[ValueTypes] Add EVT::isFixedLengthVector

Summary:
Related to D75672, this patch adds EVT::isFixedLengthVector to determine
if the underlying vector type is of fixed length.

An assert is introduced in EVT::getVectorNumElements that triggers for
types that aren't fixed length. This is currently guarded by a flag
added D75297 that is off by default and has been renamed to the more
generic ENABLE_STRICT_FIXED_SIZE_VECTORS.

Ideally we want to get rid of getVectorNumElements but a quick grep
shows there are >350 uses in lib/CodeGen and 75 in lib/Target/AArch64
alone. All of these probably aren't EVT::getVectorNumElements (some may
be the MVT equivalent), but there are many places to fixup and having
the assert on by default would make the SVE upstreaming effort
difficult.

Reviewers: sdesmalen, efriedma, ctetreau, huntergr, rengolin

Reviewed By: efriedma

Subscribers: mgorny, kristof.beyls, hiraditya, danielkiss, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76376

llvm/CMakeLists.txt

@@ -418,7 +418,7 @@ option(LLVM_ENABLE_EXPENSIVE_CHECKS "Enable expensive checks" OFF)
 # Enabling this flag makes it easier to find cases where the compiler makes
 # assumptions on the size being 'fixed size', when building tests for
 # SVE/SVE2 or other scalable vector architectures.
-option(LLVM_ENABLE_STRICT_IMPLICIT_CONVERSION_TYPESIZE
+option(LLVM_ENABLE_STRICT_FIXED_SIZE_VECTORS
        "Enable assertions that type is not scalable in implicit conversion from TypeSize to uint64_t" OFF)
 
 set(LLVM_ABI_BREAKING_CHECKS "WITH_ASSERTS" CACHE STRING

llvm/cmake/modules/HandleLLVMOptions.cmake

@@ -95,8 +95,8 @@ if(LLVM_ENABLE_EXPENSIVE_CHECKS)
   endif()
 endif()
 
-if (LLVM_ENABLE_STRICT_IMPLICIT_CONVERSION_TYPESIZE)
-  add_definitions(-DSTRICT_IMPLICIT_CONVERSION_TYPESIZE)
+if (LLVM_ENABLE_STRICT_FIXED_SIZE_VECTORS)
+  add_definitions(-DSTRICT_FIXED_SIZE_VECTORS)
 endif()
 
 string(TOUPPER "${LLVM_ABI_BREAKING_CHECKS}" uppercase_LLVM_ABI_BREAKING_CHECKS)

llvm/include/llvm/CodeGen/ValueTypes.h

@@ -19,6 +19,7 @@
 #include "llvm/Support/MachineValueType.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/TypeSize.h"
+#include "llvm/Support/WithColor.h"
 #include <cassert>
 #include <cstdint>
 #include <string>
@@ -163,6 +164,11 @@ namespace llvm {
       return V.isScalableVector();
     }
 
+    bool isFixedLengthVector() const {
+      return isSimple() ? V.isFixedLengthVector()
+                        : isExtendedFixedLengthVector();
+    }
+
     /// Return true if this is a 16-bit vector type.
     bool is16BitVector() const {
       return isSimple() ? V.is16BitVector() : isExtended16BitVector();
@@ -273,7 +279,16 @@ namespace llvm {
 
     /// Given a vector type, return the number of elements it contains.
     unsigned getVectorNumElements() const {
+#ifdef STRICT_FIXED_SIZE_VECTORS
+      assert(isFixedLengthVector() && "Invalid vector type!");
+#else
       assert(isVector() && "Invalid vector type!");
+      if (isScalableVector())
+        WithColor::warning()
+            << "Possible incorrect use of EVT::getVectorNumElements() for "
+               "scalable vector. Scalable flag may be dropped, use"
+               "EVT::getVectorElementCount() instead\n";
+#endif
       if (isSimple())
         return V.getVectorNumElements();
       return getExtendedVectorNumElements();
@@ -442,6 +457,7 @@ namespace llvm {
     bool isExtended512BitVector() const LLVM_READONLY;
     bool isExtended1024BitVector() const LLVM_READONLY;
     bool isExtended2048BitVector() const LLVM_READONLY;
+    bool isExtendedFixedLengthVector() const LLVM_READONLY;
     EVT getExtendedVectorElementType() const;
     unsigned getExtendedVectorNumElements() const LLVM_READONLY;
     TypeSize getExtendedSizeInBits() const LLVM_READONLY;

llvm/include/llvm/Support/TypeSize.h

@@ -165,7 +165,7 @@ public:
   //       bail out early for scalable vectors and use getFixedSize()
   //   }
   operator uint64_t() const {
-#ifdef STRICT_IMPLICIT_CONVERSION_TYPESIZE
+#ifdef STRICT_FIXED_SIZE_VECTORS
     return getFixedSize();
 #else
     if (isScalable())

llvm/lib/CodeGen/ValueTypes.cpp

@@ -92,6 +92,10 @@ bool EVT::isExtended2048BitVector() const {
   return isExtendedVector() && getExtendedSizeInBits() == 2048;
 }
 
+bool EVT::isExtendedFixedLengthVector() const {
+  return isExtendedVector() && !cast<VectorType>(LLVMTy)->isScalable();
+}
+
 EVT EVT::getExtendedVectorElementType() const {
   assert(isExtended() && "Type is not extended!");
   return EVT::getEVT(cast<VectorType>(LLVMTy)->getElementType());