[llvm-bugs] [Bug 35361] New: [GlobalISel][AArch64] Calling convention for small arguments passed on stack incorrect on big-endian targets

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https://bugs.llvm.org/show_bug.cgi?id=35361

            Bug ID: 35361
           Summary: [GlobalISel][AArch64] Calling convention for small
                    arguments passed on stack incorrect on big-endian
                    targets
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: GlobalISel
          Assignee: unassignedbugs at nondot.org
          Reporter: oliver.stannard at arm.com
                CC: llvm-bugs at lists.llvm.org

Global-isel generates incorrect code when targeting big-endian AArch64 for this
code:
  int foo(int x0, int x1, int x2, int x3, int x4, int x5, int x6, int x7,
          int stack1) {
    return stack1;
  }

  int main() {
    int ret = foo(0,1,2,3,4,5,6,7,8);
    printf("%d\n", ret);
  }

Global isel thinks that the incoming value of stack1 is stored in bytes [0,4)
above SP, but for big-endian targets this should be in bytes [4,8):

// /work/llvm/build/bin/clang --target=aarch64-arm-none-eabi -march=armv8-a -c
callees.cpp -O0 -Wall -std=c++11 -mllvm -global-isel=true -mllvm
-global-isel-abort=0 -mbig-endian -o - -S
_Z3fooiiiiiiiii:                        // @_Z3fooiiiiiiiii
// BB#0:                                // %entry
        sub     sp, sp, #48             // =48
        ldr     w8, [sp, #48]   // <= Should be [sp, #52]
        str     w0, [sp, #44]
        str     w1, [sp, #40]
        str     w2, [sp, #36]
        str     w3, [sp, #32]
        str     w4, [sp, #28]
        str     w5, [sp, #24]
        str     w6, [sp, #20]
        str     w7, [sp, #16]
        str     w8, [sp, #12]
        ldr     w0, [sp, #12]
        add     sp, sp, #48             // =48
        ret

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