[InstCombine] Avoid crash on aggregate types in SimplifyDemandedUseFPClass (#111128)

The disables folding for FP aggregates that are not poison/posZero
types, which is currently not supported. Note: To fully handle this
aggregates would also likely require teaching `computeKnownFPClass()` to
handle array and struct constants (which does not seem implemented
outside of zero init).

Author: MacDue

llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp

@@ -1919,17 +1919,23 @@ Value *InstCombinerImpl::SimplifyDemandedVectorElts(Value *V,
 /// For floating-point classes that resolve to a single bit pattern, return that
 /// value.
 static Constant *getFPClassConstant(Type *Ty, FPClassTest Mask) {
+  if (Mask == fcNone)
+    return PoisonValue::get(Ty);
+
+  if (Mask == fcPosZero)
+    return Constant::getNullValue(Ty);
+
+  // TODO: Support aggregate types that are allowed by FPMathOperator.
+  if (Ty->isAggregateType())
+    return nullptr;
+
   switch (Mask) {
-  case fcPosZero:
-    return ConstantFP::getZero(Ty);
   case fcNegZero:
     return ConstantFP::getZero(Ty, true);
   case fcPosInf:
     return ConstantFP::getInfinity(Ty);
   case fcNegInf:
     return ConstantFP::getInfinity(Ty, true);
-  case fcNone:
-    return PoisonValue::get(Ty);
   default:
     return nullptr;
   }

llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll

@@ -91,6 +91,126 @@ define nofpclass(inf) float @ret_nofpclass_inf__ninf() {
   ret float 0xFFF0000000000000
 }
 
+; Basic aggregate tests to ensure this does not crash.
+define nofpclass(nan) { float } @ret_nofpclass_struct_ty() {
+; CHECK-LABEL: define nofpclass(nan) { float } @ret_nofpclass_struct_ty() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { float } zeroinitializer
+;
+entry:
+  ret { float } zeroinitializer
+}
+
+define nofpclass(nan) { float, float } @ret_nofpclass_multiple_elems_struct_ty() {
+; CHECK-LABEL: define nofpclass(nan) { float, float } @ret_nofpclass_multiple_elems_struct_ty() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { float, float } zeroinitializer
+;
+entry:
+  ret { float, float } zeroinitializer
+}
+
+define nofpclass(nan) { <4 x float>, <4 x float> } @ret_nofpclass_vector_elems_struct_ty() {
+; CHECK-LABEL: define nofpclass(nan) { <4 x float>, <4 x float> } @ret_nofpclass_vector_elems_struct_ty() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { <4 x float>, <4 x float> } zeroinitializer
+;
+entry:
+  ret { <4 x float>, <4 x float> } zeroinitializer
+}
+
+define nofpclass(nan) [ 5 x float ] @ret_nofpclass_array_ty() {
+; CHECK-LABEL: define nofpclass(nan) [5 x float] @ret_nofpclass_array_ty() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret [5 x float] zeroinitializer
+;
+entry:
+  ret [ 5 x float ] zeroinitializer
+}
+
+define nofpclass(nan) [ 2 x [ 5 x float ]] @ret_nofpclass_nested_array_ty() {
+; CHECK-LABEL: define nofpclass(nan) [2 x [5 x float]] @ret_nofpclass_nested_array_ty() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret [2 x [5 x float]] zeroinitializer
+;
+entry:
+  ret [ 2 x [ 5 x float ]] zeroinitializer
+}
+
+define nofpclass(pinf) { float } @ret_nofpclass_struct_ty_pinf__ninf() {
+; CHECK-LABEL: define nofpclass(pinf) { float } @ret_nofpclass_struct_ty_pinf__ninf() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { float } { float 0xFFF0000000000000 }
+;
+entry:
+  ret { float } { float 0xFFF0000000000000 }
+}
+
+define nofpclass(pinf) { float, float } @ret_nofpclass_multiple_elems_struct_ty_pinf__ninf() {
+; CHECK-LABEL: define nofpclass(pinf) { float, float } @ret_nofpclass_multiple_elems_struct_ty_pinf__ninf() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { float, float } { float 0xFFF0000000000000, float 0xFFF0000000000000 }
+;
+entry:
+  ret { float, float } { float 0xFFF0000000000000, float 0xFFF0000000000000 }
+}
+
+define nofpclass(pinf) { <2 x float> } @ret_nofpclass_vector_elems_struct_ty_pinf__ninf() {
+; CHECK-LABEL: define nofpclass(pinf) { <2 x float> } @ret_nofpclass_vector_elems_struct_ty_pinf__ninf() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { <2 x float> } { <2 x float> <float 0xFFF0000000000000, float 0xFFF0000000000000> }
+;
+entry:
+  ret { <2 x float>} { <2 x float> <float 0xFFF0000000000000, float 0xFFF0000000000000> }
+}
+
+define nofpclass(pinf) [ 1 x [ 1 x float ]] @ret_nofpclass_nested_array_ty_pinf__ninf() {
+; CHECK-LABEL: @ret_nofpclass_nested_array_ty_pinf__ninf() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret {{.*}}float 0xFFF0000000000000
+;
+entry:
+  ret [ 1 x [ 1 x float ]] [[ 1 x float ] [float 0xFFF0000000000000]]
+}
+
+define nofpclass(pzero) { float, float } @ret_nofpclass_multiple_elems_struct_ty_pzero__nzero() {
+; CHECK-LABEL: define nofpclass(pzero) { float, float } @ret_nofpclass_multiple_elems_struct_ty_pzero__nzero() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { float, float } { float -0.000000e+00, float -0.000000e+00 }
+;
+entry:
+  ret { float, float } { float -0.0, float -0.0 }
+}
+
+define nofpclass(ninf) { float, float } @ret_nofpclass_multiple_elems_struct_ty_ninf__npinf() {
+; CHECK-LABEL: define nofpclass(ninf) { float, float } @ret_nofpclass_multiple_elems_struct_ty_ninf__npinf() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { float, float } { float 0x7FF0000000000000, float 0x7FF0000000000000 }
+;
+entry:
+  ret { float, float } { float 0x7FF0000000000000, float 0x7FF0000000000000 }
+}
+
+; FIXME (should be poison): Support computeKnownFPClass() for non-zero aggregates.
+define nofpclass(inf) { float, float } @ret_nofpclass_multiple_elems_struct_ty_inf__npinf() {
+; CHECK-LABEL: define nofpclass(inf) { float, float } @ret_nofpclass_multiple_elems_struct_ty_inf__npinf() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret { float, float } { float 0x7FF0000000000000, float 0x7FF0000000000000 }
+;
+entry:
+  ret { float, float } { float 0x7FF0000000000000, float 0x7FF0000000000000 }
+}
+
+; FIXME (should be poison): Support computeKnownFPClass() for non-zero aggregates.
+define nofpclass(nzero) [ 1 x float ] @ret_nofpclass_multiple_elems_struct_ty_nzero_nzero() {
+; CHECK-LABEL: define nofpclass(nzero) [1 x float] @ret_nofpclass_multiple_elems_struct_ty_nzero_nzero() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    ret [1 x float] [float -0.000000e+00]
+;
+entry:
+  ret [ 1 x float ] [ float -0.0 ]
+}
+
 ; Negative test, do nothing
 define nofpclass(inf) float @ret_nofpclass_inf__select_nofpclass_inf_lhs(i1 %cond, float nofpclass(inf) %x, float %y) {
 ; CHECK-LABEL: define nofpclass(inf) float @ret_nofpclass_inf__select_nofpclass_inf_lhs