Reserve space for scalar FP returns in the stack frame

tests_lit/llvm2ice_tests/commutativity.ll

 ; Test the lowering sequence for commutative operations.  If there is a source
 ; operand whose lifetime ends in an operation, it should be the first operand,
 ; eliminating the need for a move to start the new lifetime.
 
 ; RUN: %if --need=target_X8632 --command %p2i --filetype=obj --disassemble \
 ; RUN:   --target x8632 -i %s --args -O2 \
 ; RUN:   | %if --need=target_X8632 --command FileCheck %s
 
 define internal i32 @integerAddLeft(i32 %a, i32 %b) {
 entry:
@@ skipping 43 matching lines @@
 ; CHECK-NEXT: imul {{e..}},{{e..}}
 ; CHECK-NEXT: imul {{e..}},{{e..}}
 
 define internal float @floatAddLeft(float %a, float %b) {
 entry:
   %tmp = fadd float %a, %b
   %result = fadd float %a, %tmp
   ret float %result
 }
 ; CHECK-LABEL: floatAddLeft
+; CHECK-NEXT: sub esp,0xc
 ; CHECK-NEXT: movss xmm0,DWORD PTR
 ; CHECK-NEXT: movss xmm1,DWORD PTR
 ; CHECK-NEXT: addss xmm1,xmm0
 ; CHECK-NEXT: addss xmm0,xmm1
 
 define internal float @floatAddRight(float %a, float %b) {
 entry:
   %tmp = fadd float %a, %b
   %result = fadd float %b, %tmp
   ret float %result
 }
 ; CHECK-LABEL: floatAddRight
+; CHECK-NEXT: sub esp,0xc
 ; CHECK-NEXT: movss xmm0,DWORD PTR
 ; CHECK-NEXT: movss xmm1,DWORD PTR
 ; CHECK-NEXT: addss xmm0,xmm1
 ; CHECK-NEXT: addss xmm1,xmm0
 
 define internal float @floatMultiplyLeft(float %a, float %b) {
 entry:
   %tmp = fmul float %a, %b
   %result = fmul float %a, %tmp
   ret float %result
 }
 ; CHECK-LABEL: floatMultiplyLeft
+; CHECK-NEXT: sub esp,0xc
 ; CHECK-NEXT: movss xmm0,DWORD PTR
 ; CHECK-NEXT: movss xmm1,DWORD PTR
 ; CHECK-NEXT: mulss xmm1,xmm0
 ; CHECK-NEXT: mulss xmm0,xmm1
 
 define internal float @floatMultiplyRight(float %a, float %b) {
 entry:
   %tmp = fmul float %a, %b
   %result = fmul float %b, %tmp
   ret float %result
 }
 ; CHECK-LABEL: floatMultiplyRight
+; CHECK-NEXT: sub esp,0xc
 ; CHECK-NEXT: movss xmm0,DWORD PTR
 ; CHECK-NEXT: movss xmm1,DWORD PTR
 ; CHECK-NEXT: mulss xmm0,xmm1
 ; CHECK-NEXT: mulss xmm1,xmm0