[llvm] [AArch64] Fix variadic tail-calls on ARM64EC (PR #79774)
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Sun Jan 28 17:29:28 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-aarch64
Author: Billy Laws (bylaws)
<details>
<summary>Changes</summary>
ARM64EC varargs calls expect that x4 = sp at entry, special handling is needed to ensure this with tail calls since they occur after the epilogue and the x4 write happens before.
---
Full diff: https://github.com/llvm/llvm-project/pull/79774.diff
2 Files Affected:
- (modified) llvm/lib/Target/AArch64/AArch64ISelLowering.cpp (+12-1)
- (modified) llvm/test/CodeGen/AArch64/vararg-tallcall.ll (+8)
``````````diff
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 332fb37655288ce..18ff1167e1679c7 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -7991,11 +7991,22 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
}
if (IsVarArg && Subtarget->isWindowsArm64EC()) {
+ SDValue ParamPtr = StackPtr;
+ if (IsTailCall) {
+ const AArch64FrameLowering *TFI =
+ MF.getSubtarget<AArch64Subtarget>().getFrameLowering();
+
+ // Create a dummy object at the top of the stack that can be used to get
+ // the SP after the epilogue
+ int FI = MF.getFrameInfo().CreateFixedObject(1, FPDiff, true);
+ ParamPtr = DAG.getFrameIndex(FI, PtrVT);
+ }
+
// For vararg calls, the Arm64EC ABI requires values in x4 and x5
// describing the argument list. x4 contains the address of the
// first stack parameter. x5 contains the size in bytes of all parameters
// passed on the stack.
- RegsToPass.emplace_back(AArch64::X4, StackPtr);
+ RegsToPass.emplace_back(AArch64::X4, ParamPtr);
RegsToPass.emplace_back(AArch64::X5,
DAG.getConstant(NumBytes, DL, MVT::i64));
}
diff --git a/llvm/test/CodeGen/AArch64/vararg-tallcall.ll b/llvm/test/CodeGen/AArch64/vararg-tallcall.ll
index 2d6db1642247d72..812837639196e61 100644
--- a/llvm/test/CodeGen/AArch64/vararg-tallcall.ll
+++ b/llvm/test/CodeGen/AArch64/vararg-tallcall.ll
@@ -1,5 +1,6 @@
; RUN: llc -mtriple=aarch64-windows-msvc %s -o - | FileCheck %s
; RUN: llc -mtriple=aarch64-linux-gnu %s -o - | FileCheck %s
+; RUN: llc -mtriple=arm64ec-windows-msvc %s -o - | FileCheck %s --check-prefixes=CHECK-EC
; RUN: llc -global-isel -global-isel-abort=2 -verify-machineinstrs -mtriple=aarch64-windows-msvc %s -o - | FileCheck %s
; RUN: llc -global-isel -global-isel-abort=2 -verify-machineinstrs -mtriple=aarch64-linux-gnu %s -o - | FileCheck %s
@@ -32,3 +33,10 @@ attributes #1 = { noinline optnone "thunk" }
; CHECK: ldr x9, [x9]
; CHECK: mov v0.16b, v16.16b
; CHECK: br x9
+; CHECK-EC: mov v7.16b, v0.16b
+; CHECK-EC: ldr x9, [x0]
+; CHECK-EC: ldr x11, [x9]
+; CHECK-EC: mov v0.16b, v7.16b
+; CHECK-EC: add x4, sp, #64
+; CHECK-EC: add sp, sp, #64
+; CHECK-EC: br x11
``````````
</details>
https://github.com/llvm/llvm-project/pull/79774
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