Subzero: Align the stack at the point of function calls.

tests_lit/llvm2ice_tests/alloc.ll

-; This is a basic test of the alloca instruction - one test for alloca
-; of a fixed size, and one test for variable size.
+; This is a basic test of the alloca instruction - tests for alloca of
+; a fixed size and for variable size.
 
 ; RUN: %llvm2ice -O2 --verbose none %s | FileCheck %s
-; RUN: %llvm2ice -Om1 --verbose none %s | FileCheck --check-prefix=OPTM1 %s
+; RUN: %llvm2ice -Om1 --verbose none %s | FileCheck %s
 ; RUN: %llvm2ice -O2 --verbose none %s \
 ; RUN:               | llvm-mc -arch=x86 -x86-asm-syntax=intel -filetype=obj
 ; RUN: %llvm2ice -Om1 --verbose none %s \
 ; RUN:               | llvm-mc -arch=x86 -x86-asm-syntax=intel -filetype=obj
 ; 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 \
 ; RUN:                           | FileCheck --check-prefix=DUMP %s
 
 define void @fixed_400(i32 %n) {
 entry:
   %array = alloca i8, i32 400, align 16
   %__2 = ptrtoint i8* %array to i32
   call void @f1(i32 %__2)
   ret void
 }
 ; CHECK: fixed_400:
 ; CHECK:      sub     esp, 400
-; CHECK-NEXT: mov     eax, esp
-; CHECK-NEXT: push    eax
-; CHECK-NEXT: call    f1
-;
-; OPTM1: fixed_400:
-; OPTM1:      sub     esp, 400
-; OPTM1-NEXT: mov     {{.*}}, esp
-; OPTM1:      push
-; OPTM1-NEXT: call    f1
+; CHECK:      sub     esp, 16
+; CHECK:      mov     dword ptr [esp], eax
+; CHECK:      call    f1
+
+define void @fixed_351(i32 %n) {
+entry:
+  %array = alloca i8, i32 351, align 16
+  %__2 = ptrtoint i8* %array to i32
+  call void @f1(i32 %__2)
+  ret void
+}
+; CHECK: fixed_351:
+; CHECK:      sub     esp, 352
+; CHECK:      sub     esp, 16
+; CHECK:      mov     dword ptr [esp], eax
+; CHECK:      call    f1
 
 declare void @f1(i32)
 
 define void @variable_n(i32 %n) {
 entry:
   %array = alloca i8, i32 %n, align 16
   %__2 = ptrtoint i8* %array to i32
   call void @f2(i32 %__2)
   ret void
 }
 ; CHECK: variable_n:
 ; CHECK:      mov     eax, dword ptr [ebp+8]
+; CHECK-NEXT: add     eax, 15
+; CHECK-NEXT: and     eax, 18446744073709551600

[Jim Stichnoth, 2014/08/05 18:09:27]

What is a 64-bit integer immediate doing in an x86-32 program?

[wala, 2014/08/05 23:57:03]

This should be -16. I'm not entirely sure what caused it to be emitted this way.
The current version of the code emits a 32 bit immediate.

 ; CHECK-NEXT: sub     esp, eax
-; CHECK-NEXT: mov     eax, esp
-; CHECK-NEXT: push    eax
-; CHECK-NEXT: call    f2
-;
-; OPTM1: variable_n:
-; OPTM1:      mov     {{.*}}, esp
-; OPTM1:      push
-; OPTM1-NEXT: call    f2
+; CHECK:      sub     esp, 16
+; CHECK:      mov     dword ptr [esp], eax
+; CHECK:      call    f2
 
 declare void @f2(i32)
 
 ; ERRORS-NOT: ICE translation error
 ; DUMP-NOT: SZ