[llvm-bugs] [Bug 35345] New: Invalid assembly for huge stack frame

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=35345

            Bug ID: 35345
           Summary: Invalid assembly for huge stack frame
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: dan433584 at gmail.com
                CC: llvm-bugs at lists.llvm.org

Compiling this C code with clang for 32-bit x86:

#include <stdint.h>

void foo(char*, char*, char*, char*);

void bar(void) {
    char a[INT32_MAX/1];
    char b[INT32_MAX/1];
    char c[INT32_MAX/1];
    char d[INT32_MAX/1];
    foo(a, b, c, d);
}

I get no warnings and this LLVM IR:

[...]
define void @bar() #0 {
  %1 = alloca [2147483647 x i8], align 1
  %2 = alloca [2147483647 x i8], align 1
  %3 = alloca [2147483647 x i8], align 1
  %4 = alloca [2147483647 x i8], align 1
  %5 = getelementptr inbounds [2147483647 x i8], [2147483647 x i8]* %1, i32 0,
i32 0
  %6 = getelementptr inbounds [2147483647 x i8], [2147483647 x i8]* %2, i32 0,
i32 0
  %7 = getelementptr inbounds [2147483647 x i8], [2147483647 x i8]* %3, i32 0,
i32 0
  %8 = getelementptr inbounds [2147483647 x i8], [2147483647 x i8]* %4, i32 0,
i32 0
  call void @foo(i8* %5, i8* %6, i8* %7, i8* %8)
  ret void
}
[...]

and this prologue in the output:

[...]
        pushl   %ebp
        movl    %esp, %ebp
        pushl   %esi
        movl    $8589934612, %eax       # imm = 0x200000014
        subl    %eax, %esp
[...]

8589934612 does not fit into a 32-bit immediate, though llvm-mc silently wraps
it so that it does, producing miscompiled output.

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