Multiple fixes / improvements for LLVM backend

- Fix for #13904 -- stop "trashing" callee-saved registers, since it is
  not actually doing anything useful.

- Fix for #14251 -- fixes the calling convention for functions passing
  raw SSE-register values by adding padding as needed to get the values
  in the right registers. This problem cropped up when some args were
  unused an dropped from the live list.

- Fixed a typo in 'readnone' attribute

- Added 'lower-expect' pass to level 0 LLVM optimization passes to
  improve block layout in LLVM for stack checks, etc.

Test Plan: `make test WAYS=optllvm` and `make test WAYS=llvm`

Reviewers: bgamari, simonmar, angerman

Reviewed By: angerman

Subscribers: rwbarton, carter

GHC Trac Issues: #13904, #14251

Differential Revision: https://phabricator.haskell.org/D5190

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm-passes b/llvm-passes
index 5183c9f2ab..14eb62d87c 100644
--- a/llvm-passes
+++ b/llvm-passes
@@ -1,5 +1,5 @@
 [
-(0, "-mem2reg -globalopt"),
+(0, "-mem2reg -globalopt -lower-expect"),
 (1, "-O1 -globalopt"),
 (2, "-O2")
 ]