Fix convertBFloatAPFloatToAPInt for NaN/Inf values

Bfloat type has an 8-bit exponent so the exponent of NaN/Inf numbers
must be 0xff instead of 0x1f. This is probably a copy-paste mistake
from the half float type.

Reviewed By: lattner

Differential Revision: https://reviews.llvm.org/D81302

llvm/lib/Support/APFloat.cpp

@@ -3278,11 +3278,11 @@ APInt IEEEFloat::convertBFloatAPFloatToAPInt() const {
     myexponent = 0;
     mysignificand = 0;
   } else if (category == fcInfinity) {
-    myexponent = 0x1f;
+    myexponent = 0xff;
     mysignificand = 0;
   } else {
     assert(category == fcNaN && "Unknown category!");
-    myexponent = 0x1f;
+    myexponent = 0xff;
     mysignificand = (uint32_t)*significandParts();
   }
 

llvm/test/Assembler/bfloat.ll

@@ -36,3 +36,27 @@ define float @check_bfloat_convert() {
 ; OPT: 0x4191A00000000000
   ret float %tmp
 }
+
+; ASSEM-DISASS-LABEL @snan_bfloat
+define bfloat @snan_bfloat() {
+; ASSEM-DISASS: ret bfloat 0xR7F81
+    ret bfloat 0xR7F81
+}
+
+; ASSEM-DISASS-LABEL @qnan_bfloat
+define bfloat @qnan_bfloat() {
+; ASSEM-DISASS: ret bfloat 0xR7FC0
+    ret bfloat 0xR7FC0
+}
+
+; ASSEM-DISASS-LABEL @pos_inf_bfloat
+define bfloat @pos_inf_bfloat() {
+; ASSEM-DISASS: ret bfloat 0xR7F80
+    ret bfloat 0xR7F80
+}
+
+; ASSEM-DISASS-LABEL @neg_inf_bfloat
+define bfloat @neg_inf_bfloat() {
+; ASSEM-DISASS: ret bfloat 0xRFF80
+    ret bfloat 0xRFF80
+}