[PATCH] D85009: [Sema][BFloat] Forbid arithmetic on vectors of bfloat.

[Simon Tatham via Phabricator via cfe-commits]

simon_tatham created this revision.
simon_tatham added reviewers: SjoerdMeijer, rjmccall, rsmith, liutianle, RKSimon, craig.topper, jfb, LukeGeeson, fpetrogalli.
Herald added subscribers: cfe-commits, dexonsmith, kristof.beyls.
Herald added a project: clang.
simon_tatham requested review of this revision.

Vectors of bfloat are a storage format only; you're supposed to
explicitly convert them to a wider type to do arithmetic on them.
But currently, if you write something like

  bfloat16x4_t test(bfloat16x4_t a, bfloat16x4_t b) { return a + b; }

then the clang frontend accepts it without error, and (ARM or AArch64)
isel fails to generate code for it.

Added a rule in Sema that forbids the attempt from even being made,
and tests that check it. In particular, we also outlaw arithmetic
between vectors of bfloat and any other vector type.

Patch by Luke Cheeseman.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D85009

Files:
  clang/lib/Sema/SemaExpr.cpp
  clang/test/Sema/arm-bfloat.cpp


Index: clang/test/Sema/arm-bfloat.cpp
===================================================================
--- clang/test/Sema/arm-bfloat.cpp
+++ clang/test/Sema/arm-bfloat.cpp
@@ -27,3 +27,21 @@
   fp16 = bf16; // expected-error {{assigning to '__fp16' from incompatible type '__bf16'}}
   bf16 + (b ? fp16 : bf16); // expected-error {{incompatible operand types ('__fp16' and '__bf16')}}
 }
+
+#include <arm_neon.h>
+
+void test_vector(bfloat16x4_t a, bfloat16x4_t b, float16x4_t c) {
+  a + b; // expected-error {{invalid operands to binary expression ('bfloat16x4_t' (vector of 4 'bfloat16_t' values) and 'bfloat16x4_t')}}
+  a - b; // expected-error {{invalid operands to binary expression ('bfloat16x4_t' (vector of 4 'bfloat16_t' values) and 'bfloat16x4_t')}}
+  a * b; // expected-error {{invalid operands to binary expression ('bfloat16x4_t' (vector of 4 'bfloat16_t' values) and 'bfloat16x4_t')}}
+  a / b; // expected-error {{invalid operands to binary expression ('bfloat16x4_t' (vector of 4 'bfloat16_t' values) and 'bfloat16x4_t')}}
+
+  a + c; // expected-error {{invalid operands to binary expression ('bfloat16x4_t' (vector of 4 'bfloat16_t' values) and 'float16x4_t' (vector of 4 'float16_t' values))}}
+  a - c; // expected-error {{invalid operands to binary expression ('bfloat16x4_t' (vector of 4 'bfloat16_t' values) and 'float16x4_t' (vector of 4 'float16_t' values))}}
+  a * c; // expected-error {{invalid operands to binary expression ('bfloat16x4_t' (vector of 4 'bfloat16_t' values) and 'float16x4_t' (vector of 4 'float16_t' values))}}
+  a / c; // expected-error {{invalid operands to binary expression ('bfloat16x4_t' (vector of 4 'bfloat16_t' values) and 'float16x4_t' (vector of 4 'float16_t' values))}}
+  c + b; // expected-error {{invalid operands to binary expression ('float16x4_t' (vector of 4 'float16_t' values) and 'bfloat16x4_t' (vector of 4 'bfloat16_t' values))}}
+  c - b; // expected-error {{invalid operands to binary expression ('float16x4_t' (vector of 4 'float16_t' values) and 'bfloat16x4_t' (vector of 4 'bfloat16_t' values))}}
+  c * b; // expected-error {{invalid operands to binary expression ('float16x4_t' (vector of 4 'float16_t' values) and 'bfloat16x4_t' (vector of 4 'bfloat16_t' values))}}
+  c / b; // expected-error {{invalid operands to binary expression ('float16x4_t' (vector of 4 'float16_t' values) and 'bfloat16x4_t' (vector of 4 'bfloat16_t' values))}}
+}
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -9790,6 +9790,10 @@
   const VectorType *RHSVecType = RHSType->getAs<VectorType>();
   assert(LHSVecType || RHSVecType);
 
+  if ((LHSVecType && LHSVecType->getElementType()->isBFloat16Type()) ||
+      (RHSVecType && RHSVecType->getElementType()->isBFloat16Type()))
+    return InvalidOperands(Loc, LHS, RHS);
+
   // AltiVec-style "vector bool op vector bool" combinations are allowed
   // for some operators but not others.
   if (!AllowBothBool &&


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