[clang,ARM] Initial ACLE intrinsics for MVE.

This commit sets up the infrastructure for auto-generating <arm_mve.h>
and doing clang-side code generation for the builtins it relies on,
and demonstrates that it works by implementing a representative sample
of the ACLE intrinsics, more or less matching the ones introduced in
LLVM IR by D67158,D68699,D68700.

Like NEON, that header file will provide a set of vector types like
uint16x8_t and C functions with names like vaddq_u32(). Unlike NEON,
the ACLE spec for <arm_mve.h> includes a polymorphism system, so that
you can write plain vaddq() and disambiguate by the vector types you
pass to it.

Unlike the corresponding NEON code, I've arranged to make every user-
facing ACLE intrinsic into a clang builtin, and implement all the code
generation inside clang. So <arm_mve.h> itself contains nothing but
typedefs and function declarations, with the latter all using the new
`__attribute__((__clang_builtin))` system to arrange that the user-
facing function names correspond to the right internal BuiltinIDs.

So the new MveEmitter tablegen system specifies the full sequence of
IRBuilder operations that each user-facing ACLE intrinsic should
translate into. Where possible, the ACLE intrinsics map to standard IR
operations such as vector-typed `add` and `fadd`; where no standard
representation exists, I call down to the sample IR intrinsics
introduced in an earlier commit.

Doing it like this means that you get the polymorphism for free just
by using __attribute__((overloadable)): the clang overload resolution
decides which function declaration is the relevant one, and _then_ its
BuiltinID is looked up, so by the time we're doing code generation,
that's all been resolved by the standard system. It also means that
you get really nice error messages if the user passes the wrong
combination of types: clang will show the declarations from the header
file and explain why each one doesn't match.

(The obvious alternative approach would be to have wrapper functions
in <arm_mve.h> which pass their arguments to the underlying builtins.
But that doesn't work in the case where one of the arguments has to be
a constant integer: the wrapper function can't pass the constantness
through. So you'd have to do that case using a macro instead, and then
use C11 `_Generic` to handle the polymorphism. Then you have to add
horrible workarounds because `_Generic` requires even the untaken
branches to type-check successfully, and //then// if the user gets the
types wrong, the error message is totally unreadable!)

Reviewers: dmgreen, miyuki, ostannard

Subscribers: mgorny, javed.absar, kristof.beyls, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67161

1 files changed, 105 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index dca81d1d275..8322a9bf147 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -1717,6 +1717,14 @@ bool Sema::CheckNeonBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
   return SemaBuiltinConstantArgRange(TheCall, i, l, u + l);
 }
 
+bool Sema::CheckMVEBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
+  switch (BuiltinID) {
+  default:
+    return false;
+  #include "clang/Basic/arm_mve_builtin_sema.inc"
+  }
+}
+
 bool Sema::CheckARMBuiltinExclusiveCall(unsigned BuiltinID, CallExpr *TheCall,
                                         unsigned MaxWidth) {
   assert((BuiltinID == ARM::BI__builtin_arm_ldrex ||
@@ -1857,6 +1865,8 @@ bool Sema::CheckARMBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
 
   if (CheckNeonBuiltinFunctionCall(BuiltinID, TheCall))
     return true;
+  if (CheckMVEBuiltinFunctionCall(BuiltinID, TheCall))
+    return true;
 
   // For intrinsics which take an immediate value as part of the instruction,
   // range check them here.
@@ -6235,6 +6245,101 @@ bool Sema::SemaBuiltinConstantArgMultiple(CallExpr *TheCall, int ArgNum,
   return false;
 }
 
+/// SemaBuiltinConstantArgPower2 - Check if argument ArgNum of TheCall is a
+/// constant expression representing a power of 2.
+bool Sema::SemaBuiltinConstantArgPower2(CallExpr *TheCall, int ArgNum) {
+  llvm::APSInt Result;
+
+  // We can't check the value of a dependent argument.
+  Expr *Arg = TheCall->getArg(ArgNum);
+  if (Arg->isTypeDependent() || Arg->isValueDependent())
+    return false;
+
+  // Check constant-ness first.
+  if (SemaBuiltinConstantArg(TheCall, ArgNum, Result))
+    return true;
+
+  // Bit-twiddling to test for a power of 2: for x > 0, x & (x-1) is zero if
+  // and only if x is a power of 2.
+  if (Result.isStrictlyPositive() && (Result & (Result - 1)) == 0)
+    return false;
+
+  return Diag(TheCall->getBeginLoc(), diag::err_argument_not_power_of_2)
+         << Arg->getSourceRange();
+}
+
+static bool IsShiftedByte(llvm::APSInt Value) {
+  if (Value.isNegative())
+    return false;
+
+  // Check if it's a shifted byte, by shifting it down
+  while (true) {
+    // If the value fits in the bottom byte, the check passes.
+    if (Value < 0x100)
+      return true;
+
+    // Otherwise, if the value has _any_ bits in the bottom byte, the check
+    // fails.
+    if ((Value & 0xFF) != 0)
+      return false;
+
+    // If the bottom 8 bits are all 0, but something above that is nonzero,
+    // then shifting the value right by 8 bits won't affect whether it's a
+    // shifted byte or not. So do that, and go round again.
+    Value >>= 8;
+  }
+}
+
+/// SemaBuiltinConstantArgShiftedByte - Check if argument ArgNum of TheCall is
+/// a constant expression representing an arbitrary byte value shifted left by
+/// a multiple of 8 bits.
+bool Sema::SemaBuiltinConstantArgShiftedByte(CallExpr *TheCall, int ArgNum) {
+  llvm::APSInt Result;
+
+  // We can't check the value of a dependent argument.
+  Expr *Arg = TheCall->getArg(ArgNum);
+  if (Arg->isTypeDependent() || Arg->isValueDependent())
+    return false;
+
+  // Check constant-ness first.
+  if (SemaBuiltinConstantArg(TheCall, ArgNum, Result))
+    return true;
+
+  if (IsShiftedByte(Result))
+    return false;
+
+  return Diag(TheCall->getBeginLoc(), diag::err_argument_not_shifted_byte)
+         << Arg->getSourceRange();
+}
+
+/// SemaBuiltinConstantArgShiftedByteOr0xFF - Check if argument ArgNum of
+/// TheCall is a constant expression representing either a shifted byte value,
+/// or a value of the form 0x??FF (i.e. a member of the arithmetic progression
+/// 0x00FF, 0x01FF, ..., 0xFFFF). This strange range check is needed for some
+/// Arm MVE intrinsics.
+bool Sema::SemaBuiltinConstantArgShiftedByteOrXXFF(CallExpr *TheCall,
+                                                   int ArgNum) {
+  llvm::APSInt Result;
+
+  // We can't check the value of a dependent argument.
+  Expr *Arg = TheCall->getArg(ArgNum);
+  if (Arg->isTypeDependent() || Arg->isValueDependent())
+    return false;
+
+  // Check constant-ness first.
+  if (SemaBuiltinConstantArg(TheCall, ArgNum, Result))
+    return true;
+
+  // Check to see if it's in either of the required forms.
+  if (IsShiftedByte(Result) ||
+      (Result > 0 && Result < 0x10000 && (Result & 0xFF) == 0xFF))
+    return false;
+
+  return Diag(TheCall->getBeginLoc(),
+              diag::err_argument_not_shifted_byte_or_xxff)
+         << Arg->getSourceRange();
+}
+
 /// SemaBuiltinARMMemoryTaggingCall - Handle calls of memory tagging extensions
 bool Sema::SemaBuiltinARMMemoryTaggingCall(unsigned BuiltinID, CallExpr *TheCall) {
   if (BuiltinID == AArch64::BI__builtin_arm_irg) {