Index: llvm/lib/Transforms/Scalar/SCCP.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SCCP.cpp
+++ llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -173,12 +173,14 @@
 
   Instruction *NewInst = nullptr;
   switch (Inst.getOpcode()) {
-  case Instruction::SExt: {
-    // If the source value is not negative, this is a zext.
+  case Instruction::SExt:
+  case Instruction::SIToFP: {
+    // If the source value is not negative, this is an unsigned cast.
     Value *Op0 = Inst.getOperand(0);
-    if (isa<Constant>(Op0) || InsertedValues.count(Op0) || !isNonNegative(Op0))
+    if (InsertedValues.count(Op0) || !isNonNegative(Op0))
       return false;
-    NewInst = new ZExtInst(Op0, Inst.getType(), "", &Inst);
+    auto NewOpcode = Inst.getOpcode() == Inst.SExt ? Inst.ZExt : Inst.UIToFP;
+    NewInst = CastInst::Create(NewOpcode, Op0, Inst.getType(), "", &Inst);
     break;
   }
   case Instruction::AShr: {
Index: llvm/test/Transforms/SCCP/ip-ranges-casts.ll
===================================================================
--- llvm/test/Transforms/SCCP/ip-ranges-casts.ll
+++ llvm/test/Transforms/SCCP/ip-ranges-casts.ll
@@ -160,10 +160,11 @@
   ret i1 %res
 }
 
-; There's nothing we can do besides going to the full range or overdefined.
+; The initial cast is known to only be used with positive values, so it becomes unsigned.
+
 define internal i1 @f.fptosi(i32 %x) {
 ; CHECK-LABEL: @f.fptosi(
-; CHECK-NEXT:    [[TO_DOUBLE:%.*]] = sitofp i32 [[X:%.*]] to double
+; CHECK-NEXT:    [[TO_DOUBLE:%.*]] = uitofp i32 [[X:%.*]] to double
 ; CHECK-NEXT:    [[ADD:%.*]] = fadd double 0.000000e+00, [[TO_DOUBLE]]
 ; CHECK-NEXT:    [[TO_I32:%.*]] = fptosi double [[ADD]] to i32
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp sgt i32 [[TO_I32]], 300
@@ -202,6 +203,9 @@
 }
 
 ; There's nothing we can do besides going to the full range or overdefined.
+; The initial cast is used with both positive and negative values,
+; so it must remain signed.
+
 define internal i1 @f.fpext(i16 %x) {
 ; CHECK-LABEL: @f.fpext(
 ; CHECK-NEXT:    [[TO_FLOAT:%.*]] = sitofp i16 [[X:%.*]] to float
@@ -232,12 +236,12 @@
 ; There's nothing we can do besides going to the full range or overdefined.
 define i1 @caller.fpext() {
 ; CHECK-LABEL: @caller.fpext(
-; CHECK-NEXT:    [[CALL_1:%.*]] = tail call i1 @f.fpext(i16 100)
+; CHECK-NEXT:    [[CALL_1:%.*]] = tail call i1 @f.fpext(i16 -100)
 ; CHECK-NEXT:    [[CALL_2:%.*]] = tail call i1 @f.fpext(i16 300)
 ; CHECK-NEXT:    [[RES:%.*]] = and i1 [[CALL_1]], [[CALL_2]]
 ; CHECK-NEXT:    ret i1 [[RES]]
 ;
-  %call.1 = tail call i1 @f.fpext(i16 100)
+  %call.1 = tail call i1 @f.fpext(i16 -100)
   %call.2 = tail call i1 @f.fpext(i16 300)
   %res = and i1 %call.1, %call.2
   ret i1 %res
@@ -282,11 +286,10 @@
   ret i1 %res
 }
 
-; Make sure we do not create constant ranges for int to fp casts.
 define i1 @int_range_to_double_cast(i32 %a) {
 ; CHECK-LABEL: @int_range_to_double_cast(
 ; CHECK-NEXT:    [[R:%.*]] = and i32 [[A:%.*]], 255
-; CHECK-NEXT:    [[T4:%.*]] = sitofp i32 [[R]] to double
+; CHECK-NEXT:    [[T4:%.*]] = uitofp i32 [[R]] to double
 ; CHECK-NEXT:    [[T10:%.*]] = fadd double 0.000000e+00, [[T4]]
 ; CHECK-NEXT:    [[T11:%.*]] = fcmp olt double [[T4]], [[T10]]
 ; CHECK-NEXT:    ret i1 [[T11]]
Index: llvm/test/Transforms/SCCP/sitofp.ll
===================================================================
--- llvm/test/Transforms/SCCP/sitofp.ll
+++ llvm/test/Transforms/SCCP/sitofp.ll
@@ -4,7 +4,7 @@
 define float @sitofp_and(i8 %x) {
 ; CHECK-LABEL: @sitofp_and(
 ; CHECK-NEXT:    [[PX:%.*]] = and i8 [[X:%.*]], 127
-; CHECK-NEXT:    [[R:%.*]] = sitofp i8 [[PX]] to float
+; CHECK-NEXT:    [[R:%.*]] = uitofp i8 [[PX]] to float
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %px = and i8 %x, 127
@@ -23,7 +23,7 @@
 define double @sitofp_zext(i7 %x) {
 ; CHECK-LABEL: @sitofp_zext(
 ; CHECK-NEXT:    [[PX:%.*]] = zext i7 [[X:%.*]] to i8
-; CHECK-NEXT:    [[R:%.*]] = sitofp i8 [[PX]] to double
+; CHECK-NEXT:    [[R:%.*]] = uitofp i8 [[PX]] to double
 ; CHECK-NEXT:    ret double [[R]]
 ;
   %px = zext i7 %x to i8
@@ -52,7 +52,7 @@
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i32 [[X:%.*]], 0
 ; CHECK-NEXT:    br i1 [[CMP]], label [[T:%.*]], label [[F:%.*]]
 ; CHECK:       t:
-; CHECK-NEXT:    [[A:%.*]] = sitofp i32 [[X]] to float
+; CHECK-NEXT:    [[A:%.*]] = uitofp i32 [[X]] to float
 ; CHECK-NEXT:    br label [[EXIT:%.*]]
 ; CHECK:       f:
 ; CHECK-NEXT:    br label [[EXIT]]
@@ -86,7 +86,7 @@
 ; CHECK:       t:
 ; CHECK-NEXT:    br label [[EXIT:%.*]]
 ; CHECK:       f:
-; CHECK-NEXT:    [[A:%.*]] = sitofp i32 [[X]] to float
+; CHECK-NEXT:    [[A:%.*]] = uitofp i32 [[X]] to float
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    [[COND:%.*]] = phi float [ -4.200000e+01, [[T]] ], [ [[A]], [[F]] ]