[PATCH] D37093: [coroutines] Promote cleanup.dest.slot-like allocas to registers to avoid storing them in the coroutine frame

[Gor Nishanov via Phabricator via llvm-commits]

GorNishanov created this revision.
Herald added subscribers: EricWF, qcolombet.

Allocas that follow the pattern of cleanup.dest.slot, namely, they are
integer allocas that don't escape and only store constants. We don't want
them to be saved into the coroutine frame (as some of the cleanup code may
access them after coroutine frame destroyed).

For example in this coroutine %slot will be promoted to register even in -O0

  define i8* @happy.case() "coroutine.presplit"="1" {
  entry:
    %slot = alloca i32
    %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
    %size = call i32 @llvm.coro.size.i32()
    %alloc = call i8* @malloc(i32 %size)
    %hdl = call i8* @llvm.coro.begin(token %id, i8* %alloc)
  
    store i32 1, i32* %slot
  
    %tok = call i8 @llvm.coro.suspend(token none, i1 false)
    switch i8 %tok, label %suspend [i8 0, label %resume
                                  i8 1, label %cleanup]
  resume:
    store i32 2, i32* %slot
    br label %cleanup
  
  cleanup:
    %mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
    call void @free(i8* %mem)
    %x = load i32, i32* %slot
    call void @print.i32(i32 %x)
    br label %suspend
  suspend:
    call i1 @llvm.coro.end(i8* %hdl, i1 0)
    ret i8* %hdl
  }

This fixes PR34289


https://reviews.llvm.org/D37093

Files:
  lib/Transforms/Coroutines/CoroFrame.cpp
  test/Transforms/Coroutines/coro-spill-promote.ll

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