BuildMI(BB, I, I.getDebugLoc(), TII.get(DotOp))
-                    .addDef(Dot)
-                    .addUse(GR.getSPIRVTypeID(ResType))
-                    .addUse(X)
-                    .addUse(Y)
-                    .constrainAllUses(TII, TRI, RBI);
+  auto MIB = BuildMI(BB, I, I.getDebugLoc(), TII.get(DotOp))
+                 .addDef(Dot)
+                 .addUse(GR.getSPIRVTypeID(ResType))
+                 .addUse(X)
+                 .addUse(Y);
+  MIB.addImm(SPIRV::BuiltIn::PackedVectorFormat4x8Bit);
+  MIB.constrainAllUses(TII, TRI, RBI);
 
-  return Result && BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpIAddS))
-                       .addDef(ResVReg)
-                       .addUse(GR.getSPIRVTypeID(ResType))
-                       .addUse(Dot)
-                       .addUse(Acc)
-                       .constrainAllUses(TII, TRI, RBI);
+  BuildMI(BB, I, I.getDebugLoc(), TII.get(SPIRV::OpIAddS))
+      .addDef(ResVReg)
+      .addUse(GR.getSPIRVTypeID(ResType))
+      .addUse(Dot)
+      .addUse(Acc)
+      .constrainAllUses(TII, TRI, RBI);
+  return true;
 }
 
 // Since pre-1.6 SPIRV has no DotProductInput4x8BitPacked implementation,
diff --git a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/dot4add_i8packed.ll b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/dot4add_i8packed.ll
index 9ff4babd8a918..f756762755b51 100644
--- a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/dot4add_i8packed.ll
+++ b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/dot4add_i8packed.ll
@@ -25,7 +25,7 @@ entry:
 
 ; Test that we use the dot product op when capabilities allow
 
-; CHECK-DOT: %[[#DOT:]] = OpSDot %[[#int_32]] %[[#X]] %[[#Y]]
+; CHECK-DOT: %[[#DOT:]] = OpSDot %[[#int_32]] %[[#X]] %[[#Y]] PackedVectorFormat4x8Bit
 ; CHECK-DOT: %[[#RES:]] = OpIAdd %[[#int_32]] %[[#DOT]] %[[#ACC]]
 
 ; Test expansion is used when spirv dot product capabilities aren't available:
diff --git a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/dot4add_u8packed.ll b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/dot4add_u8packed.ll
index 5e41c9dc79dd2..907cf622f609f 100644
--- a/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/dot4add_u8packed.ll
+++ b/llvm/test/CodeGen/SPIRV/hlsl-intrinsics/dot4add_u8packed.ll
@@ -25,7 +25,7 @@ entry:
 
 ; Test that we use the dot product op when capabilities allow
 
-; CHECK-DOT: %[[#DOT:]] = OpUDot %[[#int_32]] %[[#X]] %[[#Y]]
+; CHECK-DOT: %[[#DOT:]] = OpUDot %[[#int_32]] %[[#X]] %[[#Y]] PackedVectorFormat4x8Bit
 ; CHECK-DOT: %[[#RES:]] = OpIAdd %[[#int_32]] %[[#DOT]] %[[#ACC]]
 
 ; Test expansion is used when spirv dot product capabilities aren't available: