[clang] 1b1b30c - [clang][SVE] Don't warn on vector to sizeless builtin implicit conversion

[Joe Ellis via cfe-commits]

Author: Joe Ellis
Date: 2021-02-23T13:40:58Z
New Revision: 1b1b30cf0f7d9619afb32e16f4a7c007da4ffccf

URL: https://github.com/llvm/llvm-project/commit/1b1b30cf0f7d9619afb32e16f4a7c007da4ffccf
DIFF: https://github.com/llvm/llvm-project/commit/1b1b30cf0f7d9619afb32e16f4a7c007da4ffccf.diff

LOG: [clang][SVE] Don't warn on vector to sizeless builtin implicit conversion

This commit prevents warnings from -Wconversion when a clang vector type
is implicitly converted to a sizeless builtin type -- for example, when
implicitly converting a fixed-predicate to a scalable predicate.

The code below:

     1    #include <arm_sve.h>
     2
     3    #define N __ARM_FEATURE_SVE_BITS
     4    #define FIXED_ATTR __attribute__((arm_sve_vector_bits (N)))
     5    typedef svbool_t fixed_svbool_t FIXED_ATTR;
     6
     7    inline fixed_svbool_t foo(fixed_svbool_t p) {
     8      return svnot_z(svptrue_b64(), p);
     9    }

would previously raise this warning:

    warning: implicit conversion turns vector to scalar: \
    'fixed_svbool_t' (vector of 8 'unsigned char' values) to 'svbool_t' \
    (aka '__SVBool_t') [-Wconversion]

Note that many cases of these implicit conversions were already
permitted because many functions inside arm_sve.h are spawned via
preprocessor macros, and the call to isInSystemMacro would cover us in
this case. This commit fixes the remaining cases.

Differential Revision: https://reviews.llvm.org/D97053

Added: 
    

Modified: 
    clang/lib/Sema/SemaChecking.cpp
    clang/test/SemaCXX/attr-arm-sve-vector-bits.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 2d3d36f4adad..b41d94361d50 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -12051,7 +12051,16 @@ static void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
     checkObjCDictionaryLiteral(S, QualType(Target, 0), DictionaryLiteral);
 
   // Strip vector types.
-  if (isa<VectorType>(Source)) {
+  if (const auto *SourceVT = dyn_cast<VectorType>(Source)) {
+    if (Target->isVLSTBuiltinType()) {
+      auto SourceVectorKind = SourceVT->getVectorKind();
+      if (SourceVectorKind == VectorType::SveFixedLengthDataVector ||
+          SourceVectorKind == VectorType::SveFixedLengthPredicateVector ||
+          (SourceVectorKind == VectorType::GenericVector &&
+           S.Context.getTypeSize(Source) == S.getLangOpts().ArmSveVectorBits))
+        return;
+    }
+
     if (!isa<VectorType>(Target)) {
       if (S.SourceMgr.isInSystemMacro(CC))
         return;

diff  --git a/clang/test/SemaCXX/attr-arm-sve-vector-bits.cpp b/clang/test/SemaCXX/attr-arm-sve-vector-bits.cpp
index 5e796b7c8995..0437a264f65b 100644
--- a/clang/test/SemaCXX/attr-arm-sve-vector-bits.cpp
+++ b/clang/test/SemaCXX/attr-arm-sve-vector-bits.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve -target-feature +bf16 -ffreestanding -fsyntax-only -verify -std=c++11 -msve-vector-bits=512 -fallow-half-arguments-and-returns %s
+// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve -target-feature +bf16 -ffreestanding -fsyntax-only -verify -std=c++11 -msve-vector-bits=512 -fallow-half-arguments-and-returns -Wconversion %s
 // expected-no-diagnostics
 
 #include <stdint.h>