The instruction selection pass for SPIR-V now performs dead code
elimination (DCE).
This change removes unused instructions, leading to more optimized
SPIR-V output.
As a consequence of this, several tests were updated to ensure their
continued
correctness and to prevent previously tested code from being optimized
away.
Specifically:
- Many tests now store computed values into global variables to ensure
they are
not eliminated by DCE, allowing their code generation to be verified.
- The test `keep-tracked-const.ll` was removed because it no longer
tested
its original intent. The check statements in this test were for
constants
generated when expanding a G_TRUNC instruction, which is now removed by
DCE
instead of being expanded.
- A new test, `remove-dead-type-intrinsics.ll`, was added to confirm
that dead
struct types are correctly removed by the compiler.
These updates improve the SPIR-V backends optimization capabilities and
maintain the robustness of the test suite.
---------
Co-authored-by: Nathan Gauër <github@keenuts.net>
This commit enables a pass in the backend which propagates the addrspace
of the pointers down to the last use, making sure the addrspace remains
consistent, and thus stripping any addrspacecast. This is required to
lower LLVM-IR to logical SPIR-V, which does not support generic
pointers.
This is now required as HLSL emits several address spaces, and thus
addrspacecasts in some cases:
Example 1: resource access
```llvm
%handle = tail call target("spirv.VulkanBuffer", ...)
%rptr = @llvm.spv.resource.getpointer(%handle, ...);
%cptr = addrspacecast ptr addrspace(11) %rptr to ptr
%fptr = load i32, ptr %cptr
```
Example 2: object methods
```llvm
define void @objectMethod(ptr %this) {
}
define void @foo(ptr addrspace(11) %object) {
call void @objectMethod(ptr addrspacecast(addrspace(11) %object to ptr));
}
```
