[llvm] 0e63180 - Reapply "[Aarch64] [ISel] Don't save vaargs registers if vaargs are unused" (#131459)
via llvm-commits
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Mon Mar 24 08:13:46 PDT 2025
Author: Pavel Skripkin
Date: 2025-03-24T18:13:42+03:00
New Revision: 0e63180fa3e130c7da304578d29631c847fdcd62
URL: https://github.com/llvm/llvm-project/commit/0e63180fa3e130c7da304578d29631c847fdcd62
DIFF: https://github.com/llvm/llvm-project/commit/0e63180fa3e130c7da304578d29631c847fdcd62.diff
LOG: Reapply "[Aarch64] [ISel] Don't save vaargs registers if vaargs are unused" (#131459)
This reapplies original commit e122483762b44c7f4386165099ff2a404705d7d4
Second try, but with win64 removed from the scope, since it was somehow
broken by original commit.
### Original PR description
If vaargs are not used there is no need to save them. LLVM already
implements such optimization for x86, as well as gcc [1].
Some ABI tests are kept almost as-is, except for stack offsets, by just
adding llvm.va_start. Only laapcs_vararg_frame.ll test was rewritten to
match new behavior.
[1] https://godbolt.org/z/GWWKr8xMd
Added:
Modified:
llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
llvm/test/CodeGen/AArch64/GlobalISel/aapcs_vararg_frame.ll
llvm/test/CodeGen/AArch64/alloca.ll
llvm/test/CodeGen/AArch64/darwinpcs-tail.ll
llvm/test/CodeGen/AArch64/vararg-tallcall.ll
Removed:
################################################################################
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 3a45802b24cc1..d0f51b73a4a44 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -8241,7 +8241,10 @@ SDValue AArch64TargetLowering::LowerFormalArguments(
}
// varargs
- if (isVarArg) {
+ // Note that IsWin64 part is required to prevent odd miscompilations on arm64
+ // windows platforms. For more info refer to GH#126780 PR comments.
+ if (isVarArg &&
+ (DAG.getMachineFunction().getFrameInfo().hasVAStart() || IsWin64)) {
if (!Subtarget->isTargetDarwin() || IsWin64) {
// The AAPCS variadic function ABI is identical to the non-variadic
// one. As a result there may be more arguments in registers and we should
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/aapcs_vararg_frame.ll b/llvm/test/CodeGen/AArch64/GlobalISel/aapcs_vararg_frame.ll
index 7892e892a2412..6ea520ddcd6cd 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/aapcs_vararg_frame.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/aapcs_vararg_frame.ll
@@ -2,19 +2,11 @@
; RUN: llc < %s --global-isel=0 -mtriple=aarch64-linux-gnu -mattr=+fp-armv8 | FileCheck %s
; RUN: llc < %s --global-isel=1 -mtriple=aarch64-linux-gnu -mattr=+fp-armv8 | FileCheck %s --check-prefix=GISEL
+%struct.__va_list = type { ptr, ptr, ptr, i32, i32 }
+
define void @va(i32 %count, half %f, ...) nounwind {
; CHECK-LABEL: va:
; CHECK: // %bb.0: // %entry
-; CHECK-NEXT: sub sp, sp, #176
-; CHECK-NEXT: stp x2, x3, [sp, #128]
-; CHECK-NEXT: str x1, [sp, #120]
-; CHECK-NEXT: stp x4, x5, [sp, #144]
-; CHECK-NEXT: stp x6, x7, [sp, #160]
-; CHECK-NEXT: stp q1, q2, [sp]
-; CHECK-NEXT: stp q3, q4, [sp, #32]
-; CHECK-NEXT: stp q5, q6, [sp, #64]
-; CHECK-NEXT: str q7, [sp, #96]
-; CHECK-NEXT: add sp, sp, #176
; CHECK-NEXT: ret
;
; GISEL-LABEL: va:
@@ -33,3 +25,55 @@ define void @va(i32 %count, half %f, ...) nounwind {
entry:
ret void
}
+
+define void @va_used(i32 %count, half %f, ...) nounwind {
+; CHECK-LABEL: va_used:
+; CHECK: // %bb.0:
+; CHECK-NEXT: sub sp, sp, #208
+; CHECK-NEXT: mov x8, #-56 // =0xffffffffffffffc8
+; CHECK-NEXT: mov x9, sp
+; CHECK-NEXT: add x10, sp, #120
+; CHECK-NEXT: movk x8, #65424, lsl #32
+; CHECK-NEXT: add x9, x9, #112
+; CHECK-NEXT: stp x2, x3, [sp, #128]
+; CHECK-NEXT: stp x9, x8, [sp, #192]
+; CHECK-NEXT: add x8, x10, #56
+; CHECK-NEXT: add x9, sp, #208
+; CHECK-NEXT: str x1, [sp, #120]
+; CHECK-NEXT: stp x4, x5, [sp, #144]
+; CHECK-NEXT: stp x6, x7, [sp, #160]
+; CHECK-NEXT: stp q1, q2, [sp]
+; CHECK-NEXT: stp q3, q4, [sp, #32]
+; CHECK-NEXT: stp q5, q6, [sp, #64]
+; CHECK-NEXT: str q7, [sp, #96]
+; CHECK-NEXT: stp x9, x8, [sp, #176]
+; CHECK-NEXT: add sp, sp, #208
+; CHECK-NEXT: ret
+;
+; GISEL-LABEL: va_used:
+; GISEL: // %bb.0:
+; GISEL-NEXT: sub sp, sp, #208
+; GISEL-NEXT: mov x8, sp
+; GISEL-NEXT: add x9, sp, #208
+; GISEL-NEXT: add x10, sp, #208
+; GISEL-NEXT: stp x9, x10, [x8]
+; GISEL-NEXT: add x9, sp, #144
+; GISEL-NEXT: mov w10, #-112 // =0xffffff90
+; GISEL-NEXT: str x9, [x8, #16]
+; GISEL-NEXT: mov w9, #-56 // =0xffffffc8
+; GISEL-NEXT: stp x1, x2, [sp, #152]
+; GISEL-NEXT: stp x3, x4, [sp, #168]
+; GISEL-NEXT: stp x5, x6, [sp, #184]
+; GISEL-NEXT: str x7, [sp, #200]
+; GISEL-NEXT: stp q1, q2, [sp, #32]
+; GISEL-NEXT: stp q3, q4, [sp, #64]
+; GISEL-NEXT: stp q5, q6, [sp, #96]
+; GISEL-NEXT: str q7, [sp, #128]
+; GISEL-NEXT: stp w9, w10, [x8, #24]
+; GISEL-NEXT: add sp, sp, #208
+; GISEL-NEXT: ret
+ %valist = alloca %struct.__va_list
+ call void @llvm.va_start(ptr %valist)
+ call void @llvm.va_end(ptr %valist)
+ ret void
+}
diff --git a/llvm/test/CodeGen/AArch64/alloca.ll b/llvm/test/CodeGen/AArch64/alloca.ll
index ca3a500d79f32..119b84e352c74 100644
--- a/llvm/test/CodeGen/AArch64/alloca.ll
+++ b/llvm/test/CodeGen/AArch64/alloca.ll
@@ -62,6 +62,8 @@ define i64 @test_alloca_with_local(i64 %n) {
; CHECK: ret
}
+%struct.__va_list = type { ptr, ptr, ptr, i32, i32 }
+
define void @test_variadic_alloca(i64 %n, ...) {
; CHECK-LABEL: test_variadic_alloca:
@@ -77,31 +79,33 @@ define void @test_variadic_alloca(i64 %n, ...) {
; CHECK: stp x29, x30, [sp, #-16]!
; CHECK: mov x29, sp
-; CHECK: sub sp, sp, #192
-; CHECK-DAG: stp q6, q7, [x29, #-96]
+; CHECK: sub sp, sp, #224
+; CHECK-DAG: stp q6, q7, [x29, #-128]
; [...]
-; CHECK-DAG: stp q0, q1, [x29, #-192]
+; CHECK-DAG: stp q2, q3, [x29, #-192]
-; CHECK-DAG: stp x5, x6, [x29, #-24]
+; CHECK-DAG: stp x5, x6, [x29, #-56]
; [...]
-; CHECK-DAG: stp x1, x2, [x29, #-56]
+; CHECK-DAG: stp x1, x2, [x29, #-88]
; CHECK-NOFP-ARM64: stp x29, x30, [sp, #-16]!
; CHECK-NOFP-ARM64: mov x29, sp
-; CHECK-NOFP-ARM64: sub sp, sp, #64
-; CHECK-NOFP-ARM64-DAG: stp x5, x6, [x29, #-24]
+; CHECK-NOFP-ARM64: sub sp, sp, #16
+; CHECK-NOFP-ARM64-DAG: stp x5, x6, [x29, #-56]
; [...]
-; CHECK-NOFP-ARM64-DAG: stp x3, x4, [x29, #-40]
+; CHECK-NOFP-ARM64-DAG: stp x3, x4, [x29, #-72]
; [...]
-; CHECK-NOFP-ARM64-DAG: stp x1, x2, [x29, #-56]
+; CHECK-NOFP-ARM64-DAG: stp x1, x2, [x29, #-88]
; [...]
; CHECK-NOFP-ARM64: mov x8, sp
-
+ %valist = alloca %struct.__va_list
+ call void @llvm.va_start(ptr %valist)
%addr = alloca i8, i64 %n
call void @use_addr(ptr %addr)
; CHECK: bl use_addr
+ call void @llvm.va_end(ptr %valist)
ret void
; CHECK-NOFP-AARCH64: sub sp, x29, #64
diff --git a/llvm/test/CodeGen/AArch64/darwinpcs-tail.ll b/llvm/test/CodeGen/AArch64/darwinpcs-tail.ll
index 5d3c755d0d73d..da176894c48a9 100644
--- a/llvm/test/CodeGen/AArch64/darwinpcs-tail.ll
+++ b/llvm/test/CodeGen/AArch64/darwinpcs-tail.ll
@@ -8,8 +8,8 @@
; CHECK-LABEL: _tailTest:
; CHECK: b __ZN1C3addEPKcz
; CHECK-LABEL: __ZThn8_N1C1fEiiiiiiiiiz:
-; CHECK: ldr w9, [sp, #4]
-; CHECK: str w9, [sp, #4]
+; CHECK: ldr w8, [sp, #4]
+; CHECK: str w8, [sp, #4]
; CHECK: b __ZN1C1fEiiiiiiiiiz
%class.C = type { %class.A.base, [4 x i8], %class.B.base, [4 x i8] }
diff --git a/llvm/test/CodeGen/AArch64/vararg-tallcall.ll b/llvm/test/CodeGen/AArch64/vararg-tallcall.ll
index 812837639196e..7ee76c8ad50a2 100644
--- a/llvm/test/CodeGen/AArch64/vararg-tallcall.ll
+++ b/llvm/test/CodeGen/AArch64/vararg-tallcall.ll
@@ -8,18 +8,22 @@ target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
%class.X = type { i8 }
%struct.B = type { ptr }
+%struct.__va_list = type { ptr, ptr, ptr, i32, i32 }
$"??_9B@@$BA at AA" = comdat any
; Function Attrs: noinline optnone
define linkonce_odr void @"??_9B@@$BA at AA"(ptr %this, ...) #1 comdat align 2 {
entry:
+ %valist = alloca %struct.__va_list
+ call void @llvm.va_start.p0(ptr %valist)
%this.addr = alloca ptr, align 8
store ptr %this, ptr %this.addr, align 8
%this1 = load ptr, ptr %this.addr, align 8
call void asm sideeffect "", "~{d0}"()
%vtable = load ptr, ptr %this1, align 8
%0 = load ptr, ptr %vtable, align 8
+ call void @llvm.va_end.p0(ptr %valist)
musttail call void (ptr, ...) %0(ptr %this1, ...)
ret void
; No predecessors!
@@ -36,7 +40,9 @@ attributes #1 = { noinline optnone "thunk" }
; CHECK-EC: mov v7.16b, v0.16b
; CHECK-EC: ldr x9, [x0]
; CHECK-EC: ldr x11, [x9]
+; CHECH-EC: add x4, sp, #96
; CHECK-EC: mov v0.16b, v7.16b
-; CHECK-EC: add x4, sp, #64
-; CHECK-EC: add sp, sp, #64
+; CHECK-EC: add x4, sp, #96
+; CHECK-EC: ldr x30, [sp, #48]
+; CHECK-EC: add sp, sp, #96
; CHECK-EC: br x11
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