[NVPTX] Remove nvvm.bitcast.* intrinsics (#107936)

Remove the following intrinsics which correspond directly to a bitcast:

- llvm.nvvm.bitcast.f2i
- llvm.nvvm.bitcast.i2f
- llvm.nvvm.bitcast.d2ll
- llvm.nvvm.bitcast.ll2d

Author: AlexMaclean

clang/include/clang/Basic/BuiltinsNVPTX.def

@@ -599,14 +599,6 @@ TARGET_BUILTIN(__nvvm_e4m3x2_to_f16x2_rn_relu, "V2hs", "", AND(SM_89,PTX81))
 TARGET_BUILTIN(__nvvm_e5m2x2_to_f16x2_rn, "V2hs", "", AND(SM_89,PTX81))
 TARGET_BUILTIN(__nvvm_e5m2x2_to_f16x2_rn_relu, "V2hs", "", AND(SM_89,PTX81))
 
-// Bitcast
-
-BUILTIN(__nvvm_bitcast_f2i, "if", "")
-BUILTIN(__nvvm_bitcast_i2f, "fi", "")
-
-BUILTIN(__nvvm_bitcast_ll2d, "dLLi", "")
-BUILTIN(__nvvm_bitcast_d2ll, "LLid", "")
-
 // FNS
 TARGET_BUILTIN(__nvvm_fns, "UiUiUii", "n", PTX60)
 

llvm/docs/ReleaseNotes.rst

@@ -56,6 +56,13 @@ Changes to the LLVM IR
 
 * Added ``usub_cond`` and ``usub_sat`` operations to ``atomicrmw``.
 
+* Remove the following intrinsics which can be replaced with a ``bitcast``:
+
+  * ``llvm.nvvm.bitcast.f2i``
+  * ``llvm.nvvm.bitcast.i2f``
+  * ``llvm.nvvm.bitcast.d2ll``
+  * ``llvm.nvvm.bitcast.ll2d``
+
 Changes to LLVM infrastructure
 ------------------------------
 

llvm/include/llvm/IR/IntrinsicsNVVM.td

@@ -30,6 +30,10 @@
 //   * llvm.nvvm.max.ui  --> select(x ule y, x, y)
 //   * llvm.nvvm.max.ull --> ibid.
 //   * llvm.nvvm.h2f     --> llvm.convert.to.fp16.f32
+//   * llvm.nvvm.bitcast.f2i  --> bitcast
+//   * llvm.nvvm.bitcast.i2f  --> ibid.
+//   * llvm.nvvm.bitcast.d2ll --> ibid.
+//   * llvm.nvvm.bitcast.ll2d --> ibid.
 
 def llvm_global_ptr_ty  : LLVMQualPointerType<1>;  // (global)ptr
 def llvm_shared_ptr_ty  : LLVMQualPointerType<3>;  // (shared)ptr
@@ -1339,20 +1343,6 @@ let TargetPrefix = "nvvm" in {
   def int_nvvm_e5m2x2_to_f16x2_rn_relu : ClangBuiltin<"__nvvm_e5m2x2_to_f16x2_rn_relu">,
       Intrinsic<[llvm_v2f16_ty], [llvm_i16_ty], [IntrNoMem, IntrNoCallback]>;
 
-//
-// Bitcast
-//
-
-  def int_nvvm_bitcast_f2i : ClangBuiltin<"__nvvm_bitcast_f2i">,
-      DefaultAttrsIntrinsic<[llvm_i32_ty], [llvm_float_ty], [IntrNoMem, IntrSpeculatable]>;
-  def int_nvvm_bitcast_i2f : ClangBuiltin<"__nvvm_bitcast_i2f">,
-      DefaultAttrsIntrinsic<[llvm_float_ty], [llvm_i32_ty], [IntrNoMem, IntrSpeculatable]>;
-
-  def int_nvvm_bitcast_ll2d : ClangBuiltin<"__nvvm_bitcast_ll2d">,
-      DefaultAttrsIntrinsic<[llvm_double_ty], [llvm_i64_ty], [IntrNoMem, IntrSpeculatable]>;
-  def int_nvvm_bitcast_d2ll : ClangBuiltin<"__nvvm_bitcast_d2ll">,
-      DefaultAttrsIntrinsic<[llvm_i64_ty], [llvm_double_ty], [IntrNoMem, IntrSpeculatable]>;
-
 // FNS
 
   def int_nvvm_fns : ClangBuiltin<"__nvvm_fns">,

llvm/lib/IR/AutoUpgrade.cpp

@@ -1268,6 +1268,10 @@ static bool upgradeIntrinsicFunction1(Function *F, Function *&NewFn,
       else if (Name.consume_front("atomic.load.add."))
         // nvvm.atomic.load.add.{f32.p,f64.p}
         Expand = Name.starts_with("f32.p") || Name.starts_with("f64.p");
+      else if (Name.consume_front("bitcast."))
+        // nvvm.bitcast.{f2i,i2f,ll2d,d2ll}
+        Expand =
+            Name == "f2i" || Name == "i2f" || Name == "ll2d" || Name == "d2ll";
       else
         Expand = false;
 
@@ -4258,6 +4262,10 @@ void llvm::UpgradeIntrinsicCall(CallBase *CI, Function *NewFn) {
                                    F->getParent(), Intrinsic::convert_from_fp16,
                                    {Builder.getFloatTy()}),
                                CI->getArgOperand(0), "h2f");
+      } else if (Name.consume_front("bitcast.") &&
+                 (Name == "f2i" || Name == "i2f" || Name == "ll2d" ||
+                  Name == "d2ll")) {
+        Rep = Builder.CreateBitCast(CI->getArgOperand(0), CI->getType());
       } else {
         Intrinsic::ID IID = shouldUpgradeNVPTXBF16Intrinsic(Name);
         if (IID != Intrinsic::not_intrinsic &&

llvm/lib/Target/NVPTX/NVPTXIntrinsics.td

@@ -1577,20 +1577,6 @@ def : Pat<(int_nvvm_e5m2x2_to_f16x2_rn Int16Regs:$a),
 def : Pat<(int_nvvm_e5m2x2_to_f16x2_rn_relu Int16Regs:$a),
           (CVT_f16x2_e5m2x2 Int16Regs:$a, CvtRN_RELU)>;
 
-//
-// Bitcast
-//
-
-def INT_NVVM_BITCAST_F2I : F_MATH_1<"mov.b32 \t$dst, $src0;", Int32Regs,
-  Float32Regs, int_nvvm_bitcast_f2i>;
-def INT_NVVM_BITCAST_I2F : F_MATH_1<"mov.b32 \t$dst, $src0;", Float32Regs,
-  Int32Regs, int_nvvm_bitcast_i2f>;
-
-def INT_NVVM_BITCAST_LL2D : F_MATH_1<"mov.b64 \t$dst, $src0;", Float64Regs,
-  Int64Regs, int_nvvm_bitcast_ll2d>;
-def INT_NVVM_BITCAST_D2LL : F_MATH_1<"mov.b64 \t$dst, $src0;", Int64Regs,
-  Float64Regs, int_nvvm_bitcast_d2ll>;
-
 //
 // FNS
 //

llvm/test/Assembler/auto_upgrade_nvvm_intrinsics.ll

@@ -26,6 +26,11 @@ declare i16 @llvm.nvvm.min.us(i16, i16)
 declare i32 @llvm.nvvm.min.ui(i32, i32)
 declare i64 @llvm.nvvm.min.ull(i64, i64)
 
+declare i32 @llvm.nvvm.bitcast.f2i(float)
+declare float @llvm.nvvm.bitcast.i2f(i32)
+declare i64 @llvm.nvvm.bitcast.d2ll(double)
+declare double @llvm.nvvm.bitcast.ll2d(i64)
+
 ; CHECK-LABEL: @simple_upgrade
 define void @simple_upgrade(i32 %a, i64 %b, i16 %c) {
 ; CHECK: call i32 @llvm.bitreverse.i32(i32 %a)
@@ -120,3 +125,18 @@ define void @min_max(i16 %a1, i16 %a2, i32 %b1, i32 %b2, i64 %c1, i64 %c2) {
 
   ret void
 }
+
+; CHECK-LABEL: @bitcast
+define void @bitcast(i32 %a, i64 %b, float %c, double %d) {
+; CHECK: bitcast float %c to i32
+; CHECK: bitcast i32 %a to float
+; CHECK: bitcast double %d to i64
+; CHECK: bitcast i64 %b to double
+;
+  %r1 = call i32 @llvm.nvvm.bitcast.f2i(float %c)
+  %r2 = call float @llvm.nvvm.bitcast.i2f(i32 %a)
+  %r3 = call i64 @llvm.nvvm.bitcast.d2ll(double %d)
+  %r4 = call double @llvm.nvvm.bitcast.ll2d(i64 %b)
+
+  ret void
+}