Bitcast of 64-bit immediates may need to split the immediate, not a var.

tests_lit/llvm2ice_tests/fp.pnacl.ll

 ; This tries to be a comprehensive test of f32 and f64 operations.
 ; The CHECK lines are only checking for basic instruction patterns
 ; that should be present regardless of the optimization level, so
 ; there are no special OPTM1 match lines.
 
 ; RUN: %llvm2ice -O2 --verbose none %s | FileCheck %s
 ; RUN: %llvm2ice -Om1 --verbose none %s | FileCheck %s
 ; RUN: %llvm2ice --verbose none %s | FileCheck --check-prefix=ERRORS %s
 ; RUN: %llvm2iceinsts %s | %szdiff %s | FileCheck --check-prefix=DUMP %s
 ; RUN: %llvm2iceinsts --pnacl %s | %szdiff %s \
@@ skipping 387 matching lines @@
 
 define internal float @unsigned64ToFloat(i64 %a) {
 entry:
   %conv = uitofp i64 %a to float
   ret float %conv
 }
 ; CHECK-LABEL: unsigned64ToFloat
 ; CHECK: call cvtui64tof
 ; CHECK: fstp
 
+define internal double @unsigned64ToDoubleConst() {
+entry:
+  %conv = uitofp i64 12345678901234 to double
+  ret double %conv
+}
+; CHECK-LABEL: unsigned64ToDouble
+; CHECK: push 2874
+; CHECK: push 1942892530
+; CHECK: call cvtui64tod
+; CHECK: fstp
+
 define internal double @signed32ToDouble(i32 %a) {
 entry:
   %conv = sitofp i32 %a to double
   ret double %conv
 }
 ; CHECK-LABEL: signed32ToDouble
 ; CHECK: cvtsi2sd
 ; CHECK: fld
 
 define internal float @signed32ToFloat(i32 %a) {
@@ skipping 694 matching lines @@
   %cond = select i1 %cmp, double %a, double %b
   ret double %cond
 }
 ; CHECK-LABEL: selectDoubleVarVar
 ; CHECK: ucomisd
 ; CHECK: ja .
 ; CHECK: fld
 
 ; ERRORS-NOT: ICE translation error
 ; DUMP-NOT: SZ