[llvm] Spill/restore FP/BP around instructions in which they are clobbered (PR #81048)

[Reid Kleckner via llvm-commits]

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@@ -0,0 +1,52 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc -mtriple=x86_64-pc-linux -stackrealign -verify-machineinstrs < %s | FileCheck %s
+
+; Calling convention ghccc uses ebp to pass parameter, so calling a function
+; using ghccc clobbers ebp. We should save and restore ebp around such a call
+; if ebp is used as frame pointer.
+
+declare ghccc i32 @external(i32)
+
+define i32 @foo(i32 %0, i32 %1) {
+; CHECK-LABEL: foo:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    pushq %rbp
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    .cfi_offset %rbp, -16
+; CHECK-NEXT:    movq %rsp, %rbp
+; CHECK-NEXT:    .cfi_def_cfa_register %rbp
+; CHECK-NEXT:    pushq %r15
+; CHECK-NEXT:    pushq %r14
+; CHECK-NEXT:    pushq %r13
+; CHECK-NEXT:    pushq %r12
+; CHECK-NEXT:    pushq %rbx
+; CHECK-NEXT:    andq $-16, %rsp
+; CHECK-NEXT:    subq $16, %rsp
+; CHECK-NEXT:    .cfi_offset %rbx, -56
+; CHECK-NEXT:    .cfi_offset %r12, -48
+; CHECK-NEXT:    .cfi_offset %r13, -40
+; CHECK-NEXT:    .cfi_offset %r14, -32
+; CHECK-NEXT:    .cfi_offset %r15, -24
+; CHECK-NEXT:    # kill: def $edi killed $edi def $rdi
+; CHECK-NEXT:    pushq %rbp
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    .cfi_remember_state
+; CHECK-NEXT:    .cfi_escape 0x0f, 0x06, 0x77, 0x08, 0x06, 0x11, 0x10, 0x22 #
+; CHECK-NEXT:    movl %esi, %ebp
+; CHECK-NEXT:    movq %rdi, %r13
+; CHECK-NEXT:    callq external at PLT
+; CHECK-NEXT:    addq $8, %rsp
+; CHECK-NEXT:    popq %rbp
+; CHECK-NEXT:    .cfi_restore_state
+; CHECK-NEXT:    leaq -40(%rbp), %rsp
+; CHECK-NEXT:    popq %rbx
+; CHECK-NEXT:    popq %r12
+; CHECK-NEXT:    popq %r13
+; CHECK-NEXT:    popq %r14
+; CHECK-NEXT:    popq %r15
+; CHECK-NEXT:    popq %rbp
+; CHECK-NEXT:    .cfi_def_cfa %rsp, 8
+; CHECK-NEXT:    retq
+    %x = call ghccc i32 @external(i32 %0, i32 %1)
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rnk wrote:

Is there any other calling convention that:
1. clobbers RBX
2. accepts stack arguments

I'd like to exercise the test case where:
* we need to pass stack arguments (num regparm args + 4)
* we have to spill *just* FP (RBP, not RBX)

I'm worried that the stores or pushes to set up the stack arguments will be disturbed by the RBP push and pops.

Regardless of whether the problem exists or not, please add a test case that exercises spilling around a function that clobbers FP/BP with stack arguments.

https://github.com/llvm/llvm-project/pull/81048