Reverse translation of access + load/store operations for cooperative matrix (#2165)

Implement translation via SPIR-V friendly calls, as:

the LLVM instructions are not capable to accept target extension types;
cooperative matrix is an opaque object and accessing elements is implementation defined, hence we can't use GEP to which AccessChain naturally maps, since GEP has a different meaning.
As for now some BE would need to recognize and define what to do with a call to __spirv_AccessChain(matrix, index). Better option is to map such SPIR-V to an intrinsic or define an appropriate type in LLVM (hence defining rules for GEP and other instructions) , but it's off the table now.

Author: vmaksimo

lib/SPIRV/SPIRVReader.cpp

@@ -2182,6 +2182,10 @@ Value *SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
     auto *AC = static_cast<SPIRVAccessChainBase *>(BV);
     auto *Base = transValue(AC->getBase(), F, BB);
     SPIRVType *BaseSPVTy = AC->getBase()->getType();
+    if (BaseSPVTy->isTypePointer() &&
+        BaseSPVTy->getPointerElementType()->isTypeCooperativeMatrixKHR()) {
+      return mapValue(BV, transSPIRVBuiltinFromInst(AC, BB));
+    }
     Type *BaseTy =
         BaseSPVTy->isTypeVector()
             ? transType(

test/extensions/KHR/SPV_KHR_cooperative_matrix/access_store.ll

@@ -3,9 +3,8 @@
 ; RUN: llvm-spirv %t.spv -to-text -o %t.spt
 ; RUN: FileCheck < %t.spt %s --check-prefix=CHECK-SPIRV
 
-; TODO: come up with an approach and implement reverse translation
-; R/UN: llvm-spirv -r %t.spv -o %t.rev.bc
-; R/UN: llvm-dis < %t.rev.bc | FileCheck %s --check-prefix=CHECK-LLVM
+; RUN: llvm-spirv -r %t.spv -o %t.rev.bc
+; RUN: llvm-dis < %t.rev.bc | FileCheck %s --check-prefix=CHECK-LLVM
 
 ; CHECK-SPIRV: TypeInt [[#TypeInt:]] 32 0
 ; CHECK-SPIRV-DAG: Constant [[#TypeInt]] [[#Const0:]] 0
@@ -15,28 +14,38 @@
 ; CHECK-SPIRV-DAG: Constant [[#TypeInt]] [[#Const42:]] 42
 
 ; CHECK-SPIRV: TypeCooperativeMatrixKHR [[#TypeMatrix:]] [[#TypeInt]] [[#Const3]] [[#Const12]] [[#Const12]] [[#Const0]]
-; CHECK-SPIRV: TypePointer [[#Type:]] 7 [[#TypeInt]]
+; CHECK-SPIRV: TypePointer [[#TypeMatrixPtr:]] 7 [[#TypeMatrix]]
+; CHECK-SPIRV: TypePointer [[#TypeIntPtr:]] 7 [[#TypeInt]]
 
+; CHECK-SPIRV: Variable [[#TypeMatrixPtr]] [[#VarMatrixPtr:]] 7
 ; CHECK-SPIRV: CompositeConstruct [[#TypeMatrix]] [[#Composite:]] [[#Const0]]
-; CHECK-SPIRV: AccessChain [[#Type]] [[#Res:]] [[#Composite]] [[#Const1]]
+; CHECK-SPIRV: Store [[#VarMatrixPtr]] [[#Composite]]
+; CHECK-SPIRV: AccessChain [[#TypeIntPtr]] [[#Res:]] [[#VarMatrixPtr]] [[#Const1]]
 ; CHECK-SPIRV: Store [[#Res]] [[#Const42]]
 
+; CHECK-LLVM: %0 = alloca target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0)
+; CHECK-LLVM: %Obj = call spir_func target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0) @_Z26__spirv_CompositeConstructi(i32 0)
+; CHECK-LLVM: store target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0) %Obj, ptr %0
+; CHECK-LLVM: %call = call spir_func ptr @_Z19__spirv_AccessChainPPU3AS144__spirv_CooperativeMatrixKHR__uint_3_12_12_0i(ptr %0, i32 1)
+; CHECK-LLVM: store i32 42, ptr %call
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "spir64-unknown-unknown"
 
 ; Function Attrs: mustprogress uwtable
 define dso_local void @_Z3fooi(i32 noundef %idx) local_unnamed_addr #0 {
 entry:
+  %0 = alloca target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0), align 8
   %Obj = tail call spir_func noundef target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0) @_Z26__spirv_CompositeConstruct(i32 noundef 0) #4
-  %call = call noundef ptr @_Z19__spirv_AccessChainP6Matrixii(target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0) %Obj, i32 noundef 1)
+  store target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0) %Obj, ptr %0, align 8
+  %call = call noundef ptr @_Z19__spirv_AccessChainP6Matrixii(ptr %0, i32 noundef 1)
   call void @_Z13__spirv_StorePii(ptr noundef %call, i32 noundef 42)
   ret void
 }
 
 declare dso_local spir_func noundef target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0) @_Z26__spirv_CompositeConstruct(i32 noundef) local_unnamed_addr #2
 
-declare noundef ptr @_Z19__spirv_AccessChainP6Matrixii(target("spirv.CooperativeMatrixKHR", i32, 3, 12, 12, 0) noundef, i32 noundef) local_unnamed_addr #2
+declare noundef ptr @_Z19__spirv_AccessChainP6Matrixii(ptr noundef, i32 noundef) local_unnamed_addr #2
 
 declare void @_Z13__spirv_StorePii(ptr noundef, i32 noundef) local_unnamed_addr #2