Targets: commonize some stack realignment code
This patch does the following:
* Fix FIXME on `needsStackRealignment`: it is now shared between multiple targets, implemented in `TargetRegisterInfo`, and isn't `virtual` anymore. This will break out-of-tree targets, silently if they used `virtual` and with a build error if they used `override`.
* Factor out `canRealignStack` as a `virtual` function on `TargetRegisterInfo`, by default only looks for the `no-realign-stack` function attribute.
Multiple targets duplicated the same `needsStackRealignment` code:
- Aarch64.
- ARM.
- Mips almost: had extra `DEBUG` diagnostic, which the default implementation now has.
- PowerPC.
- WebAssembly.
- x86 almost: has an extra `-force-align-stack` option, which the default implementation now has.
The default implementation of `needsStackRealignment` used to just return `false`. My current patch changes the behavior by simply using the above shared behavior. This affects:
- AMDGPU
- BPF
- CppBackend
- MSP430
- NVPTX
- Sparc
- SystemZ
- XCore
- Out-of-tree targets
This is a breaking change! `make check` passes.
The only implementation of the `virtual` function (besides the slight different in x86) was Hexagon (which did `MF.getFrameInfo()->getMaxAlignment() > 8`), and potentially some out-of-tree targets. Hexagon now uses the default implementation.
`needsStackRealignment` was being overwritten in `<Target>GenRegisterInfo.inc`, to return `false` as the default also did. That was odd and is now gone.
Reviewers: sunfish
Subscribers: aemerson, llvm-commits, jfb
Differential Revision: http://reviews.llvm.org/D11160
llvm-svn: 242727
diff --git a/llvm/test/CodeGen/Generic/ForceStackAlign.ll b/llvm/test/CodeGen/Generic/ForceStackAlign.ll
new file mode 100644
index 0000000..f798fca
--- /dev/null
+++ b/llvm/test/CodeGen/Generic/ForceStackAlign.ll
@@ -0,0 +1,27 @@
+; Check that stack alignment can be forced. Individual targets should test their
+; specific implementation details.
+
+; RUN: llc < %s -force-align-stack -stack-alignment=32 | FileCheck %s
+; CHECK-LABEL: @f
+; CHECK-LABEL: @g
+
+define i32 @f(i8* %p) nounwind {
+entry:
+ %0 = load i8, i8* %p
+ %conv = sext i8 %0 to i32
+ ret i32 %conv
+}
+
+define i64 @g(i32 %i) nounwind {
+entry:
+ br label %if.then
+
+if.then:
+ %0 = alloca i8, i32 %i
+ call void @llvm.memset.p0i8.i32(i8* %0, i8 0, i32 %i, i32 1, i1 false)
+ %call = call i32 @f(i8* %0)
+ %conv = sext i32 %call to i64
+ ret i64 %conv
+}
+
+declare void @llvm.memset.p0i8.i32(i8*, i8, i32, i32, i1) nounwind