clang generate i128 for opencl source but same C/CPP source generate i64 type

[haonanya1]

With the following source, opencl generate i128 but cpp generate i64

void ref_matmul() {
  const __auto_type bin_arg_glob_off = -9223372036854775808L ;
}

opencl IR generated by the command clang++ -cc1 -x cl 2.cl -cl-std=CL2.0 -triple spir64-unknown-unknown -emit-llvm -O0

; Function Attrs: convergent noinline norecurse nounwind optnone
define dso_local spir_func void @ref_matmul() #0 {
entry:
  %bin_arg_glob_off = alloca i128, align 16
  store i128 -9223372036854775808, ptr %bin_arg_glob_off, align 16
  ret void
}

cpp IR generated by the command clang++ 1.cpp -o 1.ll -S -emit-llvm -O0

; Function Attrs: mustprogress noinline nounwind optnone uwtable
define dso_local void @_Z10ref_matmulv() #0 {
  %1 = alloca i64, align 8
  store i64 -9223372036854775808, ptr %1, align 8
  ret void
}

c IR generated by the command clang 1.c -o 1.ll -S -emit-llvm -O0

; Function Attrs: noinline nounwind optnone uwtable
define dso_local void @ref_matmul() #0 {
  %1 = alloca i64, align 8
  store i64 -9223372036854775808, ptr %1, align 8
  ret void
}

is it expected?

@svenvh , thanks very much.

[llvmbot]

@llvm/issue-subscribers-opencl

Author: haonan (haonanya1)

With the following source, opencl generate i128 but cpp generate i64

void ref_matmul() {

  long n = 1;
  const __auto_type bin_arg_glob_off =
      -9223372036854775808L + n % -9223372036854775808L;
}

opencl IR generated by the command clang++ -cc1 -x cl 2.cl -cl-std=CL2.0 -triple spir64-unknown-unknown -emit-llvm -O0

; Function Attrs: convergent noinline norecurse nounwind optnone
define dso_local spir_func void @<!-- -->ref_matmul() #<!-- -->0 {
entry:
  %n = alloca i64, align 8
  %bin_arg_glob_off = alloca i128, align 16
  store i64 1, ptr %n, align 8
  %0 = load i64, ptr %n, align 8
  %conv = sext i64 %0 to i128
  %rem = srem i128 %conv, -9223372036854775808
  %add = add nsw i128 -9223372036854775808, %rem
  store i128 %add, ptr %bin_arg_glob_off, align 16
  ret void
}

cpp IR generated by the command clang++ 1.cpp -o 1.ll -S -emit-llvm -O0

; Function Attrs: mustprogress noinline nounwind optnone uwtable
define dso_local void @<!-- -->_Z10ref_matmulv() #<!-- -->0 {
entry:
  %n = alloca i64, align 8
  %bin_arg_glob_off = alloca i64, align 8
  store i64 1, ptr %n, align 8
  %0 = load i64, ptr %n, align 8
  %rem = urem i64 %0, -9223372036854775808
  %add = add i64 -9223372036854775808, %rem
  store i64 %add, ptr %bin_arg_glob_off, align 8
  ret void
}

is it expected?

@svenvh , thanks very much.

[svenvh]

This will require a bit of investigation to answer. Some next steps to consider:

• The input source does not compile cleanly: 9223372036854775808L is too large to be represented in a signed integer type.
• OpenCL C is based on C99, not on C++. Do you still get the difference when compiling the input as a C program?
• Try comparing the AST dumps, to narrow down where this difference occurs.

[haonanya1]

Thanks @svenvh for your quick reply, I checked ast according to your suggestions.
For cpp bin_arg_glob_off is const unsigned long long which is at least 64 bits according to https://en.cppreference.com/w/cpp/language/types

`-FunctionDecl 0x9797eb0 <2.c:1:1, line:6:1> line:1:6 ref_matmul 'void ()'
  `-CompoundStmt 0x97981b8 <col:19, line:6:1>
    `-DeclStmt 0x97981a0 <line:5:3, col:61>
      `-VarDecl 0x9797fe8 <col:3, col:41> col:21 bin_arg_glob_off 'const unsigned long long' cinit
        `-UnaryOperator 0x9798070 <col:40, col:41> 'unsigned long long' prefix '-'
          `-IntegerLiteral 0x9798050 <col:41> 'unsigned long long' 9223372036854775808

For opencl bin_arg_glob_off is const __private long long which is 128-bit signed integer scalar according to https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_C.html#reserved-data-types.

`-FunctionDecl 0x8c112f0 <2.cl:1:1, line:6:1> line:1:6 ref_matmul 'void (void)'
  `-CompoundStmt 0x8c11628 <col:19, line:6:1>
    `-DeclStmt 0x8c11610 <line:5:3, col:61>
      `-VarDecl 0x8c113e8 <col:3, col:41> col:21 bin_arg_glob_off 'const __private long long' cinit
        `-UnaryOperator 0x8c114a0 <col:40, col:41> 'long long' prefix '-'
          `-IntegerLiteral 0x8c11470 <col:41> 'long long' 9223372036854775808

So it is not an issue, what's your opinion? Thanks.