Revert "Reland "Reland "[X86][RFC] Enable _Float16 type support on X86 following the psABI"""

This reverts commit e1c5afa.

This introduces crashes in the JAX backend on CPU. A reproducer in LLVM is
below. Let me know if you have trouble reproducing this.

; ModuleID = '__compute_module'
source_filename = "__compute_module"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-grtev4-linux-gnu"

@0 = private unnamed_addr constant [4 x i8] c"\00\00\00?"
@1 = private unnamed_addr constant [4 x i8] c"\1C}\908"
@2 = private unnamed_addr constant [4 x i8] c"?\00\\4"
@3 = private unnamed_addr constant [4 x i8] c"%ci1"
@4 = private unnamed_addr constant [4 x i8] zeroinitializer
@5 = private unnamed_addr constant [4 x i8] c"\00\00\00\C0"
@6 = private unnamed_addr constant [4 x i8] c"\00\00\00B"
@7 = private unnamed_addr constant [4 x i8] c"\94\B4\C22"
@8 = private unnamed_addr constant [4 x i8] c"^\09B6"
@9 = private unnamed_addr constant [4 x i8] c"\15\F3M?"
@10 = private unnamed_addr constant [4 x i8] c"e\CC\\;"
@11 = private unnamed_addr constant [4 x i8] c"d\BD/>"
@12 = private unnamed_addr constant [4 x i8] c"V\F4I="
@13 = private unnamed_addr constant [4 x i8] c"\10\CB,<"
@14 = private unnamed_addr constant [4 x i8] c"\AC\E3\D6:"
@15 = private unnamed_addr constant [4 x i8] c"\DC\A8E9"
@16 = private unnamed_addr constant [4 x i8] c"\C6\FA\897"
@17 = private unnamed_addr constant [4 x i8] c"%\F9\955"
@18 = private unnamed_addr constant [4 x i8] c"\B5\DB\813"
@19 = private unnamed_addr constant [4 x i8] c"\B4W_\B2"
@20 = private unnamed_addr constant [4 x i8] c"\1Cc\8F\B4"
@21 = private unnamed_addr constant [4 x i8] c"~3\94\B6"
@22 = private unnamed_addr constant [4 x i8] c"3Yq\B8"
@23 = private unnamed_addr constant [4 x i8] c"\E9\17\17\BA"
@24 = private unnamed_addr constant [4 x i8] c"\F1\B2\8D\BB"
@25 = private unnamed_addr constant [4 x i8] c"\F8t\C2\BC"
@26 = private unnamed_addr constant [4 x i8] c"\82[\C2\BD"
@27 = private unnamed_addr constant [4 x i8] c"uB-?"
@28 = private unnamed_addr constant [4 x i8] c"^\FF\9B\BE"
@29 = private unnamed_addr constant [4 x i8] c"\00\00\00A"

; Function Attrs: uwtable
define void @main.158(ptr %retval, ptr noalias %run_options, ptr noalias %params, ptr noalias %buffer_table, ptr noalias %status, ptr noalias %prof_counters) #0 {
entry:
  %fusion.invar_address.dim.1 = alloca i64, align 8
  %fusion.invar_address.dim.0 = alloca i64, align 8
  %0 = getelementptr inbounds ptr, ptr %buffer_table, i64 1
  %Arg_0.1 = load ptr, ptr %0, align 8, !invariant.load !0, !dereferenceable !1, !align !2
  %1 = getelementptr inbounds ptr, ptr %buffer_table, i64 0
  %fusion = load ptr, ptr %1, align 8, !invariant.load !0, !dereferenceable !1, !align !2
  store i64 0, ptr %fusion.invar_address.dim.0, align 8
  br label %fusion.loop_header.dim.0

return:                                           ; preds = %fusion.loop_exit.dim.0
  ret void

fusion.loop_header.dim.0:                         ; preds = %fusion.loop_exit.dim.1, %entry
  %fusion.indvar.dim.0 = load i64, ptr %fusion.invar_address.dim.0, align 8
  %2 = icmp uge i64 %fusion.indvar.dim.0, 3
  br i1 %2, label %fusion.loop_exit.dim.0, label %fusion.loop_body.dim.0

fusion.loop_body.dim.0:                           ; preds = %fusion.loop_header.dim.0
  store i64 0, ptr %fusion.invar_address.dim.1, align 8
  br label %fusion.loop_header.dim.1

fusion.loop_header.dim.1:                         ; preds = %fusion.loop_body.dim.1, %fusion.loop_body.dim.0
  %fusion.indvar.dim.1 = load i64, ptr %fusion.invar_address.dim.1, align 8
  %3 = icmp uge i64 %fusion.indvar.dim.1, 1
  br i1 %3, label %fusion.loop_exit.dim.1, label %fusion.loop_body.dim.1

fusion.loop_body.dim.1:                           ; preds = %fusion.loop_header.dim.1
  %4 = getelementptr inbounds [3 x [1 x half]], ptr %Arg_0.1, i64 0, i64 %fusion.indvar.dim.0, i64 0
  %5 = load half, ptr %4, align 2, !invariant.load !0, !noalias !3
  %6 = fpext half %5 to float
  %7 = call float @llvm.fabs.f32(float %6)
  %constant.121 = load float, ptr @29, align 4
  %compare.2 = fcmp ole float %7, %constant.121
  %8 = zext i1 %compare.2 to i8
  %constant.120 = load float, ptr @0, align 4
  %multiply.95 = fmul float %7, %constant.120
  %constant.119 = load float, ptr @5, align 4
  %add.82 = fadd float %multiply.95, %constant.119
  %constant.118 = load float, ptr @4, align 4
  %multiply.94 = fmul float %add.82, %constant.118
  %constant.117 = load float, ptr @19, align 4
  %add.81 = fadd float %multiply.94, %constant.117
  %multiply.92 = fmul float %add.82, %add.81
  %constant.116 = load float, ptr @18, align 4
  %add.79 = fadd float %multiply.92, %constant.116
  %multiply.91 = fmul float %add.82, %add.79
  %subtract.87 = fsub float %multiply.91, %add.81
  %constant.115 = load float, ptr @20, align 4
  %add.78 = fadd float %subtract.87, %constant.115
  %multiply.89 = fmul float %add.82, %add.78
  %subtract.86 = fsub float %multiply.89, %add.79
  %constant.114 = load float, ptr @17, align 4
  %add.76 = fadd float %subtract.86, %constant.114
  %multiply.88 = fmul float %add.82, %add.76
  %subtract.84 = fsub float %multiply.88, %add.78
  %constant.113 = load float, ptr @21, align 4
  %add.75 = fadd float %subtract.84, %constant.113
  %multiply.86 = fmul float %add.82, %add.75
  %subtract.83 = fsub float %multiply.86, %add.76
  %constant.112 = load float, ptr @16, align 4
  %add.73 = fadd float %subtract.83, %constant.112
  %multiply.85 = fmul float %add.82, %add.73
  %subtract.81 = fsub float %multiply.85, %add.75
  %constant.111 = load float, ptr @22, align 4
  %add.72 = fadd float %subtract.81, %constant.111
  %multiply.83 = fmul float %add.82, %add.72
  %subtract.80 = fsub float %multiply.83, %add.73
  %constant.110 = load float, ptr @15, align 4
  %add.70 = fadd float %subtract.80, %constant.110
  %multiply.82 = fmul float %add.82, %add.70
  %subtract.78 = fsub float %multiply.82, %add.72
  %constant.109 = load float, ptr @23, align 4
  %add.69 = fadd float %subtract.78, %constant.109
  %multiply.80 = fmul float %add.82, %add.69
  %subtract.77 = fsub float %multiply.80, %add.70
  %constant.108 = load float, ptr @14, align 4
  %add.68 = fadd float %subtract.77, %constant.108
  %multiply.79 = fmul float %add.82, %add.68
  %subtract.75 = fsub float %multiply.79, %add.69
  %constant.107 = load float, ptr @24, align 4
  %add.67 = fadd float %subtract.75, %constant.107
  %multiply.77 = fmul float %add.82, %add.67
  %subtract.74 = fsub float %multiply.77, %add.68
  %constant.106 = load float, ptr @13, align 4
  %add.66 = fadd float %subtract.74, %constant.106
  %multiply.76 = fmul float %add.82, %add.66
  %subtract.72 = fsub float %multiply.76, %add.67
  %constant.105 = load float, ptr @25, align 4
  %add.65 = fadd float %subtract.72, %constant.105
  %multiply.74 = fmul float %add.82, %add.65
  %subtract.71 = fsub float %multiply.74, %add.66
  %constant.104 = load float, ptr @12, align 4
  %add.64 = fadd float %subtract.71, %constant.104
  %multiply.73 = fmul float %add.82, %add.64
  %subtract.69 = fsub float %multiply.73, %add.65
  %constant.103 = load float, ptr @26, align 4
  %add.63 = fadd float %subtract.69, %constant.103
  %multiply.71 = fmul float %add.82, %add.63
  %subtract.67 = fsub float %multiply.71, %add.64
  %constant.102 = load float, ptr @11, align 4
  %add.62 = fadd float %subtract.67, %constant.102
  %multiply.70 = fmul float %add.82, %add.62
  %subtract.66 = fsub float %multiply.70, %add.63
  %constant.101 = load float, ptr @28, align 4
  %add.61 = fadd float %subtract.66, %constant.101
  %multiply.68 = fmul float %add.82, %add.61
  %subtract.65 = fsub float %multiply.68, %add.62
  %constant.100 = load float, ptr @27, align 4
  %add.60 = fadd float %subtract.65, %constant.100
  %subtract.64 = fsub float %add.60, %add.62
  %multiply.66 = fmul float %subtract.64, %constant.120
  %constant.99 = load float, ptr @6, align 4
  %divide.4 = fdiv float %constant.99, %7
  %add.59 = fadd float %divide.4, %constant.119
  %multiply.65 = fmul float %add.59, %constant.118
  %constant.98 = load float, ptr @3, align 4
  %add.58 = fadd float %multiply.65, %constant.98
  %multiply.64 = fmul float %add.59, %add.58
  %constant.97 = load float, ptr @7, align 4
  %add.57 = fadd float %multiply.64, %constant.97
  %multiply.63 = fmul float %add.59, %add.57
  %subtract.63 = fsub float %multiply.63, %add.58
  %constant.96 = load float, ptr @2, align 4
  %add.56 = fadd float %subtract.63, %constant.96
  %multiply.62 = fmul float %add.59, %add.56
  %subtract.62 = fsub float %multiply.62, %add.57
  %constant.95 = load float, ptr @8, align 4
  %add.55 = fadd float %subtract.62, %constant.95
  %multiply.61 = fmul float %add.59, %add.55
  %subtract.61 = fsub float %multiply.61, %add.56
  %constant.94 = load float, ptr @1, align 4
  %add.54 = fadd float %subtract.61, %constant.94
  %multiply.60 = fmul float %add.59, %add.54
  %subtract.60 = fsub float %multiply.60, %add.55
  %constant.93 = load float, ptr @10, align 4
  %add.53 = fadd float %subtract.60, %constant.93
  %multiply.59 = fmul float %add.59, %add.53
  %subtract.59 = fsub float %multiply.59, %add.54
  %constant.92 = load float, ptr @9, align 4
  %add.52 = fadd float %subtract.59, %constant.92
  %subtract.58 = fsub float %add.52, %add.54
  %multiply.58 = fmul float %subtract.58, %constant.120
  %9 = call float @llvm.sqrt.f32(float %7)
  %10 = fdiv float 1.000000e+00, %9
  %multiply.57 = fmul float %multiply.58, %10
  %11 = trunc i8 %8 to i1
  %12 = select i1 %11, float %multiply.66, float %multiply.57
  %13 = fptrunc float %12 to half
  %14 = getelementptr inbounds [3 x [1 x half]], ptr %fusion, i64 0, i64 %fusion.indvar.dim.0, i64 0
  store half %13, ptr %14, align 2, !alias.scope !3
  %invar.inc1 = add nuw nsw i64 %fusion.indvar.dim.1, 1
  store i64 %invar.inc1, ptr %fusion.invar_address.dim.1, align 8
  br label %fusion.loop_header.dim.1

fusion.loop_exit.dim.1:                           ; preds = %fusion.loop_header.dim.1
  %invar.inc = add nuw nsw i64 %fusion.indvar.dim.0, 1
  store i64 %invar.inc, ptr %fusion.invar_address.dim.0, align 8
  br label %fusion.loop_header.dim.0

fusion.loop_exit.dim.0:                           ; preds = %fusion.loop_header.dim.0
  br label %return
}

; Function Attrs: nocallback nofree nosync nounwind readnone speculatable willreturn
declare float @llvm.fabs.f32(float %0) #1

; Function Attrs: nocallback nofree nosync nounwind readnone speculatable willreturn
declare float @llvm.sqrt.f32(float %0) #1

attributes #0 = { uwtable "denormal-fp-math"="preserve-sign" "no-frame-pointer-elim"="false" }
attributes #1 = { nocallback nofree nosync nounwind readnone speculatable willreturn }

!0 = !{}
!1 = !{i64 6}
!2 = !{i64 8}
!3 = !{!4}
!4 = !{!"buffer: {index:0, offset:0, size:6}", !5}
!5 = !{!"XLA global AA domain"}

Author: frgossen

llvm/docs/ReleaseNotes.rst

@@ -138,7 +138,7 @@ Changes to the WebAssembly Backend
 Changes to the X86 Backend
 --------------------------
 
-* Support ``half`` type on SSE2 and above targets.
+* ...
 
 Changes to the OCaml bindings
 -----------------------------

llvm/lib/Target/X86/X86FastISel.cpp

@@ -148,7 +148,8 @@ class X86FastISel final : public FastISel {
   /// computed in an SSE register, not on the X87 floating point stack.
   bool isScalarFPTypeInSSEReg(EVT VT) const {
     return (VT == MVT::f64 && Subtarget->hasSSE2()) ||
-           (VT == MVT::f32 && Subtarget->hasSSE1()) || VT == MVT::f16;
+           (VT == MVT::f32 && Subtarget->hasSSE1()) ||
+           (VT == MVT::f16 && Subtarget->hasFP16());
   }
 
   bool isTypeLegal(Type *Ty, MVT &VT, bool AllowI1 = false);
@@ -2280,13 +2281,12 @@ bool X86FastISel::X86FastEmitPseudoSelect(MVT RetVT, const Instruction *I) {
   default: return false;
   case MVT::i8:  Opc = X86::CMOV_GR8;   break;
   case MVT::i16: Opc = X86::CMOV_GR16;  break;
+  case MVT::f16: Opc = X86::CMOV_FR16X; break;
   case MVT::i32: Opc = X86::CMOV_GR32;  break;
-  case MVT::f16:
-    Opc = Subtarget->hasAVX512() ? X86::CMOV_FR16X : X86::CMOV_FR16; break;
-  case MVT::f32:
-    Opc = Subtarget->hasAVX512() ? X86::CMOV_FR32X : X86::CMOV_FR32; break;
-  case MVT::f64:
-    Opc = Subtarget->hasAVX512() ? X86::CMOV_FR64X : X86::CMOV_FR64; break;
+  case MVT::f32: Opc = Subtarget->hasAVX512() ? X86::CMOV_FR32X
+                                              : X86::CMOV_FR32; break;
+  case MVT::f64: Opc = Subtarget->hasAVX512() ? X86::CMOV_FR64X
+                                              : X86::CMOV_FR64; break;
   }
 
   const Value *Cond = I->getOperand(0);
@@ -3903,9 +3903,6 @@ unsigned X86FastISel::fastMaterializeFloatZero(const ConstantFP *CF) {
   unsigned Opc = 0;
   switch (VT.SimpleTy) {
   default: return 0;
-  case MVT::f16:
-    Opc = HasAVX512 ? X86::AVX512_FsFLD0SH : X86::FsFLD0SH;
-    break;
   case MVT::f32:
     Opc = HasAVX512 ? X86::AVX512_FsFLD0SS
           : HasSSE1 ? X86::FsFLD0SS