Merge fixed alloca stack adjustments into the prolog

tests_lit/llvm2ice_tests/fused-alloca-arg.ll

 ; This is a basic test of the alloca instruction and a call.
 
 ; RUN: %if --need=target_X8632 --command %p2i --filetype=obj --disassemble \
 ; RUN:   --target x8632 -i %s --args -O2 -allow-externally-defined-symbols \
 ; RUN:   | %if --need=target_X8632 --command FileCheck %s
 
 declare void @copy(i32 %arg1, i8* %arr1, i8* %arr2, i8* %arr3, i8* %arr4);
 
 ; Test that alloca base addresses get passed correctly to functions.
 define internal void @caller1(i32 %arg) {
 entry:
   %a1 = alloca i8, i32 32, align 4
   %p1 = bitcast i8* %a1 to i32*
   store i32 %arg, i32* %p1, align 1
   call void @copy(i32 %arg, i8* %a1, i8* %a1, i8* %a1, i8* %a1)
   ret void
 }
 
 ; CHECK-LABEL:  caller1
-; CHECK-NEXT:   sub    esp,0xc
-; CHECK-NEXT:   mov    eax,DWORD PTR [esp+0x10]
-; CHECK-NEXT:   sub    esp,0x20
-; CHECK-NEXT:   mov    ecx,esp
+; CHECK-NEXT:   sub    esp,0x2c
+; CHECK-NEXT:   mov    eax,DWORD PTR [esp+0x30]
 ; CHECK-NEXT:   mov    DWORD PTR [esp],eax
 ; CHECK-NEXT:   sub    esp,0x20
 ; CHECK-NEXT:   mov    DWORD PTR [esp],eax
 ; CHECK-NEXT:   lea    eax,[esp+0x20]
 ; CHECK-NEXT:   mov    DWORD PTR [esp+0x4],eax
 ; CHECK-NEXT:   lea    eax,[esp+0x20]
 ; CHECK-NEXT:   mov    DWORD PTR [esp+0x8],eax
 ; CHECK-NEXT:   lea    eax,[esp+0x20]
 ; CHECK-NEXT:   mov    DWORD PTR [esp+0xc],eax
 ; CHECK-NEXT:   lea    eax,[esp+0x20]
@@ skipping 10 matching lines @@
   %a2 = alloca i8, i32 32, align 4
   %p1 = bitcast i8* %a1 to i32*
   %p2 = bitcast i8* %a2 to i32*
   store i32 %arg, i32* %p1, align 1
   store i32 %arg, i32* %p2, align 1
   call void @copy(i32 %arg, i8* %a1, i8* %a2, i8* %a1, i8* %a2)
   ret void
 }
 
 ; CHECK-LABEL:  caller2
-; CHECK-NEXT:   sub    esp,0xc
-; CHECK-NEXT:   mov    eax,DWORD PTR [esp+0x10]
-; CHECK-NEXT:   sub    esp,0x40
-; CHECK-NEXT:   mov    ecx,esp
+; CHECK-NEXT:   sub    esp,0x4c
+; CHECK-NEXT:   mov    eax,DWORD PTR [esp+0x50]
 ; CHECK-NEXT:   mov    DWORD PTR [esp],eax
 ; CHECK-NEXT:   mov    DWORD PTR [esp+0x20],eax
 ; CHECK-NEXT:   sub    esp,0x20
 ; CHECK-NEXT:   mov    DWORD PTR [esp],eax
 ; CHECK-NEXT:   lea    eax,[esp+0x20]
 ; CHECK-NEXT:   mov    DWORD PTR [esp+0x4],eax
 ; CHECK-NEXT:   lea    eax,[esp+0x40]
 ; CHECK-NEXT:   mov    DWORD PTR [esp+0x8],eax
 ; CHECK-NEXT:   lea    eax,[esp+0x20]
 ; CHECK-NEXT:   mov    DWORD PTR [esp+0xc],eax
 ; CHECK-NEXT:   lea    eax,[esp+0x40]
 ; CHECK-NEXT:   mov    DWORD PTR [esp+0x10],eax
 ; CHECK-NEXT:   call
 ; CHECK-NEXT:   add    esp,0x20
 ; CHECK-NEXT:   add    esp,0x4c
 ; CHECK-NEXT:   ret