Two main goals of this PR are:
* to support "Arithmetic with Overflow" intrinsics, including the
special case when those intrinsics are being generated by the
CodeGenPrepare pass during translations with optimization;
* to redirect intrinsics with aggregate return type to be lowered via
GlobalISel operations instead of SPIRV-specific unfolding/lowering (see
https://github.com/llvm/llvm-project/pull/95012).
There is a new test case
`llvm/test/CodeGen/SPIRV/passes/translate-aggregate-uaddo.ll` that
describes and checks the general logics of the translation.
This PR continues a series of PRs aimed to identify and fix flaws in
code emission, to improve pass rates for the mode with expensive checks
set on (see https://github.com/llvm/llvm-project/pull/101732,
https://github.com/llvm/llvm-project/pull/104104,
https://github.com/llvm/llvm-project/pull/106966), having in mind the
ultimate goal of proceeding towards the non-experimental status of
SPIR-V Backend.
The reproducers are:
1) consider `llc -O3 -mtriple=spirv64-unknown-unknown ...` with:
```
define spir_func i32 @foo(i32 %a, ptr addrspace(4) %p) {
entry:
br label %l1
l1:
%e = phi i32 [ %a, %entry ], [ %i, %body ]
%i = add nsw i32 %e, 1
%fl = icmp eq i32 %i, 0
br i1 %fl, label %exit, label %body
body:
store i8 42, ptr addrspace(4) %p
br label %l1
exit:
ret i32 %i
}
```
2) consider `llc -O0 -mtriple=spirv64-unknown-unknown ...` with:
```
define spir_func i32 @foo(i32 %a, ptr addrspace(4) %p) {
entry:
br label %l1
l1: ; preds = %body, %entry
%e = phi i32 [ %a, %entry ], [ %math, %body ]
%0 = call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %e, i32 1)
%math = extractvalue { i32, i1 } %0, 0
%ov = extractvalue { i32, i1 } %0, 1
br i1 %ov, label %exit, label %body
body: ; preds = %l1
store i8 42, ptr addrspace(4) %p, align 1
br label %l1
exit: ; preds = %l1
ret i32 %math
}
```
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