[llvm] [win][x64] Allow push/pop for stack alloc when unwind v2 is required (PR #153621)

[Daniel Paoliello via llvm-commits]

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@@ -0,0 +1,80 @@
+; RUN: llc -mtriple=x86_64-unknown-windows-msvc -o - %s | FileCheck %s
+
+; Regression test for Win x64 unwind v2: in some cases it is better to use
+; push+pop to adjust the stack, rather than sub+add. This is permitted with
+; unwind v2 as the requirement is that the epilog finishes adjusting the stack
+; before popping the registers listed in the unwind table.
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dpaoliello wrote:

Good idea

https://github.com/llvm/llvm-project/pull/153621